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Reports Utah Water Research Laboratory

January 1980

Flood Damage Mitigation in Utah

L. Douglas James

Dean T. Larson

Daniel H. Hoggan

Terrence L. Glover

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Recommended Citation James, L. Douglas; Larson, Dean T.; Hoggan, Daniel H.; and Glover, Terrence L., "Flood Damage Mitigation in Utah" (1980). Reports. Paper 326. https://digitalcommons.usu.edu/water_rep/326

This Report is brought to you for free and open access by the Utah Water Research Laboratory at DigitalCommons@USU. It has been accepted for inclusion in Reports by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. Flood Damage Mitigation in Utah

L. Douglas James Dean T. Larson Daniel H. Hoggan Terrence L. Glover

Utah Water Research Laboratory Utah State University Logan, Utah 84322 WA TER RESOURCES PLANNING SERIES January 1980 UWRL/P-80/0 1 COVER

During the night of January 20, 1980 (while this report was being typed) heavy rains on frozen ground in northern Utah caused extensive flash flooding in Cache and Box Elder Counties. The damages were con­ centrated in the communities at the base of the Wellsville Mountains and smaller ranges to the north. Mendon was the worst hit community, and the flooding there was compounded by water collecting in an irri­ gation canal which broke in several places causing deep washes. The total damage in the two count ies was about $3 million with 43 percent occurring to roads a~d bridges, 29 percent to land and livestock, and 28 percent to irrigation and other water control systems. Counts of water in up to 200 basements were reported, but no figures on damages to homes were published and indications are that they are a relatively small portion of the total. The pictures on the cover illustrate the kinds of damages caused by a flash flood·in rural Utah. During. the week of February 17, 1980, another .series of heavy rains caused repeat flooding, particularly concentrated in Mendon and Clarkston, that caused a similar amount of damage. FLOOD DAMAGE MITIGATION IN UTAH

L. Douglas James Dean T. Larson Daniel H. Hoggan Terrence L. Glover

WATER RESOURCES PLANNING SERIES UWRLjP-80/01

Utah Water Research Laboratory Utah State University Logan, Utah 84322

January 1980 ABSTRACT

Utah is subjected to flash flooding in mountain canyons, mudflows and shallow water flooding on lowlands at the canyon outlets, storm water flooding after thunderstorms in urban areas, and prolonged periods of inundation in certain lowland areas during snowmelt peri­ ods. In response to these problems, individuals are making private land use and flood proofing decisions, larger communities have storm water collection programs, three federal agencies are involved in structural flood control, and the Federal Emergency Management Agency is manqging a National Flood Insurance Program designed to promote community floodplain management efforts. A framework was developed of the dynamically interactive feedback process through which people at various levels and from various prospectives seek the benefits of floodplain occupancy, experience floods, and respond by changing their occupancy or the flows. That framework then became the background for identifying what state government should do in Utah to correct unsatisfactory aspects of the existing flood hazard and counter measures. The data used in the analysis included magnitudes of major historical snowfall and precipitation events, estimates of 100-year flows for all 105 gaged locations with more than 20 years of record, envelope curves of 100-year flow versus drainage area for Utah basins, descriptions of the major historical floods (by order according to amount of damage 1. Salt Lake City canyons 1952 $6,74,000; 2. Ogden 1979 $1,000,000; 3. Virgin River 1966 $962,000; 4. Sheep Creek (Dag­ gett County) 1965 $802,000), descriptions of the structural flood control projects built or being planned in Utah by the Corps of Engineers, Soil Conservation Service, and Water and Power Resources Service, data with respect to participation in the national flood insurance program of Utah I s 251 communit ies, a survey of the flood hazard in 32 of those communities randomly selected from a stratified sample, and a detailed evaluation of the situations in 7 of them. The study found that the flood hazard in Utah is much more concentrated in smaller basins than is so for other parts of the country and that the major problem lies at the base of the mountains where major damages are regularly being caused by flows at mountain hollows too small for hazard areas to have been mapped through the National Flood Insurance Program. Better methodology needs to be developed and applied for delineating hazard areas from mudflows and shallow water flooding on alluvial fans and other lowlands at the mountain base. Attention needs to be given to the effects of irriga­ t ion canals and bridges on the risk. Designs need to be developed that work with nature in disperSing the flood water and recharging much of it to underground aquifers instead rather than against nature in concentrating the flows in a downstream direction.

State actions recommended include 1) providing a continuing forum for interaction among federal agencies and local communItIes, 2) providing technical support for local communities including review of proposed designs for safety, 3) developing structural and flood proofing designs that will be effective in Utah conditions, and 4) interacting with federal agencies on behalf of the local communities.

iii ACKNOWLEDGMENTS

This project was completed at the Utah Water Research Laboratory with funding provided through its state appropriation (WA33) to study priority problems identified by its Citizen Advisory Council. The authors are also indebted to the support they received from the Utah Division of Water Resources, the Federal Emergency Management Agency, and the 35' Utah communities from which data for the study were col­ lected.

iv TABLE OF CONTENTS

Chapter Page

I THE ROLE OF STATE FLOOD CONTROL PROGRAMS 1

The Flood Control Planning Framework 1 The Floodplain Land Use Context 1 A Focus on Flood Problems in Utah 2 Approaches to Flood Hazard Reduction . . . . 2 Roles of the PrinCipal Flood Control Institutions 2 Role Interaction in the Existing Program 3 Historical Role Development 3 The Federal Influencing Mode 3 State and Local Influencing Modes 5 Guidelines for Formulating a State Program 5 Study Objectives 5 Study Organization 5 II A CONCEPTUAL FRAMEWORK FOR DEFINING A STATE PROGRAM 7 Introduction 7 Components of the Conceptual Framework 7 Initial Conditions 7 The Stimulus 7 Consequences 7 Levels of Impact 8 Dimensions of Impact 8 Loci of Decision Making 9 Alternatives 9 Relevant Information . 10 Guidance for Decision Making 10 Differences Among Decision Loci 11 Limitations in Use of Guidance 11 Differences in Information Used 11 Elements of Perspective . 13 Classification of Conflict Sources 14 Decision Dynamics 14 Overview . 14 Flood Impacts 15 Flood Control Program Impacts 16 Foundations for a Utah Perspective 17 Current State Program. . . . 17 Basis for Long Run Objectives . 18 Perspective for Recognizing Salient Issues 18 Perspective for Flood Program Operation 19 III FLOOD HAZARD IN UTAH 21 Introduction 21 Major Precipitation Events 21 Major Recorded Runoff Events 23 Regional Flood Frequency Studies 24

v -.~. TABLE OF CONTENTS (CONTINUED)

Chapter Page Flood Peaks Estimated from Precipitation . 24 Descriptive Information on Historical Floods 25 Hydraulic Analysis . 32 Design Ramifications 33 IV FLOOD CONTROL IN UTAH 35 Introduction. . . . 35 Federal Structural Flood Control Measures 35 U.S. Army Corps of Engineers ... 35 Water and Power Resources Service (Bureau of Reclamation). . 36 Soil Conservation Service 36 Program Assessments ...... 36 City and County Structural Flood Control Measures. 40 The National Flood Insurance Program . 40 Program History . 40 Community Requirements and Program Coverage 41 Community Floodplain Management Programs 43 Floodplain Occupancy Choices 52

V SURVEY OF FLOOD PROBLEMS 53 Survey Approach. . 53 Sampling Procedure . 53 Information Sought by Community 53 Findings for Counties 56 Box Elder County 56 Cache County . 57 Emery County . 58 Piute County . 59 Uintah County 60 Washington County 61 Findings for Towns and Cities 63 Beaver . 63 Bluff . 63 Bountiful 63 Castle Dale 65 Corinne 66 East Layton 66 Garden City 66 Garland 67 Helper. 67 Hurricane 68 Hyde Park 68 Kamas 69 Kingston 69 Koosharem 69 Midway. 70 Millville 70 Ogden 71 Parowan 73 Pleasant Grove 74 Provo 75 Richmond 76 Sandy 77 Spanish Fork 78 Wales 78 Washington Terrace 79 West Point 79

vi TABLE OF CONTENTS (CONTINUED)

Chapter Page Summary of Survey Findings 79 Differences Among Community Types 79 Principal Identified Problems 80 VI ANALYSIS OF FLOOD PROBLEMS 81 Introduction...... 81 Classification of Flood Program Problem Types 81 Selection of Communities for Analysis 81 Bountiful . 82 Brigham City 84 Helper 87 Moab 88 Ogden 91 Provo 92 Willard 94 Statement of Problems Identified 96 VII EVALUATION OF PROGRAMS AND RECOMMENDATIONS 97 Introduction...... 97 Evaluation of Adequacy of Flood Hazard Information ...... 97 Evaluation of Effectiveness of Flood Control Activity . . 98 Impact Evaluation from a Utah Perspective 99 Recommendations on Potential State Actions 100 Research Recommendations 101 REFERENCES 103

vii LIST OF FIGURES

Figure Page 1 Impact dimensions of an implemented action 8 2 Feasibility issues by impact dimension 10 3 Conceptualization of overlapping information sets 12 4 Conflict types associated with various differences in elements of perception 14 5 Location map for record snowpack accumulations (S), precipitation amounts (P), and stream __ al flows (Q) . 22

6 Maximum precipitation recorded in Utah for various durations . 24 7 Normalized Depth-Area-Duration Curve derived by enveloping project cloudburst data (6-hour) 25 8 100-year flows calculated for Utah drainage basins with 20 or more years of record. 29

9 Typical floodplain management ordinance 51 10 Location map for sample communities 55 11 Flood hazard on a segment of Barton Creek in Bountiful (from FIA detailed study, 1978) 65 12 Map of Bountiful and West Bountiful 82 13 Brigham City flood hazard area 85 14 Helper flood hazard area 88 15 Moab flood hazard area· 89 16 Flood damage in downtown Moab 90 17 Debris basin on 27th Street, Ogden, Utah 92 18 Map of Provo 94 19 Map of Willard 95 20 Small canyon watersheds above Willard 96

ix LIST OF TABLES

Table Page

1 Record Utah snowpack accumulations (for stations with over 40 years of record) . 21

2 Record 24-hour precipitation amounts for Utah (for selected stations with 55 years or more of record) 23

3 Record gaged streamflow in Utah (flows of record at all sites with more than 20 years of gaged record) 26

4 Flood insurance study flood peaks estimated for selected Utah drainage basins 30

5 U.S. Army Corps of Engineers floodplain information studies 35

6 Federally sponsored flood control measures in Utah 37

7 Emergency work--Corps of Engineers 39

8 Phases of participation in the Flood Insurance Program 42

9 Maximum amounts of insurance available 43

10 Population and flood insurance participation of Utah counties and incorporated cities and towns . 44

11 Number of Utah communities by code classification 50

12 Study sample communities . 54

13 Summary of flood flows in Provo 76

14 Obstructive bridges and culverts 86

15 Estimates of the instantaneous peak discharge for Mill and Pack Creeks near Moab, Utah 89

x CHAPTER I THE ROLE OF STATE FLOOD CONTROL PROGRAMS

The Flood Control Planning Framework ment, the individuals making floodplain occupancy decisions, and the local govern­ Even though annual damage rates in Utah ments in flood prone areas. Furthermore, are only about 20 percent of the nat ionwide these groups do not have equal status and average, flooding is still a significant resources in resolving preference clashes or problem for the state. Flash floods rise differences ar is ing dur ing plan implementa­ quickly to destroy property and take lives in tion. One objective of this report is to mountain canyons and on the alluvial fans at determine whether there is a role for state their base. Melting snowpacks prolong runoff government in establishing planning criteria out of the canyons and add to the damage in and achieving conflict resolutions more the communities below. Thunderstorms in equitable for Utah situations. urban areas cause drainage problems and widespread rainstorms bring larger streams to their highest peaks. In short, the problem The Floodplain Land Use Context is definitely severe enough to require -remedial activity. The flood control and floodplain manage­ ment ideal is for a responsible planning unit Individuals can do much (site selection, to identify the optimal mix of structural and building construction methods, evacuation, nonstructural measures and proceed to imple­ etc.) to protect themselves and their proper­ ment them. In pract ice, planned solut ions ty, but protection can often be achieved more to flood problems are seldom truly optimal economically through collect ive act ion. For because of limitations to the information example, a dam or a levee is much more and analytic capability available to plan­ effective and economical than flood proofing ners. A generally far more limiting obstacle each building in a town. Federal programs to achieving the desired flood damage reduc­ were consequently established to provide the t ion, however, is that planning author it ies needed collect ive effort, but sole reliance do not control the groups that must work on structural measures was found to be far together in implementing land use,flood more expensive than the national budget could proofing, and emergency measures. afford. The response at the federal level h as been to move toward supplement al regu­ The fact is that the flood damage latory efforts to restrict floodplain devel­ reduction a planning authority can achieve is opment. Conceptually, no expens ive protec­ limited by the presence of many individuals tion would be required, and no flood damages and groups thrQughout society independently would occur if no property were exposed. making and implementing decisions that Regulation, however, limits the freedom of directly or indirectly affect and collective­ individuals to develop their land and is ly determine flood hazard, floodplain land . prone to become unnecessarily restrictive. use, and human response to flood emergencies. Certainly in Utah, where average annual Some of these act ions alleviate flood prob­ flood damages are low on the nat ional scale lems but others, inadvertently or in combina­ and the character of the flooding is not tion with simultaneous unanticipated actions typical, as can be seen from the above by others, worsen them. Some alleviate from examples, regulatory efforts must be designed the viewpoint of those implementing them but to accommodate local needs to avoid becoming are harmful from the viewpoints of others. more restrictive than can be justified. The cumulative effect is a de facto, as opposed to an object ively planned s ituat ion An effective flood program must be with respect to the number of lives and planned. The ideal planning framework is to amount of property at risk. I f nat ional examlne the physical, economic, ecologic, flood losses are too high, this de facto social and other aspects of each flood situation must be changed. problem and propose a plan of action best suited for the specific local situation. Utah government has the opportunity to The result would be an optimal mix of struc­ alter this de facto situation to achieve tural and regulatory (nonstructural) measures state goals. Converting this opportunity and defined governmental actions to implement into an operational program, however, poses them. The use of local information is several challenging issues. How can a necessary but not sufficient for doing a good conceptually tractable state viewpoint and an job because determination of the best suited effective action role for implementing it be plan requires objective criteria. Goal def ined in the context of all the other preferences vary among the federal govern- individual and group act ivity ment ioned

1 above? Can Utah state government really to change, defining the target from informa­ achieve sufficient results to make the effort tion on existing key decision makers and worthwh ile? actions, and formulating a plan for obtaininp. action from the targeted decision makers. A Focus on Flood Problems in Utah I f the current s ituat ion is unsat isfact ory and targeted action can ach ieve sufficienL AlISO state governments take some role change to justify the effort, Utah needs in flood control and floodplain management. a more act ive program for flood cont rol and A few have extens ive programs. Wh ile some floodplain management. Otherwise, state guidance for Utah could be obtained by action cannot be justified. To begin with reviewing the successes and failures of then, who are currently the key decision other state programs (Barkley 1970, Johnson makers whose actions determine flood risk? 1970), Utah's flood hazard situation is so different, in ways explained later, from Roles of the Principal Flood that of most other states that another Control InstItutIons approach was taken for this study. The approach here is to examine the de facto Five principal participants or partici­ flood hazard situation, lives and property at pant groups interact in formulat ing the risk balanced against the benefits from national flood control program in the United floodplain use, in Utah, to search out States. First, large federal agencies problems and appropriace ways for dealing construct reservoirs, levees, and channels in wi th them. a nat ionwide program of structural measures to contain riverine and other major flood Approaches to Flood Hazard Reduction waters. Second, municipal governments construct smaller storage and conveyance The de facto flood hazard situation facilities and generally provide a lesser .result ing from the many independent act ions degree of protect ion against inundat ion directly or indirectly affecting flooding or by local stormwater in urban areas. Third, flood damages is cons idered nonop t ima 1, the federal flood insurance program provides unsatisfactory, or even unacceptable by those floodplain occupants the option to insure who want to eliminate all flood damages or themselves against the financial losses protect all natural floodplain environments caused by flooding but makes the availability on basic principles. This viewpoint is found of the insurance cont ingent on a community in those who advocate floodplain land use f loodpla in management plan as a means of regulations to halt all further building in inducing the communities to pass laws to hazard areas no matter how valid the reason reduce floodplain occupancy. Fourth, the prospective occupant may have for be­ planning and zoning officials in individual coming exposed to the hazard, in environ­ communities enact and enforce regulations to mentalists who would stop all structural reduce new floodplain development and en­ flood control no matter how much benefits courage the flood proofing of exposed struc­ exceed cost or how small the environmental tures. Fifth, but perhaps the most influen­ harm, or in automatic opposition to tradi­ t ial of all on the amount of flood damages t ional structural solutions without giving that occur, individual property managers due consideration to alternatives. It is make the land-use and building-design deci­ also found in those who would automatically sions that determine floodplain occupancy and build all the structural measures needed to make the responses to flood emergencies that achieve full floodplain development. Neither determine resultant losses. In addit ion to extreme is effective. The first ignors major these five, other participants engage in economic losses, and the second ignors flood forecasting; urban, recreation, major environmental harm. or transportation planning; and many other roles that are also important but less A more effect ive approach is for those central to the overall program. who perceive either economic losses or environmental harms to. interact with key The decision makers in these five decision makers (where ever they are in the principal roles vary greatly (both within a total decision process) in order to reduce role and between roles) in the a) range of the frequency or severity of the result ing actions at their disposal, b) area of juris­ problems. As an example relating to this diction, c) criteria or values, and d) time study, Utah is in no position to change horizon. Listed below are the general national policy found to be placing lives or situations, with respect to each of these property at risk unnecessarily or unduly four dimensions, of the decision makers in restricting floodplain use in this state, but each of these five roles. efforts properly targeted to change particu­ lar decis ions or act ions may be very ef fec­ 1. The federal agencies (principally t ive. the Corps of Engineers on the larger rivers and the Soil Conservation Service on smaller In order to be ef fect ive in th is role, upland watersheds) a) implement programs of it is necessary to begin by defining appro­ engineered construct ion, b) have a nat ional priate targeted efforts. The task includes program that draws on a nationwide cadre of identifying aspects of the current situation expert ise in most skills relevant to water which are in the best interest of the state management, c) formulate their designs on the

2 basis of the Water Resources Council Princi­ exposure of property to flood risk is deter­ ples and Standards (1973, 1979) established mined by dynamic interact ion among many through nat ionwide consensus on water plan­ decision makers. Actions by one group ning goals, and d) evaluate feasibility based conflict with actions by another, and dif on 50-year planning periods. ferences are resolved as individuals interacl in prevailing institutional arrangements. 2. Municipal stormwater programs Since the five groups named above act at (generally directed by a municipal engineer) three levels (national, community, and a) implement programs of engineered construc private) and vary greatly in resources, tion that are designed at a much smaller authority, and expertise, the efforts of scale than those of the federal agencies, b) anyone group to reduce the amount of proper­ are active only within their own municipal ty at risk often have unforeseen consequences boundaries and have much more limited access and their effectiveness is very difficult to to planning resources and expert ise, c) predict. Some hints, however, can be found formulate their designs based on applications by exploring the role in more detail. of familiar engineering standards to meet the perceived needs of local citizens under Role Interaction in the Existing Program guidance supplied by leaders in municipal government, and d) evaluate financial as Historical Role Development opposed to economic feasibility and that based on planning periods often tied to The Flood Control Act of 1936 institu­ statutory limitations on the life of munici­ tionalized nationwide federal funding pal bonds and averaging around 20 years. for structural flood control in the United 3. The federal flood insurance program States. The program began with the reser­ a) provides informat ion on flood hazard and voirs and levees built by the U.S. Army Corps uses its program as an inducement to get of Engineers to protect floodplains along local communit ies to reduce development at larger rivers. The Soil Conservation Service hazard, b) is active nationwide and has later became active in developing projects on limited (but increasing) expertise in many of smaller tributaries and in upland areas. The the disciplines relevant to flood control Bureau of Reclamation has included flood planning and technology, c) does not follow control storage in its mult ipurpose reser the Principles and Standards but employs voirs but does not implement single purpose uniform scaling rules based on such physical flood control projects. All three agencies criteria as a lOO-year floodplain or a have active flood control programs in Utah, one-foot allowable floodway backwater, and d) but the programs are less ext ens ive and implements its program based on current individual projects are smaller than in parts conditions with no allowance for increased of the country where a more humid climate risk caused by· future intensification of and greater rainfall intensities cause upstream watershed land use. greater flood problems. 4. Municipal planning and zoning boards The 1936 Act also institutionalized the (normally staffed by people trained as economic efficiency criterion for federal generalists) a) pass and enforce land use water resources planning (James and Rogers regulations, b) are active only within their 1979) by decreeing that federal monies own municipal boundaries and seldom have could only be used to finance structural significant expertise related to flood flood control if benefits, equaling the control technology, c) formulate plans from damage reduction achieved, exceeded costs. criteria that are not explicitly defined but Other rules .prevent the federal effort from generally comply with accepted practice protecting areas where the inundation because within the planning profession and are of long duration, small volume, frequent responsive to pressures from local citizens occurrence, or local source is considered a and state and federal authorities, and d) drainage rather than a flood problem (James generally target on meeting community and Lee 1971, p. 229). Municipal drainage needs over the next 10 t~ 30 years. programs have focused on these localized problems. 5. The managers of individual proper­ ties a) occupy their land and sometimes Over the years, implementation of the construct facilities on it, b) have control federal program for structural flood control only over their own property (though they may proved increasingly costly. What was worse, influence and be influenced by neighbors) and total flood damages nat ionwide cont inued to seldom have expertise in any relevant profes­ increase. The federal response was to s ional discipline, c) respond to vaguely promote floodplain management (Levin 1970). defined individual needs and personal goals Zoning was recommended to keep damage-prone rather than to formal criteria, and d) vary property from high flood risk areas, and greatly in their time frame for analysis bu ilding codes were recommended to require depending, among other ~hings, on whether less damage-prone (flood proofed) construc­ t hey are seek ing inves tment income or a tion when floodplain development occurred. permanent home for themselves and their Under the new flood control policy the ideal children (James 1968). flood control planning mode considered both these nonstructural options along with the As a consequence of these multiple roles structural flood control measures and selec­ and the multiple actors within each role, the ted the optimal mix.

3 Implementat ion of such an integrated under 24 CFR 1910.3 (c) and/or (d) and 24 program is, however, a problem. The con­ CFR 1910.5. Communities with significant stitutional separation of powers gives the flood problems are thus pressured to adopt federal government authority to construct strong management regulations, not because flood control facilities that promote the they really believe them needed, but so that general welfare but leaves to the state and, their ci t izens can obtain the insurance and as delegated by the states, local government thus reduce their expected flood loss. authority for land use planning and regula­ t ions through zoning and building codes. A second goal intervention is found in Consequently, the federal government cannot the direct subsidy to pay the cost of non­ directly implement the nonstructural com­ structural program components. The flood ponents of a flood control program but proofing of existing buildings may be outside rather has to use incentives to encourage the financial capabilities of the owners even s tate and local implementat ion efforts. though analysis shows economic justification State and local governments, on the other by benefits in excess of cost. Partial hand, do not have the finances, or in federal payment of the costs can then al­ some cases the authority, to implement the leviate the shortage of funds. Individuals, structural measures they may consider who make comparisons in terms of out-of­ essent ial for the welfare of their com­ pocket expenditures, will be more likely to munities. Consequently, governments at flood proof. these lower levels frequently use their influence to encourage federal project The federal information dissemination construction. effort has sought to reduce floodplain occupancy by broadcasting the results of State and local efforts to procure hydrologic and hydraulic studies to map flood structural flood control have lessened hazard areas. The program reduces the number with the environmental movement and the of people moving onto the floodplain unaware resulting gain in favor of the nonstructural of danger, but the results have been less approach. Even where local pressures for than successful from the nat ional viewpoint construction continue, the federal agencies because many people are willing to assume are increasingly likely to decline (or greater risk than they should according to indefinitely delay) construction of flood the accepted nat ional viewpoint. McCrory et control structures, and communities with al. (1976) estimate the average annual flood problems are forced more and more to expected damage to a home just outside the turn to the nonstructural measures that they margin of the average 100-year floodplain to can implement. In this mode, the federal be about 0.23 percent of its market value. government encourages local nonstructural They then cite survey results of Atlanta programs, and the local governments seek floodplain residents indicating that the federal acceptance of their nonstructural average person seriously considers moving off efforts as qualifying them for flood in­ the floodplain when experienced average surance. These are just a few examples of annual damage reaches 2.0 percent, and they how the alternative of influencing others is est i ma t e t hat the t h res hoI d val u e for for many more viable than any direct action moving onto a floodplain would be about 1.0 alternative. percent. Disseminated flood risk information is thus not going to disuade people from The Federal Influencing Mode moving onto mapped floodplains where the risk lies in this intermediate range between 0.23 Haimes (1977, p. 63) lists three ways and 1.0 percent. In Utah, the highest risk that higher echelons in a hierarchy can found by Woolley (1946, p. 57) in compiling manipulate choices made at lower levels. 89 years of flood history was about 1 in 15 These are 1) intervention to make local goals or 6.67 percent. Most risks are far lower, conf~rm more closely to national ones, 2) and Utah probably has, because most flooding information dissemination to make local is quite shallow, a larger percentage of its expectations of the outcome of actions in mapped floodplains having risks less than national disfavor seem less attractive or 1.0 percent. In fact shallow flooding those in national favor seem more attractive, suggests less than the average damage rates and 3) constraint intervention to complicate of 0.23 percent. The conclusion must be that or make impossible local implementation of flood hazard information can generally be alternatives in disfavor at higher levels. expected to be less effective in Utah than in The federal flood control program has used most places in reducing floodplain occupancy. all three. One constraint intervention that the One goal intervention is found in the federal program uses to influence local subsidization within the federal flood decision making is a policy to install insurance program of flood insurance for structural measures only when supplemented by buildings that were constructed in the appropriate nonstructural alternatives (Water floodplain before the program began but only Resources Council 1979, p. 30211). Other if the community (city or county for rural constraint interventions are provisions in a reas) has adopted a floodplain management the Flood Disaster Protection Act of 1973 program cert if ied by the Federal Emergency that prevent many lending institutions from Management Agency (FEMA) (formerly by the financing floodplain development in com­ Federal Insurance Agency, FIA) as adequate munities without approved nonstructural

4 program and the provisions of Executive Order federal government in implement ing its flood 11988 (May 24, 1977) which require federal control program lies in this separal ion agencies to avoid floodplain occupancy or between the locus of decision making for act ions that st imulate floodplain occupancy policy formulat ion and the locus of cont rol by others. for implementation of the selected measures. Since states have even less centrol, their State and Local Influencing Modes problem in this regard can be expected to be even greater. The chief ways that lower echelons have to influence h er levels in a hierarchy are Study Objectives to 1) apply or technical or financial assistance, 2) use political influence within The general study objectives are 1) the decision making process, and 3) interact, to identify where the existing flood control either informally or through inst itut ion­ effort in Utah is unsatisfactory from state alized public participation processes, and local viewpoints and 2) to determine what with agency employees charged with program state government might do to improve the administrat ion. All of these avenues are total flood control effort. Specific sub­ frequently used in flood control. Com­ objectives include the following: munities and individuals seek federal assistance of many sorts and use ~heir 1. To ident ify s ituat ions in wh ich the political influence to promote favorable current program is proving unnecessarily responses to their requests. Technical elaborate and costly from the state and local people work ing for communi ties interact viewpoints and suggest courses of action for with counterparts in federal agencies, and the state that would help reduce the program individuals with special problems often bring to become more in tune with local needs. these to the attention of government of­ f icials. 2. To ident ify situat ions in which the current program is not providing adequate Guidelines for Formulating protection from flood hazard from the state a State Program and local viewpoints and suggest courses of act ion for the state that would effect ively The need for Utah to become more active expand the program to meet these needs. with respect to flood control is strongly related to the fact that national decision 3. To recommend any further stud ies making biases the federal program toward needed to refine our understanding of needs in average flood hazard s ituat ions s ituat ions and alternat ives in order to whereas Utah s ituat ions are not typical of proceed with the above determinations. others nat ionwide. The problems caused by this difference in physical context, as well Study Organization as by any differences in goals, are ac­ centuated by the lack of resources in local The organizat ion of the mater ial to government to formulate well-structured follow begins in Chapter I I by present ing a policies and negotiate differences with the framework for understanding the dynamically federal government on anything like an equal interactive feedback processes through which basis. people seek benefits from floodplain oc­ cupancy, exper ience sequences of flood If Utah is to become more active, the events, and respond by modifying their oc­ effort should focus on targets where it will cupancy or the pattern of flooding. Through be cost effective. Specific recommendations these processes, society balances benefits for formulating a targeted state actlon against risks. Efforts made by government to program require a standard that can be used alter this balance generate additional im­ to assess the effectiveness of proposed pacts, some beneficial and others detri­ act ions. The standard should ideally be mental. The result is a foundation for use defined xhrough a political process in which in deciding how to weigh the de facto balance value judgments balance pros with cons while between benef its and risk and governmental interacting to a consensus. The standards efforts to change this balance from the Utah used to formulate structural flood control perspective. projects and the rules used to manage the flood insurance program have resulted from The study then proceeds to describe the these sorts of interactions at the federal existing situation in Utah. Chapter III sum­ level. This study to define a state role marizes empirical data on flood risk. needs to consider the differences in the Chapter IV examines the decisions being made standard one could expect from a Utah con­ at the national, local, and individual levels sensus. to reduce the hazards of floodplain oc cupancy. Chapter V surveys situations in The federal flood control program was selected Utah communities. Chapter VI probes formulated from a national viewpoint and yet selected situations in greater detail to try requires cooperative implementation at levels to find caUSes for the ident if ied problems. from the federal government, through state The final chapter analyzes the informat ion and local jurisdictions, to individuals presented in the earlier chapters through the making their own floodplain occupancy deci­ framework of Chapter II to identify needs for s ions. The fundamental problem for the program improvement.

5 CHAPTER II

A CONCEPTUAL FRAMEWORK FOR DEFINING A STATE PROGRAM

Introduction differe~ces can be amplified by a dynamic lnteract lve feedback process. Finally, the The policy objectives for flood control current state flood control program is or any other program area in a democratic described and used with the above background society should express public preferences. as a foundation to suggest promising direc­ Formal processes to set objectives should t ions for improvement if supported by needs provide concerned citizens opportunity to revealed in the empirical descriptive data express their preferences and lead to an to follow. unbiased resolution of revealed differences. Actual consensus-seeking processes fall short Components of the Conceptual Framework of this ideal; and, more important for the purposes here, political consensus making is Initial Conditions only capable of setting public policy with respect to a few topics simultaneously. This At any given time in any given flood­ means that the issues with respect to a given plain, some state of occupancy and hazard program area must reach a certain level to that occupancy exists. The occupancy can of salience before they surface politically. be defined in terms of the physical use and Flood problems in Utah have not been suf environmental state of the floodplain. The ficiently salient for this to occur. occupancy provides some amount of economic gain (or loss) to the occupants and also This historical lack of political provides certain social satisfaction (or salience means that flood problems in Utah dissatisfaction) not easily translatable into are handled administratively rather than economic values. Very severe events pose politically. Action in the executive branch some risk of cultural or governmental change of state government is important because that create uncertainty and may substantially floods can bring disaster, flood programs add to the loss. The occupants hold some mix formulated at other levels can have important of cultural values and are ruled by some adverse consequences for the state, and it is hierarchy of governments. The hazard can be in the public interest for government to act defined by integrating these occupancy to remedy incipient problems. Action re­ conditions with the hydrologic risk and quires identifying inCipient problems and expressed in terms of expected (in the moving to prevent them from magnifying. probabilistic sense) average annual economic Specifically, it is in the interest of the loss. Added dimensions can be specified in people of Utah to prevent excessive flood terms of expected environmental or social damages or dissatisfaction with a national loss. flood control policy from increasing to the point of becoming an important statewide The Stimulus political concern. At any point in time, a flood may. occur, Decisions throughout both the public a new reservoir may be built, extensive new and private sectors interact ively determine urban development may occur upstream, a floodplain land use, flood hazard, urban strict floodplain zoning law may be passed, growth patterns, etc. It is these decisions an individual may flood proof his house, or a ~hat could, if unwatched, generate political state flood control planning program may be lssues ln Utah. The decisions that are inaugurated. All such stimuli can potential­ being made need to be examined with respect ly change the floodplain conditions. The to their potential for leading to future change may follow the action or precede problems, and the interact ive processes it as people anticipate the action in ad­ generat lng the problem dec is ions need to vance. As an example of the latter, people be examined in order to define alternative begin to react to plans to build reservoirs approaches for counteracting them. long before those plans culminate in con­ struction. For this study, the establishment This chapter begins by presenting a con­ of an expanded state flood control planning ceptual framework for understanding the program is the stimulus to be examined. lmpact of flood events on a local community and the responses made at var ious levels to Consequences those impacts. The analysis goes on to examlne the reasons for differences among The consequences of the stimulus may be the various groups working to solve flood defined as the changes that it causes to the problems at different levels and how those initial conditions. All changes are theo-

7 retica11y relevant; but for practical evalua­ and the United Nations. Each higher level tion, one must define a lower threshold below (e.g., state) is an aggregation of lower wh ich consequences will not be noted. The level units (e.g., counties). consequences may be conveniently classified along the five dimensions of Figure 1 (Larson The consequences which are first experi­ el al. 1979). In each dimension, the con­ enced at the lowest level of the individual sequences or impacts are first experienced by person aggregate to be experienced at the individuals who find that the stimulated next higher level provided that the aggregate changes have past their detection threshold. effect passes the detection threshold of the More severe st imulations cause consequences higher level. As shown on Figure 1, effects that pass the thresholds of larger groups. on individuals can potentially aggregate to effects on household groups, and on to larger groups with the highest level effects being of national or international s ficance. Society functions (whether informally or through formal organizations) at many levels. Dimensions of Impact For example, the functions of government are exercised at levels from small communities or Five impact d imens ions are shown on special districts up to national governments Figure 1. Impacts in the physical-environ-

Figure 1. Impact dimensions of an implemented action.

8 mental dimension begin at the first level price or availability of goods and alters with changes in suitability of small areas his decisions to buy or sell accordingly. for given uses because of changes in land forms (e.g., through construction), flood At the first level, a locus of decision hazard, or natural environment. Changes in making exists for every individual. He makes small areas alter overall use of a lot by an decisions in all five dimensions; each individual. As many lots are affected, decision is influenced by consequences consequences aggregate (through hydrologic, perceived in all five dimensions. As ex­ ecologic, meteorologic, and other linkages) amples of dec is ions in the five d imens ions, to affect subwatersheds and eventually larger the individual may alter his use of the land, areas. buy or sell different items for different amounts, modify his pattern of behavior, A given stimulus turns out to be both interact differently with others in order necessary and sufficient to produce certain to achieve personal or group goals, and impacts and a contributory cause to many communicate new desires by contacting key more, and the degree of contribution general­ individuals in various levels of government. ly lessens at progressively higher levels. Obviously, decisions made in one dimension As the degree of contribution decreases, the affect those made later in others, and this difficulty increases in assigning or blaming is the reason for showing all five in Figure an impact to a considered or implemented 1. For example, cultural change can have a action for planning or monitoring purposes. major impact on the success of federal nonstructural flood control programs. Impacts in the economic dimension begin at the first level as the stimulus causes At the first level of decision making, consumers monetary loss or gain by causing individuals responding to larger stimuli can them to buy (e.g., supplies for flood proof­ number in the millions. At higher levels, ing), sell (e.g., property at hazard), or the loci are fewer, the actors part icipat ing I ive in a lower state of sat is fact ion. The in the decision making at a given locus are buying and selling affect firms supplying more, and the decision making process is more or purchasing the goods. Effects at a higher formal. Decisions are influenced by actions level are the sum of those experienced by taken at lower levels and constrained by component lower level units. rules made at higher levels. The actors participating in group decision making at a In the cultural dimens ion, individuals given higher locus vary greatly in the amount change their perception of good behavior as of effort directed to collecting and ana­ they observe events In nature and the actions lyzing relevant informat ion either directly of others. As the stimuli are greater, more or by using technical staff, thought given frequent, or affect more people, additively before taking a position, goals, previous and interactively, changing attitudes change alliances, depth of conviction, and influ­ beliefs, values, and eventually cultural ence. The decisions of the group are deter­ norms. mined by the individual pOSitions and the interactions among the actors. Each decided Socially, stimuli alter individual action (and many expectations of probable satisfactions with the quality of life action) becomes a new stimulus and generates and cause life adjustments other than those new impacts in the five dimensions. expressed as consumers make marketplace decisions. Changes in life quality experi One message of this paradigm is that enced by individuals aggregate as changes for the decisions which determine floodplain families, small social groups, communities, occupancy and the hazard to that occupancy and eventually to society as a whole. are not all made at the federal level in the governmental dimension. That is probably the In the fifth and final dimens ion, indi­ most influential single locus, but it is far viduals may change the ways they govern their from the only one. Since it is but one of own lives. The next level of government many decision making loci, the effectiveness may be thought of as the household where of the federal program is largely determined decisions are made on conduct for family by how well it complements and how much it members. Household decisions, whether by conflicts with the decisions being made at voting or interaction with public officials, all the other loci. can influence the rules used to govern communities; and these interact to change Alternatives rules at higher levels all the way up to the nat ional. Decisions are made among alternative courses of action in order to change existing cond i t ions or r educe changes that would Loci of Decision Making otherwise occur. The alternatives may either be options which can be exercised directly at Each impact node (level along a dimen­ the locus of decis ion mak ing or desires for s ion) is also a locus of decision making for action at some other locus. In the first reacting to the impact. A consumer, for case the decision maker follows through to example, does not ignore the effects of the implement his decision, while in the second stimulus on the markets in which he buys and case he tries to influence others. As sells but rather evaluates any changes in the examples of the latter, individuals express

9 desires for action they would like to see welfare economics to evaluate alternatives taken at higher levels, and higher level loci through the framework of benefit-cost analy­ generally expect lower levels to comply with s is (James and Lee 1971) or mult iple objec their choices. In either direction, the t ive planning (Haimes 1977). According to alternative courses of action become alter­ the framework of the Principles and Standards native means of exercising influence on other (Water Resources Council 1973, 1979), values decision levels. The higher the level of a are expressed as basic principles, and all decision locus, the more it will have to rely the rules in the standards and procedures and on exercising influence rather than direct their interpretations in program administra­ implementation. Governmental nonstructural t ion are the guidance system. The environ­ flood control programs are essentially mental impact statements required by the efforts to influence lower level decision National Environmental Policy Act of 1969 are making, and the alternative courses of action supplemental guidance information. are alternative means of exercising that influence (James 1975). These guidance systems need to be considered as they relate to the five Relevant Information impact dimensions of Figure 1. Decision making at a locus associated with each impact The information relevant to deciding dimension, as shown in Figure 2, emphasizes a among alternat ive courses of act ion is that different feasibility question and optimiza­ describing differences among the consequences tion goal. In the physical-environmental they st imulate. Informat ion on s ituat ions d imens ion, the feas ibility assessment deter­ that would be the same no matter which mines whether it is physically or environ­ alternative is chosen is irrelevant. To mentally (biologically) possible for the be practical, small differences must be action to achieve the desired results. Many ignored, and relevance is defined in terms of would separate physical or engineering a difference large enough to matter to the consequences from environmental or ecological decision maker. Some individuals are more consequences, make an economic appraisal of sensitive to differences in one dimension the first, and consider the second as a (e.g., economic) while other individuals are constraint. The purpose here is not to more sensitive to differences in other advocate either approach but rather to note dimensions (e.g., cultural). Decision makers that actions generate consequences which can vary in their threshold of what matters. be predicted (with varying degrees of cer­ Consequently, information that seems relevant tainty) and that the nature of those con­ to one seems irrelevant to others. sequences determines whether the desired results are possible. The probability of Guidance for Decision Making achievement is essentially a scientific determination. One example of optimization in Decision making processes vary all the this dimension alone would be a determination way from instantaneous snap judgments made by to add irrigation water until maximizing crop individuals unaware of many of their alter­ yield. nat ives and un informed or mis informed as to the consequences of the actions they select, Commonly used guidance systems also to, at the other extreme, a long, carefully cons ider the economic d imens ion of whether considered process of defining alternatives, the act ion will pay (from the viewpoint of eliminating infeasible ones, and choosing the decision locus). A more limited view of from among the opt imal and near opt imal this general question of economic feasibility through interactions within a collective body is the question of will it pay in ways that of decision makers. While the magnitude of will monetarily recompense those who pay the the effort does not alone determine the wis­ bills. Optimization in this dimension is to dom of the decision, decision making is gen­ maximize net benefit (or net revenue from erally improved by accurate information on the more limited financial perspective). One relevant points and sound analytic proce­ would stop applying irrigation water when the dures. value of the increased crop yield no longer exceeds the cost of the water. The most commonly used guidance system at the higher levels in the private sector is Guidance procedures commonly used for the engineering economy study. Public sector flood control planning explore legal feasi­ water resources planning adds inputs from bility in the governmental dimension but do

Dimension Feasibility Question Optimization Goal Physical-Environmental Is it possible? Maximize production Economic Will it pay? Maximize net benefits Social Is it wanted? Maximize net satisfaction Cultural Is it allowed? Minimize conflict Governmental Is it legal? Maximize public welfare Hough, Granville W., "Technology Diffusion," Mt. Airy, Md.: Lomond Books, 1975, p. 33, 406 p.

Figure 2. Feasibility issues by impact dimension.

10 very little with the social and cultural information to use in decision making may be feasibility questions and optimization goals called a percept ion filter. The filter is shown in Figure 2. This very fact may cause seldom a congcious selection of which iden­ considerable difficulty in coordinating tified facts to use but rather the outcome of federal plans with the actions of individuals accumulated experience with facts ignored because decision makers using informal without ill effects. guidance procedures are likely to concentrate their attention on these dimensions. Any Operat ionally, each actor only uses state flood control effort should carefully information that he perceives relevant establish a suitable. guidance procedure to achieving his goals, considering the and modify it as applications suggest pro­ capabili ties and resources he has ava ilable mising improvements. An arbitrarily gUided (Bates 1965). The filtered-down guidance state effort is highly unlikely to be pro­ system, called a perspective by Moline (1968, ductive. p. 95), 1) limits the operational goals used to ones the decision maker feels comfortable Differences Among Decision Loci in pursuing, 2) operationalizes specific evaluative criteria to pursue those goals, 3) Limitations in Use of Guidance regards information outside the scope of those evaluative criteria as irrelevant, No decision making locus uses a compre­ 4) biases interpretation of incoming informa­ hensive and fully objective guidance pro­ t ion in favor of the defined goals and cedure. Much relevant informat ion is never favored alternatives for achieving them, and obtained because it is too time consuming or 5) leads toward alliances with others of com­ costly to collect. Information storage and mon perspective. Each actor is relatively retrieval systems are not capable of deliver­ open to external inputs when he is inexperi­ ing all useful data expressed in under­ enced in a given area of decision making and, standable terms for every decision making over time, filters out increasingly more need. Many consequences of the alternat ives information. Only an experience of ill being cons idered cannot be cred ibly pre­ effects because key facts were ignored is d icted, in large part because of the change likely to reverse the trend and broaden one's that exogenous events and decisions made at perspective. other loci cause in the situation context over a period of analysis. Explicit tech­ I t is thus the adopted perspect iVe, not niques are not available for dealing with the relevance as defined objectively, that deter­ diminishing causality attributable to mines what is considered or not considered by an initial effect with the passage of time a given actor at a given locus of decision (Larson et a1. 1979). Finally, forecast making. Consequently, different actors, who consequences cannot be fully expressed in have different experience histories, adopt terms of gains and losses within the frame­ different perspectives and come to conflict­ work of a generally accepted value system, ing decisions among the alternatives. and conflicting value preferences cannot be reasoned to an objective conclusion. It is the perspect ive of actors at the federal level on the governmental d imens ion In addition to these technical limita­ of decision making that filters the informa­ t ions to the current state of the guidance tion used in formulating federal flood art, 1 imi tat ions wh ich can be overcome by control policy. I t is the perspect ive of a technological and analytic advances, a more local government that sets community policy fundamental problem is found in the fact that on floodplain management. It is the perspec­ people feel more comfortable with decisions tive of an individual that determines his tempered with human judgment. The very reactions to the federal and community the suggestion of a comprehensive and objec­ programs. Obviously, the perspect ives are t ive mechanical guidance system to replace going to differ among these levels and among human decision making scares people. We fear loci (communities or individuals) within a a mechanical optimality devoid of truly human given level. Assuming that Dtah is not values, a dictator that will make us do what interested in the direct implementation of a is "best" whether we like it or not, and the structural flood control program, a state possibility that someone will remold the flood control program can only reduce flood system for personal gain. damages by changing perspect ives so that decision making by others changes flood­ Resource management dec is ion mak ing is plain occupancy decisions or flood hazard expected to combine objective analysis with situations. subjective evaluation of intangible con­ siderations. The practical factor controlling Differences in Information Used the combination of the two is that the amount of Information which can be obtained through The total body of information relevant objective guidance procedures overloads human in that it describes differences among decision making. Consequently, human decision alternatives may be represented by the shaded makers select wh ich gu idance they will use area in Figure 3. When decision makers A and and which they will ignore. B choose among the alternat ives, they a) do not perceive all of the differences, b) The process used to select how much of perceive some consequences as different which the total body of available or obtainable in fact will not be, and c) vary in the

11 .. :.::::: ::~:~:~: ~:~: ~:~!;: :=: :::::: ... ~ ·::::~H)~:~~·~i··B~·d~·~f·~~~~n~~H~;~~H~~:::: .. • ::::::: ...... *~ ••• ~:.:.:.:.:.:.:.:.:.: • . ,::::::::::: Re levan! ,'~~onn.a!l.o.n,:::::::::::::::::::::::

Summary of Six Information Types 1. Relevant information not per­ ceived from either perspective 2. Relevant information perceived from both perspectives 3. Relevant information perceived from only one perspective ! ...... :.~:::::::.:.:.:.:...... 6 4. Information that is not rele­ vant even though it is perceiv­ ed so from both perspectives \ : 4 / 5 ...- 5. Information that is not rele­ 5 ' / ' vant even though it is perceiv­ ed so from one of the perspec­ ,,~/ tives .Information t ...... \ •.,..../ •••• ,' '/J 6. Information that is not rele­ Perceived by B ' ., •• ,' Information vant and is not perceived rele­ Perceived by A vant from either perspective

Figure 3. Conceptualization of overlapping information sets.

differences they perceive. The difference implementation alternatives of adding to the in perception filters between the two leads area or working with Type 3 information that to differences in the information considered pertains to most of the decision makers. One relevant and to classification of the six potential state role is to make sure that information types shown on Figure 3. federal implementat ion efforts do not con­ flict with state interests. Several appl icat ions of Figure 3 apply 3. Type 3 information is relevant and to the floodplain management problem: perceived by some but not all of the decision makers. Many times, only a few floodplain 1. Type 1 information implies decisions users disregard floodplain management pro­ made in ignorance of their consequences. A grams. If the Type 3 information they large body of Type 1 information suggests perce ive can be ident if ied, changing these an opportunity for state government to obtain this information and disseminate it to the consequences or perceptions of them, particu­ decision makers so that they are less likely larly when it can be done economically, to be caught unawares. may be the most cost effective implementation method. 2. Type 2 informat ion is relevant and 4. Type 4 information relates to perceived by all decision makers. Any consequences perceived by all decision floodplain management program must in order makers as varying among alternatives even to alter floodplain use decisions do one of though it really does not. Operationally, a) add to the Type 2 area (distribute floodplain management programs could supple­ flood hazard information), b) change con­ ment or alter Type 4 as well as Type 2 sequences in the Type 2 area (impose fines on information, but ethically one should ques­ nonconforming land uses), or c) change t ion efforts to influence others by dis­ perceptions of those consequences (create an seminating false information. Type 4 infor­ atmosphere of social nonacceptability). For mation works to bias floodplain land use the many property managers on a real flood­ decisions and consequently suggests a pos­ plain, the Type 2 information, that is sibly important state role of disseminating perceived by all of them, is likely to be correct informat ion to reduce these mis­ quite small. This situation leaves the conceptions.

12 5. Type 5 informat ion is perceived as the degree to which it has the power to varying by some decision makers even though implement that its plans. At the federal it does not. Better floodplain land use is level, the cens t ruct ion agencies have proven furthered by eliminating these misconceptions power to construct and maintain structural as well. measures as designed. The insurance program does not yet have a proven track record of 6. Type 6 information does not pertain achieving sustained successful community to the declsions at hand and no one thinks floodplain management programs and is con­ that it does; however, one cont inually finds s iderably disadvantaged by the fact that a great deal of space in government reports instead of being able to implement with its on flood control alternat ives and environ­ own forces, as do the structural agencies, it mental impact statements in particular taken must influence each community to influence by Type 6 information. Every effort should its citizens. An indirect implementation be made to direct studies toward more produc­ process is always far less controlled tive information gathering. than IS a direct one. With respect to function, the structural agencies have 7. One of the many units involved in a long been weak in capabilities related to flood control program is the state itself. land use management but have recently If the state is to have an effective program, made significant staff expansions to remedy effort needs to be made to expand state this deficiency. FEMA has suffered from perception of relevant information and reduce weakness in hydrologic and engineering state-perceived consequence differences that capabilities. Communities vary greatly in do not exist. strength and weakness of functional expertise and are as a rule weaker in technical areas Elements of Perspective than are their federal counterparts. As is the case for the federal government, Since floodplain management program community expertise is normally divided implementation is made more effective between engineering departments responsible by better understanding of how decision for structural measures and planning depart­ makers vary in the information they consider ments responsible for nonstructural programs. relevant to floodplain use decisions, a At the individual level, functional expertise taxonomy for defining how perspect ives vary and financial resources are very limited, a can be very useful. Larson et al. (1979) lack that causes many actions to be taken define perspective in terms of four elements: which later fail to function as intended range of act ions, scope of control (jur is­ (physically-environmentally infeasible). As diction), favored values, and time frame. one goes to higher levels (Figure 1), one The summary descr ipt ions of these elements finds the principal feasibility constraints for the five principal participants noted in to tend to move from technical and financial Chapter I in the Nat ional Flood Cont rol to social and cultural. As to the geographi­ Program can at this point be cons idered in cal aspect of scope of control, the higher greater depth. levels serve larger areas and find themselves constrained by pressures for uniform policy The range-of-action element is estab- to treat all areas equally despite variations 1 ished by the act ions that those holding a in local needs. The lower levels ident ify perspective have the power to implement. At with the specifics of a particular local the federal level, structural agencies can situation. provide or withhold structural measures or technical or financial resources to supple­ The favored-value element describes the ment certain local nonstructural activity. objectives pursued. The federal agencies The Federal Emergency Management Agency responsible for structural flood control (FEMA) can use incentives to promote com­ follow the Principles and Standards of the munity flood control programs. Communities Water Resources Council (WRC 1973, 1979). can implement local structural flood control The Federal Emergency Management Agency is programs and employ floodplain zoning and one of two agencies with major water re regulation of building practices. Decision sources management programs (the other being makers at the individual level vary in the Environmental Protection Agency) that perception from those who see themselves does not use the Principles and Standards. entirely at the mercy of flood disasters to The program is managed to promote floodplain those with faith in their ability to plan management the country and make flood in­ their land use and construction practices so surance available to all who want it and does as to go relat ively unharmed no matter what not require feasibility analysis to determine floods occur (James et al. 1971). Decision their appropriateness in specific floodplain makers at all levels only employ actions s i tuat ions. State and loca 1 goals are not within their range. Consequently, each is explicitly defined, tend to be somewhat more interested in informat ion that affects volatile as leadership changes through the the performance of act ions with in h is range political process, and are generally oriented than in information that primarily relates to toward the needs of the local people. other sorts of action. Individual goals vary Widely from person to person and change over time. Many value The scope-of-control element defines the confl icts are found at lower levels but are geographical area in which a group can act, resolved at the higher levels as actors give the extent of its funct ional expert ise, and and take in group decision making. Neverthe-

13 less, value conflicts become an extremely identify tbeir sources as a first step in important obstacle to implementation of a correcting the situation. If this is done, cooperative program such as floodplain most conflict£ can be identified with dif­ management. The program was def ined by ferences in perspective among decision national values and then is to be implemented makers. The four elements of perspective at state, local, and individual levels, where thus provide a convenient taxonomy for those bolding different values are inclined understanding the conflicts. As shown to occupancy decisions that conflict with on Figure 4 (Larson et al. 1979) and de­ preferences determined by planning at the scribed most extensively by those authors, nat ional level. Some compensat ing incent ive one obtains a suggestive list of conflict IS needed to bring the local actions in line, sources that can be examined more tborou~hly and development of effect ive incent ives is when specific conflicts are identified. the one key to successful federal programs. For example, identified conflicts between federal flood control programs and desired The time frame element of perspective state ograms may become attributable to has become standardized at 50 years for specif sources, and knowing which ones can planning federal structural flood control be helpful in resolving the conflict. measures and has not been defined but is implied to be quite long for the federal nonstructural program. Lower levels of Decision Dynamics decision making generally plan toward some­ what shorter time horizons, and this dif­ iew ference in time frame complicates recon ciliation of differences in values. The immediate impacts of a st imulus change witb time as the stimulating force Classification of Conflict Sources moves from a prediction, to an experience, to a continu situation. They wax and wane as The decisions affecting floodplain oc­ the stimu ation intensifies or withdraws. cupancy and bazard being made at the many It then takes time for the impacts to aggre­ loci often conflict or lead to efforts that gate from lower to higher levels where .influence others in conflicting directions. perceptions of them are delayed and averaged When such conflicts occur, one needs to over time.

Temporal Values Jurisdic tion Actions

Different horizons Short run vs. long Changing boundaries Sequencing of actions Conflicts in run goals Creation and termina- Implementation time sequencing Value changes tion of agencies lags coordination Salient and Changes in authority Technological satiation cycles Changes in staffing Time lags in value expertise aggregation Changes in financial resources Temporal Polarities and Agg"fegative and Criteria of achieve- affinities distributive ment Different orderings effects "Accidental" Aggregation Assignment of appro- conflicts Acceptability of priate functions conflict Local interest Values resolutions variations Aggregation Coordination Integration Duplication Externalities Capacity and Duplication and utilization overlap Thresholds Creation and termina- tion of agencies Jurisdiction Area vs. function Exclusivity Specialization Unintended Actions consequences

Figure 4. Conflict types associated with various differences in elements of perception.

14 The impacts from one stimulus can never spend money to rect ify phys ical or env i ron­ be separated from those of many others mental changes (economic dimension), suffer because exogenous events don't wait for an loss which cann~t be evaluated monetarily impact to stabilize. They continue to occur. (social dimension), experience dissonance The reactive decisions at a given locus when reflecting how their own past actions or change not only in response to fuller under­ behavioral patterns have contributed to the standing of the impacts of past actions, but loss (cultural dimension), and resolve to also as exogenous events cause new impacts. change their behavior to make themselves less In many cases the decision maker does not vulnerable in the future (governmental even try to sort out the various causes of dimension). The physical-environmental the situation before reacting. impacts may be caused directly by inundat ion by the flood water or indirectly through Some impacts perceived at a decision flood-caused disruptions to communication or making locus are considered favorable, and transportation facilities, market place decisions are made to reinforce perceived transactions, etc. In numbers increasing causes of their happening. Other impacts are with the size of the flood, individuals considered undesirable, and decisions are exper ience some or all of these kinds of made to counter their causes. impacts, and the experiences of no two individuals are identical. As time goes by, an impact must be credited less to its fIrst cause (e.g., dam The first level impacts aggregate construction) and more to subsequent re­ as the individuals who compose a given second Inforcing actions (e.g., maintenance and level unit share their experiences and work operat ing pol icy). Thus when one project s to overcome common problems (or potent ially impacts over 50 years for est imat ing bene­ dispute over what should be done, even to the f its, he is mixing certain consequences with point of causing a rearrangement of unit other consequences to which the initial membership) .. Anyone individual belongs to a action is a contributing cause; and there are number of !;iecond level units. For example, no generally accepted rules for determining if the flood forces closure of a place of when a level of contribution has dropped to a employment, an individual may share at the po int where it should no longer be counted. second level in the physical dimension with One can say, however, that a longer time lag his fellow workers, in the economic dimension from the c a use tot he e f f e c t red u c est h e with his family, in the social dimension with probable degree of contribution. This is his friends, in the cultural dimension only another way of saying that pred ict ions through his church, and in the governmental become more uncertain as they are extended dimension through his community. In some further into the future. dimensions, an individual may be a member of more than one second level unit (e.g., he may As time passes, the above continuous, have more than one circle of friends). dynamic interact ions in mult iple feedback loops (Forrester 1961) change the current The aggregation process at the second state of floodplain occupancy and hazard to level in a given dimension sums the impacts some other state. Any representation of this in that same dimension experienced by members process must cons ider not only the feedback of first level units. The aggregation is dynamics within the process but also such affected by information on impacts suffered external actions or changes as those in by other units and by members of the unit nature (e.g., major floods), cultural norms, in other dimensions. Similar aggregation social values, nat ional economic and fiscal processes occur as one goes from the second policy, federal programs in areas other than to the th ird level and upward to the higher flood control, etc. Knight (1971) attempted levels. to model water quality dynamic(> with such a feedback system, but no one has attempted The aggregation from a lower to a higher holistic modeling of the dynamics of flood­ level in a given dimension may be linearly plain occupancy even though considerable additive or nonlinear in either the expanding basic data have been collected and used in or the damping direction. For illustration specialized modeling (Kates 1962, Doehring in the economic dimension, the total loss to and Smith 1978, Andrews et al. 1978, Hopkins a consumption unit (the second level unit et al. 1976, Morin and Shin 1977). defined in the economic dimension on Figure 1) may simply be the sum of the losses to Flood Impacts unit members. If the total membership of the consumption unit (perhaps all the wage Flooding inflicts adverse impacts in the earners In the family) do not have the five dimensions of Figure 1. Events are financial resources to cope with the loss or large enough to be a problem when they the market cannot supply the need (Yancey et are detected in any of these dimensions. An al. 1976), they may seek help from other event is first experienced at the lowest or units, often at a higher level, and the first level as individuals find the physical aggregation process is an expanding one. If and environmental characteristics of their the losses are small enough such that the property or of areas in which they engage in members of the unit are through sharing able various activities changed (physical-environ­ to bear them, the aggregation process is mental dimension), suffer monetary loss or a damping one.

15 The expectation would be for the aggre­ seeks to maximize national economic develop­ gal ion to be expanding where most of the ment and environmenLal quality objecLives lower level units experience major impact within the constraint that project benefits because Loo few of the others within the must exceed costs (Water Resources Council higher level unit would have excess capacity 1973, 1979). Economic goals are national or resources to help. Since each higher level in that benefits are only counted if they are of aggregation has more first level units in not offset by losses elsewhere in the nation, its total membership, eventually the process and environmental goal~are set in large part will bringing in units not affected by the by a national environmental perspective. flood; and at this level, the aggregation Project economic benef its do not have to be will begin to become damping. At still perce ived nat ionally; they only have to be higher levels, the damping may be sufficient shown to exist nationally through a formal for the flood not to have even been noticed. evaluation procedure. Afterwards, the It is this damping capacity that protects impacts of the alternatives In the other society .as a whole from the periodic shocks dimensions are discussed in a public partici­ devastating to subgroups within it. pation process. Finally the formulated projects, if acceptable, are authorized and It is also important to note that flood the money appropriated by the national event impacts are more likely to aggregate to congress. the higher levels before damping out in some dimensions than in others. A flood is more From a SLate perspective, a different likely to come to the attention of federal project may be preferred because 1) economic officials in the governmental dimension than optimization from the national viewpoint iL is to affect cultural norms. differs from economic opt imizat ion from the state viewpoint insofar as costs are paid by One goal in describing the impacts of out-of-state taxpayers or project con­ ULah floods through the empirical data in the sequences occur out-of-state, 2) the environ­ chapters to follow is to observe the level of mental values of Utahns differ from national aggregation at which various magniLudes of norms, or 3) impacts in the other four losses are being absorbed in the various dimensions are viewed differently by the dimensions. As example questions of inter­ people of the state than they are by the est, how frequently do floods occur in Utah? people of the nation. What sizes of floods occur? How large an area is affected by a given flood? What The federal flood control program has likelihood exists for several major floods the potential for significant impacts occurring simultaneously over the state? At in the physical-environmental dimension as what levels have the flood impacts of recent projects are built, in the economic dimension years been absorbed in the various dimen­ as construction money is brought into the sions? What chance is there of larger floods state and, with new federal cost sharing in the near future creating larger impacts requirements, taxes are increased, and in the that extend to higher levels in the various social dimension as families are displaced. dimensions? Cultural impacts grow out of public favor or disfavor for the program because of flood Flood Control Program Impacts damages reduced, envi.ronmental impacts, tax payments required, etc. As outlined in Chapter I, the five principal participant groups In the Utah Municipal stormwater programs. Even flood control program are 1) the federal though the technical design and management of construction agencies, 2) municipal storm­ municipal stormwater drainage systems are water control programs, 3) the federal flood responsibilities of local government, designs insurance program, 4) municipal planning and management pract ices are biased toward efforts, and 5) individual property manage­ the national, as opposed to the state, ment decisions. Decision making units within viewpoint, by national technical standards. each of these groups respond to percept ions A more important problem, however, exists in of flood impacts in ways that generate the smaller design floods used for stormwater impacts in all five dimensions. From the drainage as opposed to flood control design. state viewpoint, both the flood and response Drainage systems designed to contain the impacts need to be watched, lest either lead lO-year flood also collect water during to undesirable situations from the state larger storms and may actually make condi­ perspective. The perceptions (Figure 3) that tions worse during the lOO-year event. guide responses to flood probl~s are impor­ Another problem from the state perspective is L ant because of the clues they provide for that community drainage systems may not be L arget ing state act ions. A general rev iew of coordinated at community boundaries. Moni­ the perceptions and how they guide the toring the design and management of contigu­ responses thus provides background important ous systems may be very important for overall for interpreting the empirical data of the workability during both ordinary storms and following chapters on the de facto flood such large events as the lOO-year flood. program and hazard situations in selected Another monitoring consideration is thaL the ULah communities. act ions of one community may also impact other communities in ways they don't like in Federal construction agencies. The dimensions other than the floodwater aspect federaT flood control constructIOn program of the physical-environmental dimension.

16 Federal flood insurance. The federal Utahns are employing and the nature and flood insurance program, like the federal magnitude of the resulting external effects. construction program, imposes national choices. Furthermore, the potent ial for Anot.her possible scenario is that conflict is greater because the communities individual development or property management are required to enforce the nonstructural decisions may be consider·ed undesirable measures. Some communities may perceive because of their environmental impacts, their loss in not being able to develop a contribution to urban congestion, or other floodplain where the hazard is relatively reasons weakly if at all related to flood low as far greater than any flood damage problems. In some such cases, floodplain reduction benefits gained. They may also management laws may become the veh icle for experience greater difficulty in influencing achieving some other community development FEMA to modify their requirements to match goal. For example, threatened increases in local needs than they do when dealing with downstream runoff have been used as arguments the construction agencies. Culturally, against new urban development by those who Utahns are quite willing to resist perceived prefer the aesthetics of a natural watershed. unreasonable federal regulation. This motive raises other equity and judicial issues. Municital planning.. Municipal l?lanning is gu Idedy some comlnnat Ion of sCIentIfIc Foundations for a Utah Perspective explanations of the consequences of certain act ions, nat ional norms on acceptable com­ Current State Program munity designs, and preferences of the residents of the municipality. The plans The foundations for a future state flood impact a number of people in the economic control program for Utah lie in the program dimension (Vault 1975) and possibly in the that already exists. The Utah Department of social dimension adversely. Others gain. Agriculture has been legislatively designated The resulting conflicts raise questions in (Laws of Utah 1979) as the state agency the cultural dimension as to the equity of responsible for coordinating structural flood the community forcing citizens to suffer control programs. This involves working with uncompensated losses, and some of these the So il Conservat ion Servi ce. The governor may require judicial resolution in the by executive order has designated the Divi­ governmental dimension. Since few municipal sion of Water Resources as the state agency planning groups have much expertise in flood with coordination responsibility with respect related technology, the state may have an to the National Flood Insurance Program. important role in providing technical support or in monitoring planning decisions for The state floodplain management effort probable adverse impacts on flood problems. began in Utah, as in most other states, in response to a Federal Insurance Agency Indivi~ll

17 2) enact necessary land use prevent flood problems from enterIng Lhe regulation enabling authority polil ical arena as a major issue. Poli tIcal for localities processes are not very efficient for re­ 3) des ignate a state coord inat ion solving complex technical issues, and the a~ency public interest is best served by a pro/!ram 4) ass ist in delineat ion of flood designed to protect the public against harms hazard areas required to give the issue political sa­ 5) establish minimum standards for l ience. Th is goal can best be served by a floodplain regulation strategy of identifying situations likely to 6) assist localities in develofing make flood problems salient, monitoring floodplain management pans to detect trends toward such s ituat ions, and 7) recommend pr ior it ies for rate acting to reverse detected trends in their making studies early stages. 8) communicate floodplain informa­ tion to localities and the The support of Senator Jake Garn of an public amendment passed to require a study of 9) participate in emergency special flood hazard situations in Utah to be preparedness programs completed by March 31, 1980 (Salt Lake City 10) assist communities in dissemi­ Tribune, July 16,1979) suggests that con­ nat ing informat ion on minimum flicts between FEMA and several Utah com­ elevations for structures munities (e.g., Springville and Payson) may 11) advise public and prIvate already be approach political salience. agencies on the avoIdance of The polIt ically mot ival ing issue at th is activities that mIght aggravate point does not relate to any sense of inade­ flood problems quate protection but rather to a feeling 12) require floodplaIn uses to that the program is unnecessarily restricting conform to water quality new development by mapping larger areas than regulat ions to avoId pollut ion should be included in the floodplains and dur ing floods belng too rigid in required regulatIons. 13) provide local communllies with information on the insurance The deciSIon making dynamics currently program establishing floodplain occupancy patterns and existin~ Utah flood hazard situations 14) assure consistency of flood­ plain plans with other planning suggest the followin~ potential sources of activities politically salient problems. 15 ) amend state recording acts to 1. A large flood or group of floods permi t record ing that a parcel over the state inflicting major dama~e or is in a flood zone dnd that a loss of lIfe. The salience would be even structure has been granted a larger should the events be associated with a variance (thereby raising structural failure of measures counted on as insurance rates) providing protection. 16) assure coordination between the state coordinating agency and 2. A lack of coordination in municipal any coas tal zone management stormwater programs between adjacent munici­ program palities causing the pro~ram of one to 17) notify FIA of communIty viola­ inflict major damages in the jurisdiction of tions the other. 18) assist In resolvIng floodplain management conflIcts among 3. Federal requirements for community communi ties participatIon in the flood insurance program being perceived as so stringent that the Examinat ion of th is state role makes communities feel economic hardship or for several points clear: 1) the role described other reasons consider it in their own best IS to facilitate the FEMA program and does interest to resist. not take into account state interests as 4. Conflicts between environmental and determined from a state perspective, 2) the development interests over the use of flood­ federal regulations require signifIcant plain land. expenditure of state funds but do not provide flexibility for the state to spend Perspective for Recognizing t hose moneys in ways that seem best from Sallent Issues the state viewpoint, 3) an effective state program needs to relate to all state inter­ The above or other potent ially salient ests and to the total de facto flood program issues are most likely to come to the atten­ In the state and not just to the flood tion of state officials as citizens feel insurance and community floodplain management adverse impacts and aggregate their concern components. to a high enough level to be important for state government. The most probable direction Basis for Long Run Objectives of aggregation is through lower level govern­ ments or legislat ive represent at ives within An earlier section of this report the governmental dimension. The ag~regation proposed that one goal of the administrators would be reinforced should feel develop of a state flood control program should be to within the other dimensions that existing

18 situation is too large an economic burden, 2. Scope of Control. Any program would too restrictive on individual rights, or potentially be statewide in jurisdiction threating preservation of important environ­ though it would be possible to concentrate mental values. The monitoring for potential­ the effort in areas of particular appli­ ly salient issues should keep an eye on how cability such as the rapidly growing com­ these decisions are aggregating in all these munities along the Wasatch Front. Expertise dimensions. is available within the state and could be focused on the problem with manpower and budget reallocations. Perspective for Flood Program Operation 3 . Val u e s . Wh i 1 est ate goa 1 s wit h Any action on the part of Utah state respect to flood control have never been government should be targeted to deal explicitly defined, several studies have with specific emerging salient issues. The produced helpful models for inferr ing local ones listed above are only suggestive. or state goals. For example, Larson et al. Before implementation, a contemplated action (1979) describe how a model they call PROP­ should be evaluated in terms of its technical DEMM was applied to determine certain state feasibility to achieve the desired results goals with respect to water and land planning and its economic feasibility in terms of a in the Uintah Basin. magnitude of achievement that justifies the effort. 4. Time Frame. Except for issues relating to state construction of structural The sorts of targeted action the state flood control works (currently rather un­ will be able to employ will depend on the likely), a time dimension of about 10 years perspective within which the state will be would seem to be reasonable for watching operating as defined by the four elements budding salient issues. reviewed above (Larson et al. 1979): The organization of a state program also 1. Range of Action. Utah state govern­ needs to establish appropriate guidance and a ment is currently very limited in its forum for decision making. Practices need to capability to implement either a structural be established for evaluating specific or nonstructural flood control program. problems and present ing the findings to an It is difficult to see how the state can appropriate group for action. Perhaps the become effective in either aspect without current Board of the Division of Water significant additions or shifts in manpower Resources or some simi lar board could be and budget. used.

19 CHAPTER III

FLOOD HAZARD IN UTAH

Introduction Table 1. Record Utah snowpack accumulations (for stations with over 40 years of In terms of loss of life, the greatest record) . fl(}od risk in Utah is associated with flows w.hich rise with very little warning in moujltaIn canyons. The greatest risk to Water property occurs as mountain canyons discharge No. Station Elev Date Content water, mud, and debris onto alluvial fans and Inches other lands along the borders of valley or desert areas. Relatively less severe problems 1 Beaver CR. RS 7,500 4/01/52 18.6 are associated with riverine flooding and 2 Bryce Canyon 8,000 4/01/37 15.3 with thunderstorm runoff from urban areas. 3 Buckboard Flat 9,000 4/01/52 26.6 .In order to develop a better understanding of 4 Burts-Miller Rch 7,900 3/29/50 10.1 these problems, information will be presented 5 Camp Al tamont 7,300 3/29/52 36.2 on 1) the magnitude of major historical 6 Daniels-Straw 8,000 3/27/52 33.3 precipitation events, 2) the magnitude 7 Dry Bread Pond 8,230 4/02/52 32.1 of major recorded r unof f event s. and 3) 8 Duck Creek Rs. 8,700 3/28/69 34.4 descriptions of historical floods. 9 Dutchman Rs. 7,560 4/01/52 34.6 10 East Portal 7,560 3/28/52 29.4 Major Precipitation Events 11 Fish Lake 8,700 3/28/52 18.8 12 Franklin Basin 8,020 3/30/71 45.8 Snow depths in the higher mountains in 13 GBRC Hdquarter 8,700 3/27/52 35.0 Utah. can reach over 200 inches by April 1, 14 GBRC Meadows 10,000 3/28/52 50.4 and water contents of 40 or 50 inches have 15 Garden City Smt. 7,600 3/30/36 31.9 been recorded. A quick thaw or rain on 16 Gooseberry RS 8,400 4/23/72 19.2 snow can cause significant downstream flood­ 17 Gooseberry Res. 8,700 3/28/52 41. 3 18 Harris Fla t Rs 7,700 3/28/69 24.6 i ng ~ Table 1 shows the larges t recorded hIstorIcal snowpack accumulations at Utah 19 Hewinta GS 9,500 4/23/74 15.2 locations shown on Figure 5. 20 Hobble Cr. Smt. 7,420 3/27/52 30.1 21 Hole-In-the-Rock 9,150 4/01/52 10.7 Intense local thunderstorms occur in 22 Huntington-H 9,800 3/28/52 51. 1 both mountains and valleys. Peak intens it ies 23 Indian Canyon 9,100 3/31/52 25.7 tend to be higher in the mountains (with some 24 Jones Ranch 7,600 3/29/52 17.5 25 Kimberly Mine 9,300 3/25/52 31.0 r~verse trend at the highest elevations) and In the southern part of the state where 26 Kings Cabin L 8,600 3/31/32 15.7 warmer air masses bring more moisture into 27 Kings Cabin U 8,730 3/30/52 18.4 the state. More widespread storms associated 28 Lake Fork Mt. 10,200 3/26/52 21.6 with tropical disturbances occasionally enter 29 LaSal Mtn Lwr 8,800 4/01/52 22.3 the state in the late summer or fall from the 30 Long Valley Jc 7,500 2/27/69 19.4 southwest, and, less severe but more general 31 Mammoth Rs-Ccr 8,800 3/28/52 43.7 WInter or sprIng storms associated with low 32 Mill D So Fork 7,400 4/03/52 34.4 pressure areas moving westward from the 33 Monte Cristo 8,960 4/02/52 41.9 Pacific enter more often and from the north­ 34 Mosby Mountain 9,500 4/01/52 19.2 west. These widespread storms seldom bring 35 Otter Lake 9,300 3/31/52 32.0 the larger rivers to flood stage (the Decem­ 36 Panguitch Lake 8,200 3/23/37 13.0 ber 19ft6 flood on the Virgin River was an 37 Paradise Park 10,100 4/22/69 22.4 exceptlOn) because their less intense rain­ 38 Parleys C Smt 7,500 3/26/52 32.3 fall does not generate much runoff from 39 Redden Mine L 8,500 3/27/52 34.2 Utah's typically parched soils. 40 Seely Creek Rs 10,000 3/27/52 41. 2 41 Silver Lake 8,730 3/26/52 38.2 Peak recorded 24-hour precipitation 42 Smith Morehouse 7,600 3/29/52 24.3 events are shown on Table 2 for the Utah 43 Soapstone Rs 7,800 3/29/52 24.1 gages with more than 55 years of record. The 44 South Fork Rs 6,100 3/29/52 22.1 locatlons of these gages are also shown on 45 Strawberry Dvd 8,000 3/28/52 43.4 Figure 5. While few Utah gages have long 46 Timpanogos Cave 5,500 3/29/52 14.5 term records of gaged ralnfalls for periods 47 Timpanogos Dvd 8,140 3/28/69 44.7 shorter than a day, Davis (1970) tabulates 48 Tony Grove RS 6,250 3/26/36 25.6 values over 50-year periods of 1.78 inches 49 Trial Lake 9,800 5/20/50 42.2 for 1 hour. 2.06 inches for 6 hours· and 50 Webs ter Fla t 9,200 3/24/69 38.6 2.26 inches for 24 hours for Modena a~d of 51 Big Flat 10,290 4/01/52 35.0

21 1.17 inches for 1 hour, 1.28 inches for provide a reasonable gu idel ine as to the 6 hours, and 2.72 inches for 24 hours for maximum rainfalls one could expect for Salt Lake City. According to the Utah various durations in Utah. State Climatologist, record amounts for anywhere in Utah by duration include 2.1 In NOAA Atlas 2, Miller et a1. (1973) inches for 1 hour at Blanding, August 1968; use frequency analyses of all Utah precipita­ 6.0 inches for 12 hours at Bug Point, tion stations with more than 10 years of September 1970; 19.1 inches for "1 month at record to plot isohyetal maps for Utah of 6- Buckboard Flat, October 1972; and 69.7 inches and 24-hour precipitation amounts for various for 1 year at Alta in 1971. These Utah return periods including the 100-year. The records are plotted on Figure 6 (beside the 6-hour amounts are generally about 2.6 inches world records from Linsley et al. 1975) and in the mountains above the Wasatch Front and

Q14. Q 13. Q18.

Q 15 • • 812 Q53 P27 ••• 815 .Q8 848 \ • • Q7 P12 ••• Q~16 PI7 UTAH .19 • Q2 6 Q 17 P 34 o 10 20 30 40 SO ~ ! , ! , ! .p 833 •• Q5 51. ... SCALE Of MILES Q 24.,-J87 Q6 • Q3 P28 .. -----""'- Q25 ....'"Q22 Q59 Q 60 Q 26 Q23 Q 21 L.... Q~4~~_ .... -T_----., Q41.:ia:Q2084 819 .821 Q62 P33 Q40~ Q39 Q32 Q80---\.Q6il827 38~ 5:,-.8.iiS;;~1 837.\e ~826 PI3 \ 83 Q33e.. ~JQ82.\ IQ61 P~2.

Q58 • 83 • P23 • P26 • • 8311/ Q42 850 ~ .82 Q52 •• 88 ~P7 • P4 L...-ri----!.e • 8 30 Q4...:4:....------I" I 818. QI03 QI02 QIOI • • • Q 100 • P 5 .P29 • PI6 • ·Q104 Figure 5. Location map for record snowpack accumulations (8), precipitation amounts (P), and stream flows (Q).

22 about 2.0 inches in the Cltles. Statewide reported results. For comparlson, the extremes range from 1.7 inches in the Western depth-area curve developed for Utah by Desert and around Bear Lake to 3.2 inches in Miller et a1. (1973) is also shown. the mountains above Cedar City. The 24-hour amounts range from 2.4 to 4.4 inches. Farmer and Fletcher (1971) present The U.S. Geological Survey has 105 magnitudes of the 10-year, I-hour event range stream gages in Utah that have more than 20 from 0.37 to 0.86 inches for locations in years of record. The peak recorded flows and Northern Utah, 0.62 to 0.86 inches in Central estimated 100-year flows (based on the log­ Utah, and 1.11 to 1.50 inches in Southern Pearson Type I I I d istr ibut ion fitted by the Utah. Fletcher et a1. (1977) estimated method of moments and using station skewness) rainfalls for various Utah watersheds ranging are shown, both as a flow rate (cfs) and as a from 1.0 to 1.4 inches in 1 hour. Their flow rate normalized by watershed area (csm), intensities for 10-minute durations ranged in Table 3. The 100-year flows are plotted from 3.0 to 4.1 inches per hour. versus tributary dra area in Figure 8 in order to provide a rough indication of The Corps of Engineers (1976) used a the 100-year flood peak one may expect for network of 14 recording gages and 40 non­ various drainage areas. recording gages over a 350-square mile area for 6 years to develop storm isohyetal maps From Figure 8, one can see that a number and depth-area-duration curves for nine of watersheds in the Colorado River basin storms. Figure 7 provides a normalized have recorded flood peaks several times depth-area-duration curve derived from the larger than any of those in the Great Basin of comparable size. Straightline upper envelopes were drawn for both basins with the Table 2. Record 24-hour precipitation amounts results for the Colorado River Basin of for Utah (for selected stations with O 22 55 years or more of record). Q = 5080 A . 5 . (1) and for the Great Basin of Amount No. Station Name Date (inches)a Q = 1330 AO. 225 . (2) where in each case Q is a flow in cubic feet 1 Alpine 3/24/16 2.40 per second and A is the dra area of the 2 Alton 3/03/38 3.55 tributary basin in square miles. 3 Beaver 9/30/11 2.17 4 Blanding 8/01/68 4.48 Also plotted on Figure 8 are an average 5 Bluff 7/29/66 3.60 curve for all basins in extreme south Utah 6 Brigham Ci ty 4/13/72 2.19 derived from Berwick (1962) and an average 7 Bryce Canyon Park 9/11/39 4.09 curve for the Georgia Mountains from Golden 8 Deseret 2/10/15 2.00 and Price (1976). A comparison between these 9 Escalante 10/6/16 3.39 two curves shows the hazard to be not too 10 Filmore 3/11/40 2.32 different in this portion of Utah, that with 11 Fort Duchesne 9/29/05 4.06 the most severe flood hazard, for smaller 12 Garland 8/19/77 2.87 basins but to become progressively less for 13 Grantsville 9/17/47 1. 74 basins larger than 100 sq. mi. According to 14 Heber 1/17/09 2.20 Golden and Price (1976) the coefficients in 15 Jensen 2/26/69 1.60 the 100-year flood predict ing equat ions for 16 Kanab 12/6/66 2.80 the various hydrologic r ions of Georgia 17 Laketown 8/18/77 2.47 range from 215 to 862, a or of 4. Ac­ 18 Levan 4/30/95 2.85 cording to Berkwick (1962), mean annual flood 19 Logan (USU) 3/12/46 2.17 peaks from Utah predict equations vary by 20 Manti 6/31/43 1. 75 a factor of about 35. One would thus expect 21 Milford 10/6/16 1.92 all of the Georgia data to plot in a much 22 Minersville 8/21/71 2.20 narrower band at the top of the Utah data. 23 Modena 9/18/25 2.26 Ratios of 100-year to mean annual flood peaks 24 Moroni 6/01/43 2.16 in Utah basins vary from about 2 around Salt 25 Oak City 7/27/29 2.27 Lake City to about 7 in the southeastern part 26 Panguitch 3/03/38 1.90 of the state. Coefficients of variation 27 Richmond 8/18/77 3.26 (standard deviations divided by the means of 28 Riverdale Pw Hs. 8/12/30 2.47 the logarithms of the annual flood peaks) 29 St. George 8/31/09 2.40 30 Sp. Fork Pw. Hs. 7/16/74 2.87 trend to be inversely related to drainage 31 Thompson's 9/13/27 1.95 areas averaging 0.09 for 9 basins larger than 32 Tooele 11/15/58 2.65 500 sq. mi. and 0.34 for 11 basins smaller 33 Wendover 8/11/49 1.39 than 5 sq. mi. (Tooley 1980). 34 Woodruff 5/24/07 2.20 The exp,onent of 0.225 for the envelope curves on Figure 8 is extremely small. Values ~tah' s maximum recorded 24-hour precipitation was for the five hydrologic regions of Georgia 6.00 inches near Bug Point, September 1970. range from 0.57 to 0.68 (Golden and Price

23 1976). Cummans, Collings, and Nassar (1974) River, 15,000 cfs for the Price River at report 0.86 for Western Washington. However, Price, 88,000 cfs for the San Juan River at Berwicks (1962) curves imply values for nine Blu ff, and 11,500 cf s for the Weber River at hydrologic regions of Utah ranging from 0.40 Ogden. Flood peaks .from a drainage area of a all the way up to 0.98, with the highest given size were found largest in the south­ values in steep mountain areas in the eleva­ eastern portion of the state. Fletcher el tion ranges of 6,000 to 10,000 feet and the al. (1977) plotted flood frequency curves for lowest values in more gently sloping areas. 25 Utah stations and used the resulting The tendency is for flood peaks to increase estimates of the 100-year flow and infor­ only slightly less than directly propor­ mation on watershed characteristics to derive tionally to drainage areas in rugged mountain an equation for estimating the 100-year flood terrain but increase very little, and some­ peak from the drainage area, the elevat ion times decrease at lower altitudes. difference between the highest and lowest points in the watershed, and a rainfall Regional Flood Frequency Studies erosivity index read from a map of the state. Berwick (1962) used the basic data available as of that date to develop a Flood Peaks Estimated series of curves and maps that could be used from PrecipItation to estimate flood peaks for any frequency up to the 2 percent event for any watersbed in Flood control- and floodplain management Utah, outside the Great Salt Lake Desert and efforts often require estimates of peak flood Snake River Basins, given the drainage area flows at locations where nO'records are and mean basin elevation. He plotted curves available. Rather than using regional flood of 50-year flood peak versus river mile for frequency studies such as those described the major streams. Peak values shown include above, most flood flows are estimated from 78,000 cfs for the Colorado River at Moab, information on precipitation and watershed 70,000 cfs for tbe Green River at Green char act er is tics. For example, the Corps of

2000 I I I I I II lOgo I ~ 8 0 'bM=' " "..- 600 '~ ! ! - 400 =t=t ~p - 200 i ' ~ 100 I ~ 80 /W kf- .... 0 A"'" - wZ 60 >A 00 40 oc e'" /.~ ~ ~LTA 0::- ~eC /e , V"" - O~ 20 I ~o(\e /. • i Y I I( J U..-.: A· I I ~e~~ W- 10 BUCKBOARD FLAT ...,I o::f!: 8 \)'\G"/ 6 I, ...--- - .U ~ ..., XW 4 /"" ...... i"'" BUG POINT «0:: -/ ". =i ~a. 2 V i / BLANDING I ~ I i .8 ".. - .6 - -i,./" I - 1=$ -i A """" .2 i

.1 ,I I I 2 4 6 8 10 20 4060 3 6 9 12 1824 5 10 2030 2 3 6 9 12 24 l~ ______~~~ ______~Jl~ ____~~~ ____-JA~ ______~~, ______~)\ ______" I

MINUTES HOURS DAYS MONTHS DURATION

Figure 6. Maximum precipitation recorded in Utah for various durations.

24 Engineers' afproach to estimation of 100-year used to estimate the initial moisture loss flood peaks uses a 100-year precipitat ion (inches) and loss rate during the storm event estimated from rainfall records, (inches per hour). Pat terns observed in callbration of a storm runoff model to these losses are then used to est imale the estimate the runoff volume from such an two loss coefficients for estimating runoff event, and application of a unit hydrograph volume by time interval dur ing the storm to the estimated volume to estimate the peak selected to represent a desired frequency. flow. The precipitation-frequency relation­ These time-interv~l runoff volumes are ships are based on long-term gaged records then converted to a storm hydrograph by the for Utah stations and checked against region­ unit hydrograph method. Subwatershed hydro­ al envelope precipitation-duration curves. graphs are routed and combined downstream as Regional curves express ing areal precipita­ necessary for flood-peak estimation for tion as a fraction of point amounts (such larger drainage areas. The flood peaks as Figure 7) are used to adjust station estimated for flood insurance studies for rainfall amounts downward to appropriate selected Utah drainage basins are shown in volumes over watershed areas. Table 4 and can be compared with the regional results on Figure 8. Generally the flood The Corps' HEC-l Model is used to peaks being estimated are near or above the . estimate runoff volume from storm rainfalls. envelope curves obtained by frequency analy­ For storms where both precipitation and sis of regional streamflow records. runoff volumes have been recorded, the optimizing feature of that model has been Descriptive Information on Historical Floods lInterview with Herb Hereth, Hydrologist, U. S. Army Corps of Eng ineenl, Sacrament 0 Woolley (1946), covering the period from District. June 1979. Mormon settlement in 1847 until 1939, and

1.0 +-"""""'==------ir------j------i

c: o += 0.95~------~------~._--~------~ U) 0 0:= c: .~ o (.) :;::~ .Eo.. 0.90;------+------+-~~---~~~ 0.- '0 .!: (I)lIo..o.. 0 0.._ -0 0.85 ;------t------t------"'<:----j o c: ~ 0 <.(+= Corps of Engineers (.) o (1976) ------lIo.. LL 0.80~------~------~------~ o

0.75+-______+- ______~------~--- 0.1 1.0 10.0 100.0 Drainage Area in Square Mi les Log Scale

Figure 7. Normalized Depth-Area-Duration Curve derived by enveloping project cloudburst data (6-hour).

25 Table 3. Record gaged streamflow in Utah (flows of record at all sites with more than 20 years of gaged record).

Yrs. of Drainage Flow of Record 100-yr flow Location record Da te Flow CSM (~"2a) (cfs) CZf;;) CSM Great Basin Bear River near Utah-Wyoming State 1943-75 172 6-6-68 2980 17.3 3305.6 19.2 Line Big Creek near Randolph, Ut. 1940-70 52.2 7-11-57 337 7.2 351.9 6.7

Bear River near Evanston, Wyo. 1914-56 715 6-14-21 3690 5.2 4137.7 5.8

Mill Creek at Utah-Wyoming State 1943-62 60 6-7-57 690 11.5 908.4 15.1 Line Bear River near Woodruff, Ut. 1942-61 870 4-28-52 3010 3.5 3400.1 3.9

Woodruff Creek near Woodruff, Ut. 1938-75 56.8 5-25-50 528 9.3 679.4 12.0

Bear River near Randolph, Ut. 1944-75 1616 5-8-52 2660 1.6 3623.3 2.2

Bear River below Pixley Dam NR 1942-75 2032 3-25-56 2300 1.1 3356.7 1.7 Cokeville, Wyo. Smith's Fork near Border, Wyo. 1942-75 165 6-18-71 1610 9.8 1789.6 10.8

Bear River at Border, Wyo. 1930-75 2486 5-11-52 3680 1.5 4734.6 1.9

Thomas Fork near Wyom-Idaho State 1950-75 113 5-14-71 1040 9.2 1881. 3 16.6 Line Bear River at Harer, Idaho 1914-75 2839 5-7-52 4440 1.6 5974.3 2.1

Montpelier Cr. at irrigators Weir 1943-75 49.5 5-18-50 224 4.5 269.5 5.4 in Montpelier, Idaho Cottonwood Creek near Cleveland, 1939-75 61. 7 5-16-75 788 12.8 949.5 15.4 Idaho Cub River near Preston, Idaho 1940-75 31. 6 6-16-75 753 23.8 887.7 28.1

Logan River above State Dam NR 1896-1975 218 5-24-07 2480 11.4 2268.0 10.4 Logan, ut. Blacksmith Fork AB UPL Co.'s Dam 19l4-75 268 5-4-52 1400 5.2 1825.0 6.8 near Hyrum, Ut. Devil C. AB Campbell C. NR Malad C. 1939-61 13 8-25-61 194 14.9 240.7 18.5 Idaho Weber River near Oakley, Ut. 1905-75 163 6-13-21 4170 25.6 3717.0 22.8

Weber River near Coalville, Ut. 1927-75 438 5-6-52 2190 5.0 2793.7 6.4

Chalk Creek at Coalville, Ut. 1905-75 253 4-28-52 1540 6.1 1331. 7 5.3

Lost Creek near Croydon, Ut. 1921-67 133 5-10-23 770 5.8 991.1 7.5

Hardscrabble Creek near Portorville, 1942-70 28.1 8-20-45 464 16.5 541.9 19.3 Ut. South Fork Ogden River near 1921-75 148 5-3-52 1890 12.8 2572.2 17.4 Huntsville, ut. Farmington C AB Diversions NR 1950-75 10 6-6-75 366 36.6 527.5 52.8 Farmington, ut. Centerville Creek AB Div Near 1950-75 3.15 5-20-75 35 11.1 54.2 17.2 Centerville, Ut. Salt Creek at Nephi, Ut. 1951-75 95.5 8-1-68 832 8.7 776.9 8.1

Spanish Fork at Thistle, Ut. 1908-74 490 5-4-52 1800 3.7 1621. 5 3.3

Spanish Fork at Castilla, Ut. 1890-1975 670 5-3-52 3610 5.4 2678.3 4.0

Spanish Fork near Lake Shore, Ut. 1904-73 700 4-28-52 3020 4.3 1839.1 2.6

Hobble Creek NR Springville, Ut. 1904-73 105 5-4-52 1250 11.9 1214.7 11. 6

26 Table 3. Continued.

Location

Provo R. NR Ut.

Provo River near Hailstone, Ut. 1950-76 233 6-4-57 3880 16.7 4542.9 19.5

South Fork Provo R. at Vivian 1912-63 30 2-1-63 500 16.7 201.7 6.7 Park, Ut. Dry Creek near Alpine, Ut. 1948-73 9.82 8-25-61 597 60.8 464.0 47.3

American Fork AB Upper PP NR 1927-75 51.1 8-3-51 645 12.6 656.9 12.9 American Fork, Ut. Little Cottonwood C. NR Salt Lake 1912-63 27.4 6-11-21 762 27.8 812.9 29.7 City, Ut. Big Cottonwood C. NR Salt Lake 1901-63 50 6-7-12 848 17.0 847.2 17.0 City, Ut. Mill Creek near Salt Lake City, 1899-1963 21. 7 5-20-49 152 7.0 150.2 6.9 Ut. Emigration Cr. near Salt Lake 1902-58 18 4-26-52 156 8.7 137.1 7.6 City, Ut. City Creek near Salt Lake City, Ut. 1899-1963 19.2 5-30-21 163 8.5 149.4 7.8

Sevier River at Hatch, Ut. 1912-75 340 5-26-22 1490 4.4 1723.7 5.1

Antimony Creek near Antimony, Utah 1947-75 97 8-3-59 669 6.9 1143.6 11.8

East FoikSevier River near 1913-75 1250 5-12-41 2030 1.6 1838.5 1.5 Kingston, Ut. Sevier River Below Piute Dam 1912-75 2440 5-23-22 2600 1.1 1794.1 0.7 NR Marysville, Ut. Clear Creek at Sevier, Ut. 1912-58 169 8-7-41 487 2.9 724.5 4.3

Salina Creek at Salina, Ut. 1914-75 290 8-26-70 1800 6.2 2333.1 8.0

Pleasant Creek near Mount Pleasant, 1946-75 16.4 7-24-46 2060 125.6 1310.0 49.4 Ut. Chalk Creek near Fillmore, Ut. 1914-71 60 7-31-61 1850 30.8 1122.0 18.7

Beaver River near Beaver, Ut. 1914-65 82 7-22-36 1080 13.2 1371.3 16.7

Beaver River at Rocky Ford Dam 1914-75 512 6-10-21 727 1.4 831.9 1.6 NR Minersville Coal Creek near Cedar City, Ut. 1916-75 80.9 7-23-69 4620 57.1 7871.8 97.3 Columbia River Basin 7-16-74 Clear Creek near Naf, Idaho 1910-70 19 6-15-67 386 20.3 368.8 19.4 Colorado River Basin Castle Creek above diversions near 1951-75 7.58 9-19-72 69 9.1 83.1 11.0 Moab, Utah Courthouse Wash, near Moab, Ut. 1950-75 162 8-5-57 12300 75.9 11476.2 70.8

Mill Creek near Moab, Ut. 1915-75 74.9 8-21-53 5110 68.2 11697.6 156.2

Hatch Wash near La Sal, Ut. 1950-71 378 8-20-70 4650 12.3 5403.7 14.3

Indian Cr. AB Cottonwood Cr. NR 1950-71 31.2 8-28-71 2330 74.7 2095.6 67.1 Monticello, Ut. West Fork of Smith Fork NR 1940-75 37.2 6-10-65 2100 56.5 1512.2 40.7 Robertson, Wyo. Middle Fork Beaver Creek NR 1949-70 28 6-11-65 775 27.7 962.4 34.4 Lonet·ree, Wyo. Ashley Creek near Vernal, Ut. 1912-75 101 6-11-65 3500 34.7 2980.2 29.5

Dry Fork above Sinks near Dry 1939-75 44.4 6-10-65 1010 22.7 1282.8 28.9 Fork, Ut. North Fork of Dry Fork near Dry 1946-75 8.62 6-5-68 169 19.6 208.8 24.2 Fork, Ut. Dry Fork BLW Springs NR Dry Fork, 1904-69 102 6-11-65 974 9.5 1363.3 13.4 Ut.

27 Table 3. Continued.

Yrs. of Location record

Dry Fork at Mouth Near Dry Fork, 1955-75 1210 1623.1 Ut. Ashley C. Sign of the Maine N 1900-65 241 6-11-65 4110 17.1 3637.0 15.1 Vernal, Ut. Duchesne R. at Provo R. Trail 1930-54 39 6-13-53 1180 30.3 1262.8 32.4 NR Hanna, Ut. Duchesne River near Hanna, Ut. 1922-63 78 6-16-63 17500 224.3 1830.3 23.5

West Fork Duchesne River near 1923-75 61 6-5-67 758 12.4 874.4 14.3 Hanna, Ut. Wolf Creek above Rhodes Canyon 1946-75 9 6-15-75 74 8.2 88.0 9.8 near Hanna, Ut. Duchesne River near Tabiona, Ut. 1919-74 352 6-16-63 5260 14.9 2602.5 7.4

South Fork Rock Creek near 1954-75 14 6-16-75 186 13.3 230.4 16.5 Hanna, Ut. Rock Creek near Hanna, Ut. 1950-75 120 6-13-65 2300 19.2 2665.3 22.2

Rock Creek near Mountain Home, Ut. 1938-75 149 6-18-71 2920 19.6 2943.0 19.8

Duchesne River at Duchesne, Ut. 1918-69 660 6-10-22 4420 6.7 4452.8 6.7

Currant C. BRed Ldge Hlw N. 1946-75 48 5-21-75 946 19.7 999.8 20,8 Fruitland, Ut. Water Hollow near Fruitland, Ut. 1946-75 14 7-18-54 133 9.5 186.3 13.3

Currant Creek near Fruitland, Ut. 1935-75 140 5-4-52 1260 9.0 1095.4 7.8

Lake Fork River above Moon Lake 1933-75 78 6-26-44 2700 34.6 2959.8 37.9 NR Mtn. Home 6-17-71 Yellowstone River near Altonah, Ut. 1945-75 131 6-19-49 1880 14.4 1976.7 15.1

Uinta River near Neola, Ut. 1925-75 160 6-11-65 5000 31.3 4119.1 25.7

Farm Creek near Whiterocks, Ut. 1950-75 14.9 6-3-68 350 23.5 584.9 39.3

Whiterocks River near Whiterocks, 1902-74 113 6-20-22 2750 24.3 3067.3 27.1 Ut. White River near Watson, Ut. 1904-75 4020 7-15-29 8160 2.0 8988 2.2

Minnie Maud Creek near Myton, Ut. 1952-75 30 8-25-61 1370 45.7 2299.8 76.7

Minnie Maud C. at Nutter Ranch NR 1947-69 231 8-25-55 1370 5.9 1794.1 7.8 Myton, Ut. Fish Creek above Reservoir near 1932-75 65 5-20-73 1160 17 .8 1277.5 19.7 Scofield, Ut. White River near Soldier Summit, 1940-67 53 5-5-52 1120 21.1 866.3 16.3 Ut. Price River near Heiner, Ut. 1935-69 455 9-13-40 9340 20.5 7147.5 15.7

Price River at Woodside, Ut. 1909-75 1500 9-10-61 8500 5.7 13186.4 8.8

Saleratus Wash at Green River, 1949-70 180 9-21-62 14200 78.9 13842.4 76.9 Ut. Huntington Cr. NR Huntington, Ut. 1909-75 188 8-20-30 2500 13.3 2689.1 14.3

Ferron Creek (Upper Station) NR 1912-75 138 8-27-52 4180 30.3 4243.5 30.8 Ferron, Ut. 6-6-75 Muddy Creek near Emery, Ut. 1909-75 105 5-10-52 3340 31.8 3880.2 37.0 lvie Creek above Diversions NR 1951-74 50 7-18-65 1240 24.8 1728.7 34.6 Emery, Ut. North Wash near Hite, Ut. 1950-70 140 8-7-52 8900 63.6 15440.8 110.3

Pine Creek near Escalante, Ut. 1951-75 78 8-2-67 1010 12.9 2425.9 31.1

28 - Table 3. Continued. Yrs. of Drainage Flow of Record 100-yr flow Location record are~ Date Flow CSM Flow CSM (mi ) (cfs) (cfs) Escalante River near Escalante, Ut. 1910-75 310 8- -53 3450 11.1 8427 .4 27.2

East Fork Boulder Cr. Near 1951-72 21.4 5-20-64 483 22.6 646.7 30.2 Boulder, Ut. San Juan River near Bluff, Ut. 1915-75 23000 9-10-27 70000 0.3 71269.9 3.1

North Fork Virgin River near 1913-75 350 12-6-66 9150 26.1 10339.2 29.5 Springdale, Ut. Virgin River at Virgin, Ut. 1910-71 934 12.,.6-66 22800 24.4 22825.3 24.4

Santa Clara R. ab Winsor Dam N 1942-71 338 8-24-55 6190 18.3 13219.8 39.1 Santa Clara, Ut. River at Littlefield, Ariz. 1930-75 5090 12-6-66 35200 6.9 34655.5 6.8

100,000

50eOA°.225

0:~\ 0' 1330AO. 225 ~\ 10,000 0::: a.W I­ W W A LL Ia (.) EI al 1,000 o::.> z IJ!J. Streams in Colorado River Basin G Streams in Great 8asin

100

Utah data from U.S.G.S Average Georgia Mountain Curve from Golden and Price (1976) Average South Utah Curve Estimated from Barwick(1962)

10~--~------'~------r------~------~------~ 10 100 1000 10,000 100,000 DRAINAGE BASIN AREA I N SQUARE MILES (A)

Figure 8. 100-year flows calculated for Utah drainage basins with 20 or more years of record.

29 But ler and Marsell (1972), extend ing the were reported. Of the 228 incorporated record to 1969, identified 1339 cloudburst. communities and unincorporated places of floods as having occurred in Utah and com­ 1,000 or more population, according to the piled physical descr ipt ions of the flood 1970 census, 131 experienced at least one events and tabulated data on deaths and cloudburst flood during the 30-year period. damages. The informat ion was collected from August accounted for 44.0 percent of the newspaper accounts and U. S. gov'ernment agency events followed by July with 29.1 and Septem­ (Economic Research Service, Forest Service, ber with 12.2. A few events occurred in Soil Conservation Service, and Geological a 11 the other months except February and Survey) records and tabulated them by com­ March. munity, county, and year. Many of the accounts describing these During the 31 years covered by Butler cloudburst floods noted large volumes and Marsell (1972), 836 cloudburst floods of debris being carried with the water. From

Table 4. Flood insurance study flood peaks estimated for selected Utah drainage basins.

Drainage Peak Discharges (cfs) Community Flooding Source and Location Are"?z (Mile ) 10 yr 50 yr 100 yr 500 yr 9,980 25,500 3.5 miles upstream from the mouth of Mill Creek at confluence with Colorado River Pack Creek 63.0 2,800 7,300 10,400 18,900 Mill Creek Drive Helper Price River 491.0 3,736 7,804 10,208 17,827 Above confluence with Spring Glen Wash Above confluence with Spring Canyon Wash 465.0 3,635 7,594 9,934 17,349 Spring Canyon Wash at mouth 24.0 887 2,879 4,378 9,744 Provo Provo River 680 1,800 2,600 3,200 3,800 1 mile below mouth of Provo Canyon Rock Canyon Creek 9.4 865 1,710 2,100 3,200 at mouth of Rock Canyon Little Rock Canyon Creek 0.8 305 526 637 916 at mouth of Little Rock Canyon SunnYSide Grassy Trail Creek cross section A 43.6 810 2,650 3,320 6,060 North Slope Tributary cross section B 2.5 280 650 760 1,140 Springville Hobble Creek 110 650 970 1,800 4,500 at canyon mouth Orangeville Cottonwood Creek 93 3,230 5,290 6,240 8,800 Main Street Bridge (area below Joe's Valley Dam) Northerly Tributary 1.3 60 244 390 960 to Cottonwood Creek Payson Peteetneet Creek 27.6 450 800 1,000 1,400 above Payson Canyon mouth Bountiful Barton Creek 500 West & US 89 & 91 6.6 100 230 250 260 750 East 5.5 100 570 1,100 2,700 Mill Creek 1-15 12.0 220 300 310 310 Main Street 10.6 220 1,000 1,600 1,600 Orchard Drive 10.5 220 1,000 2,000 4,400 Stone Creek Main Street 7.0 50 230 575 1,450 Below confluence with North Fork Stone Creek 6.9 165 675 1,460 3,000 Davis Boulevard 4.4 120 860 1,430 2,500

30 many mountain canyons, surface runoff is Creek, and Montezuma Creek) totaled $589,000 rare, and the floods flush accumulated plant of which $304,000 was to roads and other litter and soil particles from clay to public facilities, $174,000 was to agricul­ boulder size from the surface slopes into the ture, $109,000 was to utility lines, and stream channel. At constriction points, $2,000 was to commercial property. No the masS is prone to snag to form temporary res ident ia1 damages were recorded. Th is dams that later break to send debris plunging damage breakdown shows that flood insurance down the canyon. The viscous mud-rock flow would have been of virtually no help during maintains its depth as it flows out of the one of the largest floods ever recorded canyon onto unconfined surfaces but eventual­ in Utah because the damage did not occur to ly halts as the water drains out the bottom. insurable property. Because of the res idual ridge, the next mud flow leaves the mouth of the canyon in a This situation occurs frequently. different direction, and an alluvial fan is Woolley (1946) summar ized that " ... more built over a series of floods. Because of than 50 percent of the floods damaged high­ its greater depth and sediment content, this ways, bridges, irrigation structures, and sort of flooding is much more destructive railroads; about 20 percent of them damaged than the floods where clear water spreads fields and crops; and about 18 percent quickly to shallow depths. Butler and flooded city streets and basements of homes Marsell (1972) noted Mant i and Mt. Pleasant with mud and debr is. In a few places small in Sanpete County as communities subject to areas of relatively high-priced land and mud -rock flows about one year in e.igh t. comfortable homes were rendered useless" (p. 123). The largest flash flood flow noted by Butler and Marsell (1972) was the event of The evaluat ion of flood hazards by the August 1,1968, where 24-hour precipitation Bear River Basin USDA tooperative River Basin es timated to have reached 6.5 inches at an Study (1977) estimated 100-year flows of 840 ungaged location near Monticello caused a cfs on the Malad River flooding 1030 acres peak discharge of 20,500 cfs on Cottonwood with damages to pasture land and rural roads, Wash near Blanding from a 205-square mile of 1900 cfs on the Little Bear River flooding drainage area. Downstream at Bluff, the peak 1600 acres damaging alfalfa fields and flow reached 42,000 cfs from a 340-square other croplands, and of 2500 cfs on the Logan mile watershed. The flood washed out roads, River flooding 1260 acres damaging campsites, inundated residences and businesses in Bluff homes in Logan, and agr icultural crops and to a depth of 3 feet, and stranded motorists. irrigation facilities. For the Bear River Basin in Utah, average annual flood damages The most damaging flood reported by were estimated at $275,360 for a 50,640-acre Woolley (1946) occurred on August 13, 1923, floodplain. Of these, $4,270 were res iden­ when a general thunderstorm struck the t ial, $220 were commerc ial, and $1,130 were Wasatch Front from Salt Lake City north to industrial and utilities. Again a very small t he Idaho border. The wors t flood ing oc­ portion of the damage potential is insurable curred in Farmington and Centervi lIe, where under the flood insurance program. seven drowned, and in Willard where two more drowned. Damages were est imated to Also, according to Butler and Marsel1 run into "hundreds of thousands of dollars. II (1972), about 35 people have been reported A similar storm struck on July 10, 1930, as drowned by cloudburst floods in Utah, causing an estimated $500,000 damage state­ 9 of them since 1939. The worst recent wide, with Salt Lake City, Ogden, and Farm­ event was when 5 of 26 hikers were drowned ington sustaining the heaviest losses. when caught by a cloudburst flood in Zion Nat ional Park in September 1961. Woolley Roes ke et a1. (1978) described a major (1946) reports 7 people drowned in the 1923 flood in September 1970 in the Four Corners flooding. area of southeast Utah. A Bug Point rancher measured 6.00 inches in 11 hours to establish The flood control appendix to the Water new 12- and 24-hour gaged records for Utah Resources Council (1971a) Comprehensive (previous 24-hour record was 5.08 inches near Framework Study for the Great Basin Region Provo). The largest flood flows were re­ describes the April 1952 snowmelt flood from corded on MonteZuma and McElmo Creeks and the Parleys, Red Butte, and Emigration Creeks San Juan River downstream. Two persons as inundating 75 city blocks in Salt Lake were drowned when McElmo Creek washed out a City for up to 30 days and causing $2,337,000 bridge abutment near Aneth. Montezuma in damage. In terms of resulting damage, the Creek stered a peak flow of 40,500 cfs, flooding along the Wasatch Front in the 27 times larger than the previous high in 12 spring of 1952 was the most severe in the years of record. A peak discharge of 52,000 history of the state (p. 13). Other damage cfs on the San Juan River near Bluff caused a amounts were Weber River $1,350,000, Spanish levee to fail and damaged fields and irriga­ Fork River $1,180,000, Provo River $649,000, tion facilities. The summary of flood Hobble Creek $455,000, Bear River $404,000, damages that Roeske et a!. (1976, p. 38) Jordan River $274,000, and the Ogden River adapted from field estimates by the U.S. Army $97,000. The 1952 damage total was thus Corps of Engineers for the three river $6,746,000. The flood listed as causing reaches all or partly in Utah (San Juan River the second most damage in this region was from Navajo Reservoir to Lake Powell, McElmo $477 ,000 by Bear River flooding in February

31 1962. The only other floods in the Great coefficients based on previous studies Basin portion of Utah listed as causing dam­ extended by field inspection, and an assump­ ages exceeding $110,000 are Farmington Creek t ion of flo .. conditions unobstructed by in August 1923 ($300,000), Coal Creek in Au­ debris or sediment in the HEC-2 program to gust 1921 ($218,000), and Dry Canyon (Sevier compute water surface elevat ions to "an River Basin) in August 1965 ($176,000). accuracy of 0.5 foot." The results are generally expressed in a map showing the The flood control appendix to the area subject to inundat ion by the 100-year framework study for the Upper Colorado flood and a flood hazard factor (FHF) ex­ Region (Water Resources Council 1971b) notes pressing the difference in water surface the most disastrous flood of record in this elevation between the 10 and the lOa-year part of Utah as being caused by heavy rain on floods and thereby indicating the variability snow in June 1965 along Sheep Creek, a of flood depth with frequency. The FHF will tributary of the Green River near Manila, normally be high in mountain canyons and very Utah. That flood took seven lives and caused low in the lowlands. $802,000 in damages principally to roads, bridges, and campgrounds in this mountain Those experienced in floodplain mapping recreation area. Other major events, listed generally recognize that the uncertainty in decreas ing order of flood damage caused, in water surface elevation mapping exceeds were $380,000 by the Price River near Helper a half foot even though this figure is in June 1917, $297,000 by the Strawberry and commonly quoted in flood insurance studies. nearby Rivers near Neola in June 1952, The uncertainty in estimating the FHF as $155,000 by the Green River near Jensen in the difference between two water sur face June 1957, and $120,000 by the Price River elevations is somewhat greater. near Heiner in April 1952. Only $25,000 of all these damages were to residential Cons ider ing only those uncerta int ies and commercial property. related to the open channel flow computa­ tions, the Sacramento District of the Corps The flood control appendix for the Lower of Engineers, which includes most of Utah, Colorado Region (Water Resources Council has cautioned that the HEC-2 printout should 1971c), covering the Washington County area be considered incomplete for flood hazard in Utah, records the most disastrous flood in mapping until reviewed with supplemental this area as occurring in December 1966. sound engineer ing judgment. They emphasize Several days of light rain followed by heavy that interpretation of the printout requires rain on December 6 produced,' a discharge of expertise in evaluating the reliability 22,800 cfs on the Virgin River at Virgin, of the basic data, converting the ba.sic Utah, and 32,500 cfs at Littlefield, Arizona. information into the input data for computer The flow was almost twice the previous analysis, and interpreting the output. record, but the only damage was associated Special attention needs to be given to with flooding and erosion of about 300 the variables that affect the backwater acres of agricultural land, a washing away of curves and the limi tat ions to the computer the approaches to the State Route 64 bridges, programming. and severe erosion of State Route 212 (U.S. Army Corps of Engineers 1973). The total The determination of the area flood~d damage of $962,000 was divided among $628,000 when the flow spreads out after leaving a to agriculture, $335,000 to public facili­ channel is much less precise than is the ties, and $5,000 to residential and com­ determination for confined riverine flood­ mercial buildings. The appendix tabulated no plains. Dawdy (1979) has developed a method other historical Hood as causing more than quant ifying how the flood hazard diminishes $100,000 in damage to this part of Utah. below the apex of an alluvial fan based on assumptions that each discharge down the fan Hydraulic Analysis stays in the same channel and that the chan­ nels from storm to storm are uniformly The flood hazard at a given location d istr ibuted along each contour crossing the is determined by the frequency with which fan. The FIA is beginning to use this various depths of inundation can be expected method for true alluvial fan situations, but at the site and such characteristics of the two assumpt ions of the Dawdy method are the flows as velocity and sediment content. seldom fully valid. Most s ituat ions at the Flood hazard mapping shows how the hazard mouth of Utah mountain canyons are inter­ varies over the floodplain. The conventional mediary between the assumptions of certainty approach to riverine flood hazard mapping as to channel location for the riverine is to determine the water surface profile method and complete randomness of locat ion. for the selected flood flow based on the Emp ir ical dat a are needed. Observat ions of principles of open channel flow hydraulics. flooding in Utah show that manmade construc­ The tool that has generally been used in Utah tion on alluvial fans prevents random shifts for this task is the HEC-2 step backwater in channel locat ion from storm 'to storm and computer program (Hydrologic Engineering causes flows in a given storm to disperse Center 1973). For example, the flood insur­ into many channels, but these effects need ance study for Bountiful (FIA 1978) used to be better quantified if reliable flood surveyed channel cross sections, extra cross hazard maps are to be developed for these sections near bridge locations, roughness areas.

32 Generally, the mapped floodplain areas magic boundary differentiating danger on alluvial fans have been given a flood from safety. Mapping that boundary in hazard rating of AO. AO zones are defined as alluvial areas is very uncertain. The areas subject to shallow flooding (no more area inundated by a given flow will not be than 3 feet deep) by flows not associated the same area inundated by the next flow of with a defined channeL The maps for Utah the same magnitude. Changing conditions usually indicate a maximum flood depth of one along the stream bank cause flows to break foot. out of the channel at different locations during different floods. The entire area Design Ramifications subject to flooding by flows of the 100-year magnitude is a much larger area than that The differences between the flood hazard wherein flooding can be expected one or more situations describ~d above for Utah and typi­ years out of 100. Consequently, nonstruc­ cal situations nationwide suggest that flood tural protection of the full area subject to control and floodplain management design flooding by a 100-year flow requires that the pract ices used elsewhere be reviewed for measures be employed over a much larger area effect iveness before application to Utah than would be necessary in a more humid situations. Relevant differences include: climate, and the associated greater cost makes little sense in an area where infre­ 1- Less flood hazard for a watershed of quent shallow flooding causes less damage. given size. 2. A greater portion of the total flood 3. Structural and nonstructural mea­ problem associated with small water­ s ures spec ially des igned to overcome the sheds. above problems need to be considered. For 3. Floods spreading out over alluvial example, land treatment to reduce sediment fans and graduarly dissipating down­ and debr is product ion in upland watersheds stream. may be part icular ly import ant. Spec ial 4. High sediment and debris content. channel construction to standardize locations of overtopping to reduce the area subject to Before evaluating these differences in inundation by a flood of a given magnitude greater detail, it is helpful to also start and to maximize utilization of the carrying with some ideas on their implications for capacity of streets, gutters, and other effective design. These include: smaller channels is another possibility. Perhaps, the urban storm runoff systems 1. A bas ic incompat ib i li ty between could be designed to convey the 10-year flood traditional structural flood control measures whereas a series of parallel streets could be which concentrate the flow in the downstream designed to carry the 100-year flood between direct ion and natural stream morphology on their curbs. As to nonstructural design, alluvial fans. Natural alluvial systems land use regulat ion to prevent development dispose of floodwater by recharge to under­ does not make economic sense where infrequent ground aquifers whereas traditional flood shallow flooding causes little damage. Flood control measures dispose of water by convey­ proof ing (Off ice of the Ch ief of Engi neers ing it downstream as is the natural pattern 1972 and Owen 1977) has its greatest advan­ in more humid climates. Structural des igns tage in this sort of situation. Older to accelerate conveyance rather than recharge buildings can be protected by short walls or are thus in basic conflict with the natural levees (Johnson 1978), and new buildings can system; and the more a design conflicts with be constructed with slightly higher floor nature, the more expensive it is to construct elevations (Federal Insurance Administrat ion and maintain. Furthermore, a more expensive 1976). Minnesota (1977) uses a special design makes little sense when flood damage manual prepared by the Corps of Engineers to per capita is less in ar id than in humid promote flood proofing in that state. climates. Designs are needed which dispose of the sediment and debr is in the upper 4. The speed with which flood waters portion of the alluvial fan, spread the water can rise in narrow mountain canyons (Sheep among drainage channels as flows move Creek 1965, Zion Canyon 1961) or mud and down a fan, and recharge as much water as debris can emerge onto alluvial fans posed possible underground. problems for flood prediction and warning system design. How does one detect isolated 2. A major problem with traditional cloudbursts in the headwaters of remote nonstructural designs appears likely in that mountain canyons and warn those downstream they are conceived in terms of regulating before the deluge arrives? How does one development on a defined 100-year floodplain maintain an effective detection and warning while not applying to areas outside that system over the many years between floods?

33 CHAPTER IV FLOOD CONTROL IN UTAH

Introduction gories: 1) information and technical advice, 2) construction of single and multiple The opening chapters presented the purpose flood contro.l projects, and 3) situation in the United States wherein emergency flood control work (U.S. Army Corps five principal decision making loci interact of Engineers 1979). in forming the de facto situation existing in local communities with respect to lives and Under the Floodplain Management Services property in danger from floods, and the third Program, established in the 1960s, the Corps chapter described hydrologic and hydraulic (on request) studies local flood problems, factors governing the hazard situation in provides information on methods of flood Utah stimulating response by the five loci damage prevention and abatement, and assists within this framework. All five loci operate . communit ies in developing floodpla in manage­ in Utah. All five are inf luenced somewhat 'ment programs. Fifteen floodplain informa­ by national norms and somewhat by local Utah tion studies have been completed in Utah. conditions. The de facto product of their These stud ies, 1 is ted in Table 5, descr ibe interactions can be expected to vary in Utah from elsewhere because the hazard s ituat ion Table 5. U.S. Army Corps of Engineers flood- is different and the perspective~ of the information studies. actors making the decisions at each locus are diffeJ;ent. The de facto product can also, however, be expected to vary from what is Stream Community Year best for Utah because of the influence of national norms. American Fork and American Fork Dry Creek and Lehi 1969 Each locus is managed in its own way. The first encompasses three separate pro­ Barton, Mill, and Bountiful, West Bountiful grams, those of the Corps of Engineers, Soil Stone Creeks and Woods- Cross 1969 Conservation Service, and Water and Power Re­ sources Service (formerly the Bureau of Blacksmith Fork and Reclamation), separately managed though Spring Creek Millville 1976 part ially coordinated through the Water Resources Council and the Pac iHc Southwest Burch Creek Ogden 1970 Inter-Agency Committee. The structural flood control programs run by city and county Box Elder Creek Brigham City 1975 engineering departments are managed indepen­ dently in every community. The third role, Farmington Bay Farmington- that of the federal flood insurance program, Tributaries Centerville 1974 is the one of the five which is managed from a single locus. The communi ty planning and Hobble Creek Springville 1973 zoning efforts of the fourth· role are separately responsible to the 29 counties and Jordan River over 100 incorporated communities. The number Complex I Salt Lake City 1969 of individuals managing floodplain property in Utah is in the thousands. The Federal Jordan River Emergency Management Agency has estimated Complex II Midvale-Draper 1974 that 26,900 structures are located on Utah floodplains (Salt Lake City Tribune, July 16, Logan River Logan 1973 1979), and many other properties suffer agricultural losses even though the buildings Ogden River Ogden 1971 are on higher ground. The overall flood hazard situation is the integrated product of Provo River and decisions at all these loci. Rock Canyon Creek Provo-Orem 1971

Federal Structural Flood Provo River and Control Measures Slate Canyon Creek Provo 1972

U.S. Army Corps of Engineers Virgin River and Washington County Fort Pierce Wash (St. George vic.) 1973 The flood control act ivit ies of the Corps of Engineers fall into three cate- Weber River Ogden 1976

35 the historical floods in the community, 1954, for flood and erosion control, develop­ outl ine present floodplain management prac­ ment of agricultural and municipal water t ices and problems, and map the boundar ies supplies, water quality, and recreation. and heights of possible (usually 100 yr and Proposed projects are initiated and co­ 500 yr) floods. The Corps is also authorized sponsored by local agencies. to conduct the flood insurance studies used to determine the actuarial flood insurance In its 1978 status report (USDA 1978) premium rates for the FEMA. the Soil Conservat ion Service reports that 50 applications involving Utah watersheds Since the 1936 Flood Control Act, the h ave been rece i ved. Of the 50 applicat ions, Corps has had responsibility for most of the 6 were canceled, 8 were terminated in the structural flood control projects of the planning stage, 18 are pending, 6 are in the federal government. As of 1979, their civil planning stage, 6 are under construction, and works program in Utah (Table 6) consisted 6 have been completed. In addition, two pi of four completed single-purpose projects lot projects (Pleasant Valley and Santaquin) (Big Wash Diversion Dam and Channel, Redmond were completed. Those projects being plan­ Channel Improvement, Jordan RiVer Channel ned, under construction, or completed are Improvement, and Kays Creek at Layton), three listed in Table 6. proposed single-purpose projects (Lower Jordan River Floodway !Parkway, Upper Jordan The distinctive component of the Soil River Project, and Coal Creek in Cedar City) Conservation Service projects is that and one author ized mult iple-purpose storage they combine the traditional structural project (Little Dell Lake). In addition, the measures of reservoir storage and channeliza­ Corps describes rules and regulations for t ion or levees with land treatment programs flood control for six multiple-purpose conceived to reduce runoff rates and particu­ storage reservoirs sponsored by the Water and lar ly sediment and debr is movement. For Power Resources Service (Echo, Rockport, Lost example, fire protection plans are formulated Creek, East Canyon, Causey, and Pineview f or forested areas, brush management and Reservoirs). Flood control operat ions are grass seeding are used for range lands, and under study for Hayes and Jordanelle Reser­ terracing is developed for cropland. Techni­ voirs in the Central Utah Project. cal assistance is provided land owners in developing appropriate land treatment, and Finally, the Corps has continuing about 30 percent of the implementation cost authority to undertake emergency flood is paid from program funds. control work, including bank protection, snagging and clearing channels, flood fight- Program Assessments , rescue, and repair. The cumulative cost o emergency work in Utah is about $1.5 The structural flood control projects of million. Cumulative expenditures by stream the three federal agencies in Utah have on are provided in Table 7. the whole been effect ive. They have func­ tioned as intended technically. Maintenance problems and adverse environmental impacts Water and Power Resources Service have been minor. The data on economic (Bureau of Reclamation) benefits already realized, from the Corps projects (Table 6) suggests that all four The Bureau of Reclamation was estab­ will far more than pay for themselves over lished in 1902 (as the Reclamation Service) the project lives. to reclaim arid western land through irr tion. The Bureau's programs have since A comparison of the projects listed in expanded t'o include municipal water supply, Table 6 with those being built in other parts hydroelectric power, recreation, water of the country would show the Utah projects quali ty, f ish and wildlife, and flood con­ to generally be small. The increasing fixed trol; and in recognition of this wider scope, cost of the federal planning process, how­ its name was changed in 1979 to the Water and ever, is making it more and more difficult Power Resources Serv ice. The proposed, for these smaller projects; the cost of in-progress, or completed projects in Utah ning is becoming disportionately large in having flood control benefits (Table 6) comparison with the benefits achieved. As ach ieve these benef its by regulat ing reser­ the federal government does less to provide voir outflows to control snowmelt runoff structural flood control, either because of following rules designed by the Corps of 'th is reason or in conformance with nat ional Engineers. Projects also provide incidental fiscal or environmental policy, a need for an flood protection from heavy summer rains increased state ro.le may appear. Before because reservoirs generally have unused activating such a program, the State of Utah storage capacity as the water surface is should develop a policy on whether and how to drawn down to supply irrigation water. obtain reimbursement from beneficiaries for project cost. Soil Conservation Service The components that seem to be needed in The Soil Conservat ion Service (SCS) a structural flood control program for Utah administers a program of small watershed include 1) watershed treatment to reduce the projects, authorized under the Watershed amount of mud and debris carried during Protection and Flood Prevention Act of cloudburst floods out of mountain canyons and

36 Table 6. Federally sponsored flood control measures in Utah.

Total Estimated Project Name Location Status Cost Annual $ Flood Benefits

I. U.S. Army Corps of Engineers Big Wash Diversion Dam and Channel Big Wash West of Milford Completed 1961 $ 343,000 125,000 Redmond Channel Improvement Sevier River near Richmond Completed 1951 1,037,000 400,000 Kays Creek at Layton Layton Completed 1972 840,000 Jordan River Improvements Salt Lake City Completed 1960 1,690,600 2,000,000 Little Dell Lake Dell Creek, East of Salt Planning Lake City Completed, Authorized 59,500,000 1,350,000 Lower Jordan River Parkway Salt Lake City Proposed, Feasibility and EIS under review Upper Jordan River Salt Lake County Study in progress Coal Creek Cedar City Feasibility studies in progress II. Water and Power Resources Service (Bureau of Reclamation) Weber River- Echo Res. Weber River 1931 2,948,104 n.a. Scofield - Scofield Res. Price River 1946 925,991 n.a. Provo River - Deer Creek Res. Provo River 1941 37,498,116 Weber Basin- 95,153,632 9,344,OOOb Rockport Res. Weber River 1957 6,687,984 n.a. Pineview Res. a Ogden River 1957 4,453,134 n.a. Causey Res. S. Fork Ogden River 1966 6,511,262 n.a. East Canyon Res. E. Canyon Creek 1966 4,772,650 n.a. Lost Creek Res. Lost Creek 1966 4,813,619 n.a. Central Utah Project- Bonneville Unit Central Utah Authorized 753,417,000 212,OOOc Hayes Res. Diamond Fork Authorized 75,000 Jordanelle Res. Provo River Authorized 100,000 Starvation Res. Duchesne River 1970 1,250 Central Utah Proj ect Upalco Uni t Taskeech Res. Lake Fork River Adv. Planning 1978 Central Utah Project- Jensen Unit 29,736,000 n.a. Tyzack Res. Big Brush Creek Under Construction 29,736,000 n.a. Central Utah Project Uintah Unit Uintah Res. Uinta River Adv. Planning n.a. n.a. 1978 Whiterocks Res. Whiterocks River Adv. Planning n.a. n.a. 1978 III. Soil Conservation Service Glenwoodd Mill Canyon- Sage Flat (1955) So. Central Sevier County Under e Construction 1,960,026 (95% complete) American Fork Dry Creek (1958) Alpine Completed 6,181,929 52,825 June 1973

apineview Reservoir completed under Ogden River Project in 1937 and enlarged under Weber Basin Project. bTotal benefits over project life. clncludes estimated annual benefits of $36,000 around Utah Lake. dOriginal application changed to a supplement of Mill Canyon-Sage Flat Watershed Project, no new flood con­ trol features. eDollars are for year following project name.

37 Table 6. Continued.

Total Estimated Project Name Location Status Cost Annual $ Flood Benefits

North Fork of Ogden River (1959) Ogden Valley Completed 807,707 12,835 Dec. 1965 (300,114) Monroe-Annabella (1963) So. Central Sevier County Under 8,377,893 23-,655 Construction (94% complete) Green's Lake Iron County near Cedar Completed 335,420 n.a. City Apr. 1962 Blue Creek - Howell (1972) North Box Elder County Under 5,786,985 123,935 Construction (98% complete) Miller-Bigelow (1960) Juab County near Nephi Completed 269,081 12,400 June 1964 Minersville Beaver County around Completed 5,311,376 33,900 Minersville Sept. 1968 Warner Draw (1968) Washington County around Under 9,101,189 152,780 St. George Construction (86% complete) Ferron (1962) Emery and Sanpete Counties Under 10,015,749 52,045 Construction (94% complete) Muddy Creek So. West Emery County Planning n.a. n.a. Clarkston Creek No. West Cache County Planning n.a. n.a. Vernon (1967) So. East Tooele County Completed 1,849,762 4,430 Sept. 1976 Hansel Valley (1975) No. Central Box Elder Under 1,176,331 87,750 County Construction (51% complete) Martin Lateral Duchesne County near Roosevelt Planning n.a. n.a. Hancock Cove Duchesne County near Roosevelt Planning n.a. n.a. Class K-2 Duchesne County near Roosevelt Planning n.a. n.a. T.N. Dodd Irr. Company Duchesne County near Neola Planning n.a. n.a. Pleasant Creek (1956) E. Central Sanpete County Completed 560,711 17,060 Santaquin Canyon (1954) South Utah County around Completed 220,495 4,300 Santaquin

fUSDA, SCS. 1978. Status of watersheds in Utah, Salt Lake City. October. onto alluvial fans, 2) conveyance systems to crops, irrigation systems, and rural roads. transport flood waters origlnating in these Furthermore, the SCS can combine flood small canyon watersheds through developed control features in projects that also areas, 3) levees to protect low-lying areas, serve other water resources management and 4) storage reservoirs to contain snowmelt purposes and thereby enhance the probability floods on the larger streams and rivers. of project economic feasibility. Water In the rural areas of the state, the SCS supply and recreation benefits can, for watershed protect ion program is well suited example, be added to the flood control because 1) much of the problem is caused by benefits. mud and debr is flows that are best con­ trolled by watershed treatment, 2) the The small projects' program of the Corps problems largely originate from small water­ of Engineers focuses on urban areas where sheds within the size limitations for the sma 11 levees or channelizat ion are the most SCS program, and 3) most of the damage is to economic structural approach. Utah rivers in

38 Tabie 7. Emergency work--Corps of Engineers. additional flood control storage is clouded by the fact that most of the relat ively few technically feasible sites for the purpose in the state have already been exploited and Stream Costs the increased concern over adverse impacts on Basin environmental quality. Nevertheless, several points are important in assessing the future Great Salt Lake $ 749,000 role of flood control storage in Utah. Weber & Ogden Rivers 107,800 American Fork River 65,000 1. The larger multiple-purpose projects Hobble Creek 83,400 provide protection on riverine floodplains Provo River 124,500 but do nothing to control flooding from Spanish Fork River 64,400 smaller canyons. Single-purpose structures Salt Creek 43,600 are required to control flooding from these Tributaries to Jordan River 8,700 tributaries (only recreation offers oppor­ Jordan River 104,400 tunit ies for dual-purpose development), and Big and Little Cottonwood this need is relatively more important for Creeks 17,200 Utah because flooding from small streams Logan River / 52,000 causes such a large small percentage of the Peteetneet Creek 78,000 total damage. Sevier Lake Basin 278,000 2. One scenario for future water Sevier RiVer and Chicken resources management in Utah is that the Creek 51,000 federal government will withdraw from its Shoal Creek 40,400 role of water development for urban and Pinto Creek 40,900 agr icultural uses and that future water Coal Creek 39,800 supply projects will be built more and more Cedar Creek 67,100 by state government. As the state undertakes Red Creek 8,300 water supply project construction, the Salina Creek 30,000 opportunities for dual use for flood control should be reviewed for each new project and Green River Basin 319,000 flood control storage should be included when Duchesne River 72,000 justified. Nonfederal projects in other White River 48,000 states have received Corps' financial assis­ Ashley Creek 186,000 tance in paying for the flood control fea­ Uinta & Whiterocks Rivers 13 ,000 tures, and this funding source should be considered. Colorado-San Juan 214,000 Basin (Breakdown 3. Even though existing reservoirs with by stream not flood control storage have a prescribed available) operat ing procedure for joint use of the space, possibilities for increasing total Source: U.S. Army Corps of Enginers benefits by using either more or less of the existing storage for flood control will develop in the future. Each situation needs to be periodically reviewed so that necessary urban areas are relatively small, and most reauthorization adjustments can be made can easily be contained by projects of this (Holley and Kane 1974). size in areas where the SCS program is less appl icable because the benef its are From the point of view of gett.ing a to urban property. Small levees are by problem corrected quickly, local InItIatIve nature single purpose flood control struc­ is preferable because, except in emergencies, tures, and thus there is no opportunity to the federal implementat ion process is very enhance their economic feasibility through slow. Nevertheless, the flood hazard area mult ipurpose projects. One gap between the may not be contained within the boundaries of two programs is in the need for watershed a single locality, thus creating a role for treatment to reduce mud and debris flow onto a larger jurisdictional authority--state or purely urban floodplains. The SCS has the federal--to coordinate local efforts. expert ise for th is sort of des ign but is limited financially in the role it can take The comprehensive framework studies in urban flood control. (Water Resources Council 1971a, 1971b, 1971c) project future expansion for the Since cloudburst meteorological events federal structural flood control program. cover relatively small geographical areas, The Upper Colorado study (WRC 1971b) project they are only an important cause of flooding ed an increase in average annual flood on smaller watersheds. For larger water­ damages in the basin from $2.8 to $10.5 sheds, half or more of the total annual million over the period from 1965 to 2020 and precipitation can accumulate in the winter an increase in residential and commercial snowpack, melt in the spring, and cause major damages with in this total from $450,000 to snowmelt flooding. A number of reservoirs $2,740,000. This latter increase is based on have already been constructed to store these assumptions of normal increases in population f lows (Table 6), but the construct ion of and economic activity and that no floodplain

39 development will be induced by structural reduces storm runoff flows to about 10 flood control. To cope with these increases, percent of their peak values, thus greatly the study projects future needs for a number reducing the size required and cost of of flood control reservoirs, levees, and conveyance facilities. Detention basins channels. The Soil Conservat ion Service also may serve mult iple purposes, includ ing projects watershed management and land recreation, beautification, and flood treatment needs. control. Cit and Count Structural The clustering of numerous CItIes, large Foodt Contro t Measures and small, on the foothills and lower, flatter areas along the Wasatch Front makes The authority of Utah communities to it difficult, if not impossible, for indi­ deal with flood problems lies in Chapter 8, vidual cities to solve their urban runoff "Flood Control Projects and Drought Emer­ problems independently. Actions by uphill gencies," of the Utah code. Section 17-8-1 cities create problems for adjoining cities provides the county commissioners authority and farms downhill. For example, a new drain to contract with federal agencies to con­ system constructed to the boundary of an struct flood control projects. Section upland city will discharge flood flows into 17-8-2 provides authority to use county funds the downhill city and may result in property to pay the nonfederal costs of such projects damage, poor relations between the cities, including those for maintenance and rights­ and law suits. In this setting, the planning of-way. Section 17-8-5 provides authority to of urban runoff systems must be coordinated clean natural channels and construct new or on at least a county-wide basis to be ef­ enlarged ones. Counties have eminent domain fective. This has been recognized by and have to conform to the pollution control public officials, and county master plans for standards of the health authorities and the storm water systems have been prepared. fish and game commission. Davis County has established a two mill levy to implement its plan by financing flood Most of the cities and towns in the control improvements. The funds generated, metropolitan area along the Wasatch Front current ly $ 500,000 per year, are used pr i­ have a rectangular street pattern with the marily for constructing trunk lines to convey north-south streets generally parallel to the runoff to the Great Salt Lake. contours and the east-west streets sloping downhill at gradients that are generally The National Flood Insurance Program quite steep close to the mountains and flatten gradually toward the west. These Program History streets are built lower than the adjacent buildings and serve as important flood-runoff The National Flood Insurance Act of 1968 conveyance facilities. The storm runoff from (P.L. 90-448) made flood insurance available the streets and adjacent lots flows down the for the first time to property owners in gutters. Gutter flow is somet imes diverted coastal and riverine flood hazard areas. The at drop inlets into storm sewers or open idea of a national flood insurance program ditches and conveyed downstream. was proposed by ~resident Truman in 1951, but Congress was leery of the possible federal The larger cities along the Wasatch expense and refused to support the proposal. Front--Ogden, Bountiful, Salt Lake City, Extensive flooding in 1955 increased public and Provo--all have storm drainage programs. support. Early in 1956, President Eisenhower BUr ied culverts were installed beginning in proposed a 5-year flood insurance program, the late l800s to route streams through urban wh ich Congress passed virtually intact. areas. Until the late 1960s, storm drainage The program enacted in the Flood Insurance plans were based mainly on the concept of Act of 1956, however, died a quiet death providing pipeline capacity to carry peak when Congress failed to appropriate funds for flows; but because of the tremendous cost of its implementation. A decade later, in such an approach, only a few large diameter response to continued increases in the cost storm drains were constructed. In 1974, the of federal disaster relief, the newly formed Ogden City Council passed an ordinance Department of Housing and Urban Development requiring all developers of land areas (HUD) formulated a new vers ion of the flood exceed ing 30,000 square feet to provide insurance idea wh ich was passed by Congress holding basins to contain any increase in the and signed by President Johnson into law on runoff peaks caused by the construction. Aug us t 1, 1968 • Sumps or other storage areas are now used to collect runoff peaks and thereby reduce the The main feature which the 1968 Act size requirements and hence the cost of the added to the program conceived 12 years conveyance facilities (Hoggan and Nielson earlier was to condit ion the eligibility of 1979) . individuals for flood insurance on their community having an acceptable floodplain management program. While community partici­ The detent ion storage concept was pation in the National Flood Insurance introduced as a superior economic alternative Program was strictly voluntary, individuals to pipelines for controlling cloudburst could not purchase insurance unless the runoff in this area in 1969 (Nielsen and community (incorporated city or county for Maxwell 1969). Temporary detention storage unincorporated areas) in which their property

40 was located, joined the program. Th is re­ the stronger provision. The addition of this qui red ord i nances controll ing f loodpla in financial "stick" to the subsidized insurance development. The program thereby paired "carrot" stimulated rapid expansion in the eligibility for flood insurance with imple­ program and marked the beginning of partici­ mentatIon of a nonstructural flood control pation by Utah communities. By the end program to reduce future losses so that the of 1975, two years after passage of the 1973 insurance program cost could be justified by Act, community membership had risen to almost future decreases in federal expenditures 13,000 nationwide (most in the emergency for flood damage relief and structural flood phase) with over 625,000 policies in force control programs. (Platt 1976, p. 305). Growth in the insurance program was slow Community Requirements for the first several years. In the first and Program Coverage year, only four communit ies became eligible nationwide and only 20 policies (Platt 1976, Under the 1968 Act, flood insurance p. 304) were written. By 1972, these numbers would be made available in a community had grown to 3,000 and 90,000 respectively after a detailed study had been completed but still covered only a small portion of the indicating flood prone areas by degree of 16,000 flood-prone communities and 6.4 risk and the community had enacted the million residences in flood-prone areas. necessary land use regulations to control floodplain development. Since FIA did not Part of the problem was that the com­ have the manpower or funds to conduct de­ munities lacked information on flood hazard tailed risk studies quickly enough to respond and floodplain boundaries. This information to the communities that had otherwise ful­ proved more costly to obtain than had pre­ filled the requirements of membership, the viously been anticipated, and the federal regular program, wherein premiums are actu­ budget to perform the necessary studies was arial in that they are based on the degree of not able to keep pace with the requests by exposure to flood hazard, was supplemented in ~ommunities to enter the program. To al­ 1969 by an emergency program, wherein pre­ leviate this problem, a temporary emergency miums are at a uniform rate. Presently, phase of the program was added in 1969. both the emergency and regular programs have Commun it ies could jo in by submi t t ing an two phases (Table 8), determined by the application to HUD's Federal Insurance amount of flood hazard information provided Administration (FIA) with evidence that a the community by FlA. (C.F.R. Title 24, Ch. building code and floodplain regulation 10, Subchapter B, Section 1910.3.) ordinance had been enacted. After FIA finished its study of the community's flood In the first phase of the emergency haz;3rd (FIS), the community could convert program, the FIA does not provide information from the emergency to the regular program. defining community flood hazard areas. Instead, the community takes the initiative, The entry of new communities into the identifies the hazards, and presents evidence program was also slowed because so few to FIA of ordinances establishing a system of' community officials acted until their com­ building permits and zoning controls. munity suffered a flood event. A cut The ordinances should provide for the review in the premium rate made possible by in­ of building permit applications and sub­ creased subsidization in June 1972, coupled division proposals to discourage the con­ with the damage caused by Hurricane Agnes struction of new facilities in flood hazard about the same time, stimulated a jump in areas or when construction occurs, encourage participation. Furthermore, the Nixon use of flood resistant methods and materials. Administration decided that stronger measures were needed to prevent flood disaster relief The second phase of the emergency from becoming excessively costly. The result program is entered after the FIA has identi­ was the Flood Disaster Protection Act of fied special flood hazard areas (A zones, or 1973 (P.L. 93-234), which provided that no the limits of the 100 year flood) by pub­ federally related financial assistance lication of a Flood Hazard Boundary Map would be available to help the owners of (FHBM). Once the FHBM has been published, flood damaged property unless the applicant the community must enter the program or else had purchased flood insurance. No loans from proposed development in the hazard areas federally secured financial institutions cannot be financed by federally secured could be obtained 'for new construction. financial institutions. The first phase of Since individuals can buy flood insurance the regular program is entered once water only if their community is a program member, sur face levels are def ined, and the second community participation became a condition of phase of the regular program also requires individuals securing federal fiancial that a floodway be established and protected assistance for flood relief. The financing against manmade constrictions that would add prohibition for individuals in non--member to flood depths by creat ing backwater. The flood-prone communities was softened to a FIA requirements for the regulatory programs notification requirement by the Housing of the communities in each phase are given in and Community Development Act of 1977 (P.L. Table 8. 95-128); however, the Water Resources Council (1978) interpretation of Executive In late 1979, FEMA inaugurated a special Order 11988 appears to have re-established conversion and map rescission effort to

41 Table 8. Phases of participation in the Flood Insurance Program.

Phase Information Provided by FIA Community Floodplain Ordinance Requirements

Emergency a) No FIA defined special flood Require permits for all proposed construction and develop­ hazard area; no water surface ment; require flood resistant materials and methods for elevation data; insufficient new construction in flood prone areas; review proposed information to identify floodway. developments to assure that all required state and federal permits are obtained; review proposals for subdivisions in flood prone areas to assure that flood damage will be minimized, adequate drainage will be provided, and utili­ ties will be constructed to minimize flood damage. b) FIA designated areas of special Require permits, review proposals, and establish standards, flood hazard (FHBM); no water as above, in A (IOO-year floodplain) zones; make reasonable surface elevation data nor flood­ effort to obtain water surface elevation data and elevation way identification of lowest habitable floor for new construction in A zones; assure that new development does not reduce flood carrying capacity; require anchoring of mobile homes, and mobile home park evacuation plan in A-zones, notify adjacent com­ munities and the State Coordinating Officer prior to alteration of stream course. Regular c) Water surface elevation data for Require permits and standards as in b) above; require AI-A30 zones, and appropriate AO elevation to base flood level of lowest habitable floor and A99 zones (FIRM); no regulatory for new construction and substantial improvements (non­ floodway identified residential structures may be floodproofed instead if certified), require elevation of mobile homes to base flood level; prohibit new development in AI-A30 zones that would raise flood elevations one foot or more. d) Water surface elevation data for All requirements of c); establish regulatory floodway and AI-A30 zones, and appropriate AO prohibit development in it that would increase flood and A99 zones (FIRM); regulatory levels; prohibit placement of mobile homes in regulatory floodway identified floodway or AI-A30 zones except in eXisting mobile home parks. address the problems of small communities enroll, the maps were rescinded for 4 non­ where some floodplain management effort and members, and 4 members were put on the the establishment of eligibility to purchase priority list for detailed study (Karcher ftood insurance may be justified even though 1979) • the cost of a detailed study is not. The FEMA options for dealing with participating The insurance covers losses due to communities were 1) special conversion to the flooding of residential and commercial regular program based on a revised map structures and their contents but not damage containing only unnumbered A and C zones with to landscaping or any items outs ide the residential insurance rates in the A zone of building when the flood hits. All policies from 10 to 20 cents per $100 and in the C carry a $200 deductible provision. Flood zone of from I to 15 cents (suggesting a losses are def ined to include damages sus­ realization that that hazard may not be much tained as a result of a general flood con­ different between the zones, 2) special dition as long as the causes of flooding are conversion to the reguliH program without a not primarily located on the insured's map placing the entire community on C zone property. Thus, damages to structures caused rates, or 3) placing the community on a by flooding from dam failure, such as that in priority list for detailed study. Options Payson in 1972, would be covered. But for dealing with nonparticipating communities flooding from breaches in irrigation canals were 1) rescind the map so the community would be covered only if caused by heavy rain could join the program with C zone rates or snowmelt. applicable throughout or 2) encourage the community to enroll. The criteria The amounts of flood insurance available for conversion without a map were that the are listed in Table 9. During the emergency flooding 1) be confined to a floodplain less phase, all those who purchase policies in a than 200-feet wide, 2) be from a source community are charged the same rate. In the area smaller than 1.0 square mile, or 3) regular phase, the lower subsidized rates are result solely from backwater from a manmade continued for structures built before the structure. Of the 30 Utah communities program came into effect but actuarial rates examined in November and December 1979, 15 are charged as estimated to represent average members were recommended for special con­ annual damages to newer construction. Three version with a map. 7 nonmembers were zones are defined. The A zone encompases the recommended for special conversion when they entire IOO-year floodplain. It is divided

42 Table 9. Maximum amounts of insurance available.

Emergency Program Regular Program Type

1st LayerC Premium 2nd LayerC Premium Total

Structures Single family residential $ 35,000a $.25/$100 $150,000 actuarial $185,000 Other residential 100,000b $.25/$100 150,000 actuarial 250,000 Small business 100,000 $.40/$100 150,000 actuarial 250,000 Churches & other property 100,000 $.40/$100 100,000 actuarial 200,000

Contents Resident ial 10,000 $.35/$100 50,000 actuarial 60,000 Small business 100,000 $.75/$100 200,000 actuarial 300,000 Churches & other property 100,000 $.75/$100 100,000 actuarial 200,000

Source: FIA, Federal Register, 43 (Jan. 17, 1978);2572. a$50,000 in Hawaii, Alaska, Guam, U.S. Virgin Islands. b$150,000 in Hawaii, Alaska, Guam, U.S. Virgin Islands. cA property owner is entitled to buy a first layer of insurance to the maximum amount indicated and for the premium shown when his community enters the emergency program. When the communi~y enters the :egular program, he can purchase additional or "second layer" insurance to the total shown by pay1ng the actuarial rate determined by the hazard at his building site.

into subzones according to a flood hazard residents are not eligible to buy flood factor equalling the difference in elevation insurance. When a community is suspended, no between the 10-year and 100 year water new insurance can be sold nor old policies surfaces, a concept often hard to apply in renewed, but paid policies are honored until Utah where the large floods are often not any they exp ire. Since policies are sold on an deeper, instead they spread over ~ larger annual basis, no flood insurance will still area. Insurance premiums are set from the A be in effect a year after a community's subzone number and the elevation of the main suspension. floor in the building and can go as high as $25/$100 in the areas of highest risk. The B Statewide, 2676 policies were in force zone encompasses areas outside the 100-year at the end of May covering almost 10 percent floodplain but within the 500-year flood­ of the 26,900 structures estimated to be on plain, and premiums are in the range of $0.03 Utah floodplains. Coverage totals $86,187,800 to $0.30 per $100. The C zone encompas ses or an average of $32,200, per structure. At areas outside the 500-year floodplain, and the end of July, the figures were 2714 property owners there can purchase insurance policies for a total coverage of $89,329,000. for between $0.01/$100 and $0.25/$100, depending on the characteristics of their Of the 89 communities (81 municipalities structure. Property owners in the Band C and 8 count ies) where res idents are not zones would be purchasing protection against el ible to buy flood insurance, 40 (the 3 rarer events and security in case the suspended communities plus 37 others that flood risk areas have not been mapped cor­ have not joined the program even though the rectly. Policies are written by private hazard area within them has been defined) are insurance agents for the federal government. also subject to the provisions of the regula­ Premiums, less da set fee for the insurance tory program that prevent federally supported agent, are paid into a special fund created f inane ial inst itut ions from mak ing loans under the Act for payment of claims. on floodplain property. The other 49 are not subject to these sanctions because specific Community Floodplain Management Programs flood prone areas have not been identified. The current (May 31, 1979) status in the Table 11 summarizes the status of the Nat ional Flood Insurance Program of each of communities by code classification. One can the 29 counties and 222 incorporated munici­ see from the summary that since the more palities in Utah is shown in Table 10. populous communities have qualified for the Of these 251 communities, 15 are in the progr am, 92.6 percent of the populat ion of regular program, 147 are in the emergency the state are eligible to buy flood insurance program, 3 were once in the emergency program and only 0.58 percent live in communities but have since been suspended, and 86 have where loan sanctions apply. Since the 86 never been in the program and hence their communities where property owners are not

43 Table 10. and flood insurance participation of Utah counties and incorporated towns.

Flood Insurance Program Participation (5/31/79)

Community Population Date of Hazard Policies Amount of Name (1975 Est.) Code 3 Entry Identified in Force Insurance

Counties (Unincorpor­ ated areas)

Beaver 604 05/34/75 2 $ 62,000 Box Elder 5,138 12/17/74 02/28/78 & 1 17,000 01/30/79 Cache 2,699 4 Carbon 4,409 1 11/27/74 06/14/77 4 60,500 Daggett 431 4 Davis 10,740 1 04/22/75 02/07/78 5 155,800 Duchesne 5,966 4 Emery 1,333 1 07/25/75 01/17/78 8,000 Garfield 284 1 07/03/75 01/10/78 Grand 1,741 4 Iron 1,722 1 05/08/75 04/11/78 4 204,600 Juab 481 4 Kane 526 1 07/01/75 01/10/78 2 115,500 Millard 1,930 4 Morgan 2,736 06/25/75 10/18/74 & 5 223,500 02/ 14/78 Piute 190 1 03/14/78 11/08/77 33,000 Rich 532 4 Salt Lake 273,019 1 09/26/74 08/30/77 64 2,082,100 San Juan 7,320 1 06/39/75 01/31/78 Sanpete 996 1 03/02/76 11/14/78 Sevier 1,126 1 11/14/75 02/07/78 Summit 2,423 1 06/10/75 01/03/78 4 $ 113,000 Tooele 4,247 06/07/76 Uintah 12,145 11/30/77 02/14/75 35,000 10/18/77 08/15/78 Utah 15,926 1 11/12/71 01/10/75 7 158,000 Wasatch 1,616 1 04/04/75 05/31/77 70,000 12/13/77 2 70,000 Washington 2,087 1 10/15/75 02/07/78 7 278,000 Wayne 974 4 Weber 11,867 03/25/75 05/02/78 14 601,100

Cities & Towns

Alpine 1,524 1R 02/11/76 2 67,000 Alta 226 5 Altamont 249 5 Alton 41 02/05/79 Amalga 207 SC 03/03/75 09/05/75 American Fork 10,467 OS/23/74 12/28/73 & 40 $ 1,307,600 02/06/76 Annabella 303 1 04/14/76 01/10/75 35 1,088,800 Antimony 126 3 04/02/76 Aurora 657 1 01/26/76 01/31/75 & 6 191,300 01/07/77 Austin n.a. 4 Bear River City 473 3 SC 09/05/75 Beaver 1,750 3 06/11/74 Bicknell 282 1 07/10/75 01/24/75 7 191,300

aCodes are defined in Table 11. TWo-letter designations after code are FEMA recommended actions in December 1979 SC - Special conversion to regular program (contingent on community enrollment) DS - Detailed study RM - Rescind map

44 Table 10. Continued.

Flood lnsurllnce Program Participation ( 5/31/79)

Community Population Date of Hazard Policies Amount of Name (1975 Est.) Cod'i!a Entry Ident ified in Force Insllrance

Cities & Towns (Cont. )

Blanding 2,768 4 Bloomington n,a. 4 Boulder 148 5 Bountiful 30,358 lR 09/29/78 10/26/73 47 1,377,800 Brian Head 118 5 Brigham City 14,157 ~ 11/01/74 06/07/74 & 33 1,417,900 01/16/76 Cannonville 123 5 Castle Dale 861 1 07/25/75 01/10/78 35,000 Castle Gate n.a. 4 Cedar City 10,349 1 03/19/75 01/23/74 & 32 1,024,000 03/05/76 Cedar Fort 241 1 01/06/76 02/07/75 2 $ 64,000 Centerfield 485 4 Centerville 5,198 1 07/24/75 06/28/74 & 6 282,000 03/19/76 Charleston 217 10/22/75 09/19/75 2 60,000 Ci rclevi lle 435 P9/14/77 08/02/74 & 05/11/76 Clarkston 471 SC 09/23/76 09/05/75 Clearfield 13 ,416 lR 02/20/79 08/02/74 & 10 345,000 10/01/76 Cleveland 315 3 07/12/77 Clinton 3,629 1R 07/21/78 08/02/74 & 17 465,000 04/30/76 Coalville 820 08/02/74 & 4 94,000 10/03/75 Corinne 486 1 SC P9/28/77 06/25/76 Cornish 152 3 SC 04/02/76 Delta 2,016 1 OS/20/7 5 07/25/75 2 43,.500 Deweyvi lIe 236 3 04/29/77 Duchesne 2,198 1 11/25/74 06/21/74 & 37 1,158,500 10/24/75 East Carbon 2,168 1 03/07/75 10/29/76 1 35,000 East Layton 876 1 10/17/74 06/28/74 & 2 $ 70,000 04/01/77 Elmo 176 5 Eis inore 431 1 09/26/75 11/14/75 19 471,900 Elwood 323 3 01/24/75 Emery 219 lR 09/11/78 02/07/75 4 127,100 Enoch 133 Enterprise 1,216 3 08/16/74 Ephraim 2,380 1 01/31/75 06/28/74 & 7 145,000 01/16/76 Escalante 654 ()4/22/75 08/09/74 & 1:/28/75 Eureka 732 07/02/75 06/07/74 & 5 68,700 11/07/75 Fairview 800 06/12/75 06/28/74 & 12 238.,400 01/09/76 Farmington 3,372 05/13/75 06/28/74 & 7 209,500 10/31/75 Fayette 85 5 Ferron 756 1 01/20/75 OS/24/74 & 12/26/75 Fielding 301 3 RM 08/08/75

aCodes are defined in Table 11. Two-letter designations after code are FEMA recommended actions in December 1979 SC - Special conversion to regular program (contingent on community enrollment) DS - Detailed study RM - Rescind map

45 Table 10. Continued.

Flood Insurance Program Participation (5/31/79)

Community Population Date of Hazard Policies Amount of Name (1975 Est.) Codea Entry Identified in Force Insurance

Cities & Towns (Cont.)

Fillmore 1,826 05/01/75 06/28/74 & 2 $ 65,800 05/14/76 Fountain Green 457 3 04/02/76 Francis 328 3 07/25/75 Fruit Heights 2,001 1 05/11/77 03/18/77 35,000 Garden City 149 5 Garland 1,165 5 Genola 542 3 02/07/75 Glendale 257 1 05/19/77 04/02/76 Glenwood 294 1 07/l0/77 10/22/76 5 151,200 Goshen 473 3 02/07/75 & 04/15/77 Grantsville 3,657 1 07/09/75 5 147,100 Green River 968 1 06/21/75 & 3 105,000 12/05/74 Gunlock 4 Gunnison 1,193 1 08/27/75 08/16/74 & 30,000 08/13/76 Harrisville 757 09/29/75 08/08/75 2 70,000 Hatch 128 08/05/75 02/07/75 & lO/10/75 Heber City 3,633 03/25/75 15 497,500 Helper 2,198 2S 01/09/74 & 11 $ 342,000 01/23/76 Henefer 446 SC 07/23/75 02/21/75 & 04/23/76 Henrieville 166 1 02/07/75 02/07/75 Hiawatha 166 5 Hildale 729 3 06/04/76 Hinckley 436 4 Holden 356 1 09/28/77 06/03/77 I 35,000 Honeyville 716 1 SC 03/10/76 06/28/74 & 01/02/76 Howell 163 5 Huntington 1,303 1 07/09/75 OS/24/74 Huntsville 609 3 RM 06/21/74 Hurricane 1,725 1 08/05/75 07/12/77 1 45,000 Hyde Park 1,309 1 SC 03/10/75 08/02/74 & 1 35,000 12/19/75 Hyrum 3,137 SC 11/07/74 OS/24/74 & 04/09/76 Ivins 240 1 .10/21/74 09/12/75 7 220,000 Joseph 141 1 03/23/76 01/10/75 4 $ 91,500 Junction 158 1 01/07/75 08/08/75 1 32,500 Kamas 849 1 07/02/75 08/16/74 & 6 184,000 07/30/76 Kanab 2,088 3 10/29/76 Kanarravi lIe 263 1 06/06/75 12/17/76 2 48,900 Kanosh 328 1 11/25/77 04/02/76 2 60,400 Kaysville 7,553 1 04/18/75 06/28/74 & 9 371,100 K'i'nilworth 09[03/76 K~ngston 139 3 02/04777 Kooshar.em 127 3 12/24/76

aCodes are defined in Table 11. Two-letter designations after code are FEMA recommended actions in December 1979 SC - Special conversion to regular program (contingent on community enrollment) DS - Detailed study RM - Rescind map

46 --. Table 10. Continued.

Flood Insurance Program Participation (5/31/79)

Community Population Date of Hazard Policies Amount of Name (1975 Est.) Code a Entry Identified in Force Insurance

Cities & Towns (Cont.)

Laketown 217 3 SC 11/12/76 La Verkin 785 1 09/03/75 07/02/76 Layton 15,411 1 12/13/74 08/09/74 & 103 3,431,600 05/14/76 Leamington 104 5 Leeds 224 1 08/11/78 04/02/76 Lehi 5,736 1 10/18/74 02/07/75 11 327,200 Levan 402 1 08/01/78 06/21/77 1 35,000 Lewiston 1,332 1 SC 06/29/76 08/16/74 & 12/19/75 Lindon 2,083 3 06/21/77 Loa 341 3 12/20/74 Logan 23,810 1 11/26/74 01/16/74 & 24 $ 791,700 04/08/77 Lynndyl 105 5 Maeser n.a. 4 Manila 345 5 Manti 1,869 1 07/10/75 08/09/74 & 45 1,232,400 12/19/75 Mantua 426 SC 08/20/75 01/17/75 Mapleton 2,727 05/07/75 06/28/74 & 03/26/76 Marysvale 325 1 03/08/77 02/11/77 4 85,000 May field 295 3 OS/28/76 Meadow 252 3 07/02/76 Mendon 511 1 SC 08/04/76 07/18/75 & 04/01/77 Midvale 8,310 12/09/76 09/26/75 2 42,300 Midway 977 09/11/75 06/28/74 & 1 11,100 10/31/75 Milford 1,283 02/24/75 08/09/74 & 12/19/75 "':'j Millville 549 3 SC 10/22/76 Minersvi lIe 449 4 ;., . Moab 4,500 1 09/17/74 06/21/74 & 81 $ 2,787,400 12/26/75 Mona 450 3 06/21/77 Monroe 1,235 07/08/75 06/28/74 & 13 362,600 10/03/75 Monticello 1,726 3 12/24/76 Morgan City 1,704 11/26/74 06/28/74 & 41 1,258,700 04/16/76 Moroni 886 07/09/75 09/06/74 1 22,000 Mount Pleasant 1,743 02/25/75 07/11/75 31 719,000 Murray 22,595 12/19/74 03/29/74 & 20 786,100 12/19/75 Myton 446 3 04/02/76 Nephi 2,882 1 OS/29/75 Newton 501 SC 1 11/15/76 07/ 11/75 Nib1ey 419 DS 1 03/24/75 07/18/75 North Logan 1,497 DS 1 09/26/74 06/28/74 & 11/21./75 North Ogden 6,566 1 10/02/75 05/06/77 24 786,000 North Salt Lake 3,092 1R 08/29/78 06/28/74 & 6 209,000 08/13/76

aCodes are defined in Table 11. Two-letter designations after code are FEMA recommended actions in December 1979 SC - Special conversion to regular program (contingent on community enrollment) DS - Detailed study RM - Rescind map 47 Table 10. Continued.

Flood Insurance Program Participation (5/31/79)

Community Population Date of Hazard Policies Amount of Name (1975 Est.) Codea Entry Identified in Force Insurance

Cities & Towns (Cont.)

Oak City 302 1 09/22/75 02/07/75 3 $ 78,000 Oakley 294 1 06/11/75 01/31/75 & 4 101,400 12/24/76 Ogden 68,978 12/27/74 06/21/74 & 35 1,165,100 08/16/77 Onaqui 443 4 Ophir 85 4 Orangeville 655 lR 03/01/79 06/07/74 & 1 8,500 12/12/75 Orderville 472 3 03/15/78 02/04/77 Orem 35,584 1 03/15/78 10/29/76 6 173,000 Panguitch 1,314 1 03/10/75 06/28/74 1 19,400 Paradise 487 3 RM 10/04/74 11/05/76 Paragonah 260 1 03/12/75 02/14/75 2 54,100 Park City 1,559 1 05/08/75 09/06/74 12 457,900 09/03/76 Parowan 1,764 06/09/75 08/16/74 & 5 145,800 12/19/75 Payson 6,500 2S 06/28/74 & 21 559,800 12/05/75 Perry 1,038 SC 02/07/78 07/26/74 & 11/28/75 Pickelville 120 5 Plain City 1,916 1 02/07/78 06/03/77 '1. $ 70,000 Pleasant Grove 7,074 1 08/05/75 2 76,000 Pleasant View 2,312 1 07/23/75 09/24/76 29 1,031,000 Plymouth 187 3 RM 08/22/75 Portage 196 5 Price 7,391 lR 03/01/79 01/16/74 & 75 2,257,600 11/28/75 Providence 2,293 1 DS 05/02/75 08/13/76 1 35,000 Provo 55,593 1R 02/01/79 02/15/74 & 62 1,755,200 06/04/76 Randolf 507 3 SC 08/16/74 Redmond 459 1 07/02/75 Richfield 4,947 1 09/26/74 OS/24/74 & 29 926,200 12/05/75 Richmond 1,317 1 SC 06/10/75 04/02/76 Riverdale 4,707 1 10/04/74 06/28/74 & 30 958,300 11/28/75 River Heights 954 4 Riverton 3,442 1 10/23/75 11/01/74 41 1,271,900 07/23/76 Rockville n.a. 4 Roosevelt 3,943 5 Roy 16,781 lR 10/24/78 02/07/75 24 780,900 Rush Valley 541 3 10/25/77 Salem 1,480 1 01/20/75 06/28/74 2 65,000 Salina 1,685 1 04/30/74 01/23/74 & 22 $ 612,000 09/26/75 Salt Lake City 169,917 1 OS/28/74 12/27/74 992 33,190,200 Sandy 10,077 1 02/03/75 07/26/74 & 32 951,900 01/16/76 Santaquin 1,529 05/16/75

aCodes are defined in Table 11. Two-letter designations after code are FEMA recommended actions in December 1979. SC - Special conversion to regular program

48 ...... " Table 10. Continued .

Flood Insurance Program Participation (5/31/79)

Community Population Date of Hazard Policies Amount of Name (1975 Est.) Code a Entry Identified in Force Insurance

Cities & Towns (Cont.)

Santa Clara 383 1 08/07/75 06/04/76 Scipio 223 1 08/03/78 07/12/77 Scofield 49 5 Sigurd 358 1 09/26/75 09/19/75 Smi thfie1d 4,280 1 12/ 18/74 06/28/74 & 6 145,000 12/26/75 Snowville 170 5 Soldier Summit 10 5 South Jordan 4,098 1 06/10/75 07/26/74 6 187,000 01/30/76 South Ogden 10,175 1 08/02/74 04/05/74 4 98,000 South Salt Lake 9,041 1 OS/23/75 09/19/75 2 47,000 South Weber 1,265 lR 09/12/78 06/28/74 & 02/13/76 Spanish Fork 8,065 4 Spring City 591 1 05/07/76 06/27/75 1 $ 33,000 Springdale 249 3 05/10/77 Springvi lIe 10,206 2S 02/01/74 & 53 1,496,600 OS/21/76 St. George 8,760 1 08/28/74 08/16/74 & 38 1,192,700 06/11/76 & 11/22/77 St. John-Clover n.a. 4 Sterling 127 5 Stockton 403 1 03/23/76 01/24/75 1 20,000 Sunnyside 517 IR 09/29/78 04/02/76 3 63,000 Sunset 6,300 lR 11/21/78 06/28/74 & 4 136,600 02/13/76 Syracuse 2,991 lR 06/01/78 06/28/74 7 251,000 Tabiona 235 4 Tooele 12,905 1 03/10/75 08/16/74 & 50 1,361,800 04/09/76 Toquerville 292 3 06/25/76 Torrey 104 1 03/22/79 11/12/76 Tremonton 2,981 3 SC 04/23/76 Trenton 390 3 SC 06/27/75 Tropic 359 1 09/03/75 02/07/75 26,000 Uintah 381 1 11/30/77 10/29/76 1 35,000 Vernal 5,492 1 04/16/75 07/03/76 8 215,200 Vernon 180 3 06/04/76 Virgin 101 I 06/25/75 06/25/76 wales 121 4 Wallsburg 265 3 07/02/76 Washington 1,245 1 07/07/75 08/02/74 & 7 $ 278,000 06/04/76 Washington Terrace 8,078 4 Wellington 1,146 I 02/09/77 07/26/74 & 04/09/76 Wellsville 1,494 SC 07/18/75 06/21/74 & 12/26/75 Wendover 1,001 07/25/75 08/15/75

aCodes are defined in Table 11. Two-letter designations after code are FEMA recommended actions in December 1979 SC - Special conversion to regular program (contingent on community enrollment) DS - Detailed study RM - Rescind map

49 -, Table 10. Continued.

Flood Insurance Program Participation (5/31/79)

Community Population Date of Hazard Policies Amount of Name (1975 Est.) Codea Entry Identified in Force Insurance

Cities & Towns (Cont.)

Wendover 1,001 1 07/25/75 08/15/75 West Bountiful 1,752 1 07/02/75 12/28/73 & 22 704,100 11/05/76 West Jilrdan 11 ,405 07/16/75 07/19/74 & 55 1,717,300 03105/76 West Point 1,379 4 Willard 1,117 1 DS 11/16/76 06/07/74 & 01/09/76 Woodruff 180 1 SC 12/ 16/75 08/22/75 $ 19,800 Woods Cross 3,219 lR 08/29/78 12/28/73 16,000 Yost 62 4

TOTALS 1,202,672 2,676 85,187,800

Source: 'Federal Insurance Administration, U.S. Bureau of Census.

aCodes are defined in Table 11. Two-letter designations after code are FEMA recommended actions in December 1979 SO - Special conversion to regular program (contingent on community enrollment) DS - Detailed study RM - Rescind map

Table 11. Number of Utah communities by code classification.

Communities Insurance Sanction Average Code Definition Status Population Number Population

lR Entered into regular program R N 15 146,950 9797 1 Entered into emergency program E N 147 967,273 6580 2 Suspended (from emergency program) a y 3 18,904 6301 3 Hazard area defined, 'community not in program n Y 37 23,294 630 4 Flood prone areas known to exist but not defined n N 29 38.314 1321 5 No known flood prone areas n N 20 7,937 397 Totals 251 1,202,672 4792

Insurance Status Coding (May 1979) R Eligible to buy both layers of insurance. E Only eligible to buy first layer of insurance. a No new policies or renewals but old policies are good until they expire with a one year maximum. n Not eligible to buy any insurance.

so e1 ible to buy insurance average a popula­ Fig,ure 9 provides the floodplain ordi­ tionof only 806, one can see where they nance for the town of Amalga as lilustrative might, feel that they would have difficulty of the typical wording used in Utah. Most handling the details of complying with the communities follow the wording s sted by federal ,program. FIA, except as to how they fi in the blanks, for convenience in adopt ion and In One difficulty a community may encounter order to avbid later hassle with federal is in drawing up an acceptable ordinance. officials because of an ordinance that falls The State of Illinois (1977) developed a short of federal standards. Nevertheless, model ordinance to help small communities in small communities experience continuing that state and'distributed it in a pamphlet difficulty in changing the FIA desired also containing supplemjintal information on wording in ways they feel necessary ~o fit its use and a reprinting of the National their local situation and then havIng to Flood Insurance Program rules and regulations negotiate its acceptance. From the perspec­ (Federal Insurance Administration 1976b). t ive of the federal program, separate unique

RESOLUTION II

RESOLUTION OF THE TOWN OF AMALGA PROVIDING FOR THE REVIEW PROCEDURE OF THE BUILDING PERMIT SYSTEM ADOPTED BY THE TOWN OF AMALGA

WHEREAS, the TOWN OF AMALGA has adopted and is enforcing ordinance # providing for the building code regula tions and Ordinance # providing for zoning regula tions, and

WHEREAS, Sections and of the aforesaid prohibits any person, firm or corporation froIT erecting, constructing, enlarging, lteril repaIrIng, improving, moving or demolishing any building or struc- ture without first obtaining a separate building permit for each building or structure from the Town Clerk, and

WHEREAS, the TOWN BOARD must examine all plans and specifications for the proposed construction when application is made to him for a building permit.

NOW THEREFORE, BE IT RESOLVED by the TOWN BOARD OF AMALGA, UTAH as follows:

(1) That the TOWN BOARD shall review all building permit applications for new construction or sub­ stantial improvements to determine whether proposed building sites will be reasonably safe from flooding. If a' ~roposed building site is in a location that has a flood hazard, any proposed new construction or substantial improvement (including prefabricated and mobile homes) must (a) be designed (or modified) and anchored to prevent flotation, collapse, or lateral movement of the structure, (b) use construction materials and utility equipment that are resistant to flood damage and (c) use construction methods and practices that will minimize flood damage, and

(2) That the TOWN BOARD shall review subdivision proposals and other proposed new developments to assure that (a) all such proposals are consistent with the need to minimize flood damage, (b) all public utilities and facilities, such as sewer, gas, electrical, and water systems are located, elevated and con­ structed to minimize or eliminate flood damage and (c) adequate drainage is provided so as to reduce exposure to flood hazards; and

(3) That the TOWN BOARD shall require new or replacement water supply systems and/or sanitary sewage systems to be designed to minimize or eliminate infiltration of flood waters into the systems and discharges from the systems into flood waters and require on-site waste disposal systems to be located so as to avoid impairment of them or contamination from them during flooding.

PASSED and ADOPTED by the TOWN BOARD OF AMALGA , at a special meeting thereof, held on the 2nd day of January , 1975.

Mayor Dale Rindlisbacher lsi

ATTEST:

Marilyn H. Hansen lsi Clerk

Figure 9. Typical- floodplain management ordinance.

51 ordinances for each community poses major prevent development in all areas subject to difficulties because of the time required to inundation by 100-year floods on alluvial review them for compliance with the national fans; the areas are too large and the bene.,. s tanrlards. fits too few. A more promising alternat.ive is to distribute flood proofing information so that those building in these areas can do Floodplain Occupancy Choices a better job of protecting themselves against shallow flooding entering buildings or Despite the large number of cloudburst basements. In many cases, deflecting and spr ing snowmelt floods which have been levees set back from a building can divert recorded in Utah, the damage caused to waters during short cloudburst flood per~ods pr ivate property has been remarkably small. into drainag.e ways where damage will be As of 1979, the Utah Division of Water mini~ized. _ . Resources estimated Utah' s annual flood damage to average about $4 mi Ilion of a An additional problem frequently en­ national total that would now be about $4 countered on alluvial fans in irriga.ted billion (McCrory et al. 1976). Since Utah areas is that canals cross the fans parallel has about 0.5 percent of the United States to the contours and intercept flood waters population, damage rates per capita (and by coming downhill. The canals then fill, implication per unit value of structure) overtop away from the stream, and cause are about 20 percent of those nationwide. flooding in areas where no problem would Furthermore, the damage records for h istor i­ otherw ise occur. Th is problem could be cal Utah floods cited above indicate that greatly alleviated by canal design for flood damage to pr ivately owned structure has been bypass or to discharge excess waters at a very small fraction of the total. controlled discharge points, but a regulatory effort will be needed to make this occur. This fact implies that Utahns have The danger of canal flooding greatly in­ used sufficiently good judgment in their creases as an area converts from agriculture floodplain oC.cupancy decisions to avoid t.O urban, and the canal companies are slow to frequent flood damage. Urban development in provide for this contingency as urbanization Utah is generally on larger lots where the occurs. Each situation, of course, should be shallow flooding can pass between bUildings, individually analyzed to determine what and buildings in flood prone areas have measures are appropriate. generally been built high enough off the ground to be safe. In the field surveys of An additional problem encountered in the Utah's flood prone communities reported in field interviews performed in as part of this the next cbapter, a few scattered homeowner.s study was that some individuals living in (Willard) and businesses. (Moab) were found to communities enrolled in the flood insurance have short walls to deflect flood waters and program were being told by their insurance mud flows. agents that they could not buy insurance. The matter could be quickly resolve.d when the The quest ion that needs to be asked to query was properly directed, but this did determine the need for floodplain management not occur in many cases. Better information is (in terms of Figure 1) whether the land needs to be made available to eligible use decisions being made by private indi­ floodplain occupants on the mechanics of viduals based on their perspective of the purchasing the insurance. One wonders how physical, economic, social, culturaL, and much .of the reason that so few policies are governmental factors are reasonable from a sold is the fault of poor information on the higher level perspective in the governmental part. of property owners and how much is the d imens ion? The two cons iderat ions most fault, of poor information on the part of likely to make them unreasonable are that 1) insurance agents. floodplain occupants may be unaware of the devastation that an event as large as the With respect to reasons seen from a 100-year flood can bring or 2) higher level high.er level per.spective for reducing perspectives may see reasons for reducing floodplain land use intensity, the greatest floodplain land use intensity not seen by the need on alluvial fans is to protect recharge occupants. areas for groundwater development. Most groundwater recharge in desert climates With respect to the risk of devastation occurs on fans. Most of the water recharged from rare events, the shallow,..flooding on from the ephemeral streams emerging from alluvial fan and valley areas is very un­ mountain canyons is flood water. Care likely to threaten human life or destroy needs to be exercised to make sure that the buildings (except at the apex immediately flood water control system does not un­ below where sediment laden waters discharge necessarily restrict recharge and that flood from mountain canyons). It would not appear waters do not become polluted and contaminate wise from the viewpoint of. economics to under'ground aquifers.

52 --"

CHAPTER V SURVEY OF FLOOD PROBLEMS

Survey Approach communities into the categories of 1) not mentioned and therefore presumably not having Floods cause economic loss, social a major flood problem (Code 5, Table 10), 2) disruption, and environmental damage. As suspected as having a hazard but with the described in Chapter II, these primary locations and degree of hazard not identified flooding impacts induce people and inst itu­ (Code 4), and 3) having a mapped floodplain tions to respond in ways that generate waves area but choosing not to join (Code 3). of economic, social, and environmental Member communities were divided between those effects. A survey of flood problems thus 1) having joined the emergency program and 2) needs to ident ify both pr imary problems having joined and also having a detailed caused by the flooding but not being respon­ study underway. The classifications used ded to appropriately and the secondary in the sampling were based on community problems associated with undesirable impacts status as of November 1977; the status of structural and nonstructural programs to of many communities has changed since then to deal with flooding. that updated on Table 10. This survey considered all 251 Utah Communities were classified by size as communities, whether or not they have a known an index of both the nature and magnitude of primary flood problem, because of the un­ the flood problem and of ability to cope with certaint ies in determining whether a hazard it. Nature relates because larger com­ exists in marginal cases and because national munities attract more people unaware of local nonstructural programs may have secondary cond it ions and hence more prone to make effects in communities with no primary unwise use of floodplain lands. Magnitude problem. For example, a community exposed to relates because more people bring greater very minor flooding may be forced to under­ population densities and often faster growth take greater nonstructural effort than is rates, both factors making flood hazard warranted by its situat ion, and the ef fort ident if icat ion and floodplain management may generate undesirable economic, social, more d iff icu It. Ab il ity to cope relates or environmental impacts. One purpose of the because larger communities have a greater tax survey was to determine whether such con­ base for financing community programs and sequences were actually occurring. usually greater technical expertise on staff. Classification by FEMA program status pro­ Available study resources, however, did vides an index of the support of local not permit examination of all 251 com­ officials for the national program for their munit ies. The approach was to examine a community. sample to identify problems for more detailed analysis in a second round reported in the This two-way classification divided the next chapter. Th is chapter present s the counties, cities, and towns of Utah into the sampling procedures, describes what was found 30 groups shown on Table 12. No communities in each community examined, and describes the fell into the seven classifications marked problems found to deserve further analysis. "none." One out of every e igh t in each remaining 23 groups was selected by using a Sampling Piocedure table of random numbers. A minimum of one community was chosen from each group to make Since the project budget would only sure that each was represented. The 26 permit visiting about 30 of the 251 counties, cities and towns and 6 counties chosen by Cities, and towns listed in Table 10, a this process are listed on Table 12. The sampling ratio of about one out of eight was location of each is shown on a map of Utah selected. Stratified samples were used for in Figure 10. both counties and cities or towns. Counties were classified between the densely populated Information Sought by Community areas along the Wasatch Front and the more sparsely populated rural areas. Cities The process for gathering information on or towns were classified according to the the 32 selected communities combined 1) population groups of under 1,000, 1,000 to collection of information that could be 5,000, 5,000 to 50,000, and over 50,000. A obtained about the problem from maps and second sort of c lass if icat ion was accord ing other available sources in preparation for a to the status of community involvement with site visit, 2) a field visit to observe the Nat ional Flood Insurance Program. The selected flood problem areas on the ground, classifications used divided nonmember and 3) interviews with engineers, planners,

53 Table 12. Study sample communities.

Flood Insurance Program Status (10/15/77) Non Members Program Members Suspected Hazard Detailed Not Not Mapped Study Code (Table 11) Mentioned Mapped Floodplain Emergency Underway 5 4 3 1 and 2 lR

A. Counties Location Wasatch Front None Cache None Box Elder None 2 l Other None Piute Uintah Washington Emery B. Incorporated Cities and Towns Population 3 » 50,000 None None None Ogden Provo 5 5,OOD-50, 000 Spanish Fork4 Washington None Sandy Bountiful Terrace Pleasant Grove 6 1, 00D-5, 000 Garland West Point Beaver Hurricane Helper Hyde Park Parowan Richmond < 1,000 Garden Wales Millville Corinne Castle CitY7 Kingston E. Layton Dale8 Bluff Koosharem Kamas Midway

1Entered emergency program 11/30/77. 2Hazard identified 11/8/77, entered emergency program. 3Entered regular program 2/2/79 • . 4Hazard area designation withdrawn by FIA, exempt from program. 5Entered regular program 9/29/78. 6Suspended, pending approval of revised floodplain management ordinances. 7Unincorporated town, membership as part of San Juan County. 8Detailstudy in review and appeals period.

·and local political leaders. Since some discussing the community with FIA officials communit ies had many scattered flood prone to~obtain insights on the community's re­ areas,·· a limited number had to be preselected sponse to the federal program, and 5) obtain­ for investigation. The preselection was ing descr ipt ive informat ion on the local based on 1) coverage of the diversity of economy in order to have a general idea as to floodplain types found within the community the pressures for development in the hazard in terms of stream size, extent of floodplain area. development, and pressu·re for new develop­ ment, 2) ease of access and proximity to one The field visit combined observations of another, and 3) existence of a hazard to field conditions, taking snapshots of items private property. Floodplain management for of interest, and conversations with local public lands was not considered within the residents. The observation schedule included primary focus of this study. 1) noting floodplain land use as residential, other urban, cropland, or natural, 2) classi­ The preparation before the site visit fying any buildings observed on the flood­ included 1) obtaining available topograph ic plain by characteristics related to their and flood hazard maps (flood hazard mapping susceptibility to flood damage, 3) noting the status by community is shown on Table 10), 2) extent of new urban construct ion, 4) not ing inspecting maps of the upstream watershed any observable flood proofing, 5) noting any area and the floodplain in order to under­ flood marks or signs of past damage, 6) stand better the source of the problem­ noting any man-made constrictions that may be causing flows and geomorphological conditions contributing to the flood problem, 7) noting on the floodplain, 3) consulting Utah's flash any evidence of past efforts to increase flood history or stream gaging records to see channel conveyance, and 8) noting any obvious if any floods have occurred recently, 4) discrepancies between the floodplain mapping

54 a n'd 0 b s e r v e·d g r 0 u n d con d i t ion s • L 0 cal and 4) individuals who any of the first residents encountered were asked if they three suggested as having suffered severe recalled any flood exper iences or local flood damage or haVing strongly objected efforts to control flooding and whether they to floodplain regulations. The interview were aware of and, if so, how they felt about with the engineer was to pursue such topics the FIA program. as 1) descriptive information on historical floods, 2) ,descr ipt ive informat ion on any In scheduling interviews with local local structural or channel maintenance officials, the goal was to include 1) an efforts, and 3) recommendations on indi­ engineer familiar with the local situation, viduals to include in the fourth group to 2) a lawyer or planner familiar with local interview~ The interview with the lawyer/ bu ilding code and zoning problems, 3) a planner was to explore such topics as 1) poli tical leader f ami liar with the local description of community floodplain manage­ deliberations on the FIA program and with ment efforts, 2) identification of any community prospects and feelings on growth, privately proposed development that had been

UTAH

o 10 20 30 40 &0 I , , , I , SCALE OF MILES • ORIGINAL SAMPLE o ADDED IN CHAPTER VII

TOOELE

JUAB

MILLARD

GRAND °MOAB

BEAVER WAYNE

PAROWAN IRON • GARFIELD

BLUFF KANE •

Figure 10. Location map for sample communities.

55 proh ibited because of its floodplain loca­ agr:icultural land and the worst during. this l ion, 3) identification of any privately 31':y~,ar period only damaged two or three constructed development that was flood buildings. proofed or otherwise modified in design because of the hazard, 4) description Box Elder Creek, which originates ~~ar of floodplain management program enforcement the reservoir at Mantua, flows onto an procedures and an estimate of their cost, 5) alluvial fan at the base of the mountains; explanation of any nonconforming floodplain and passes about a mile downstream through development that may have been observed Brigham City, poses the greatest flood damage during the site visit, and 6) assessment of potent ial in the county. South of Br igham the FIA program from their viewpoint and as City, Perry Creek, Willard Creek, and Three r ece ived by the people of the community. Mil,.e Creek threaten the towns of Perry and Local polit icians were to be asked about 1) Willard. These and other creeks flowing out remembered historical floods, 2) attitudes in of smaller mountain canyons pose danger for the community toward the national flood the unincorporated areas between Perry and insurance program, 3) memories of discussion Willard and south of Willard to the county on whether or not to join the program, 4) line. Gravel pits in this area may be causing expectat ions for economic change in the a ~ignificant increase in flood risk in that community, and 5) assessment of whether the they may capture flood flows from the chan­ program is helping or hurting the community. nels, impound water, and later break loose Ques t ioning on many of the above po int s did discharging stored water and gravel onto the not produce useful information in many of the property below. communities, and such replies are not de­ tailed below. Box Elder Creek has flooded Br igham Ci ty per iod i cally since the city' s set t lement in Findings for Counties the mid 1800s. The most serious flood occurred in February 1911 when snowmelt, Box Elder County possibly augmented by heavy rain, produced extremely high runoff. The clogging of Box Elder County contains vast sparsely br~dge openings by debris diverted water into inhabited desert areas and a number of the city, bridges were washed away, and a growing communities at the north end of the section of railroad track was washed out. Wasatch Front urban area in the eastern part Emergency ef forts were required to protect of the county. Flood hazard areas have been the powerhouse in Box Elder Canyon. While ident if ied, and the county has entered the some flooding of basements was recorded on emergency flood insurance program permitting June 3,1963, there has been no recent its 5138 residents who live outside of serious flooding. Nevertheless, in realiza­ incorporated towns and cities to purchase tion that a 100-year flood would cause insurance. As of May 1979, however, only one extensive damage in the city, the county policy was in force (Table 10). Department of Emergency SerVices conducted a flash flood exercise in 1978 in Br igham City Although the Bear and Malad Rivers flow in which 300-400 people were evacuated. through the county to where they join up­ stream of flowing irito the Great Salt Lake, The City of Willard has experienced flooding damages along the rivers have been periodic flooding. Willard Creek basin small and largely agricultural. Both rivers had a flood in 1923 and another in 1936 which are deeply incised in narrow canyons until washed mud and debris into town and caused they open into swampy areas near the lake, two' deaths in the first case and substant ial and streamside locations thus do not attract pro~~rty damage in both cases (Woolley 1946). much development. A~cording to county Fol,lowing the 1936 flood, the Civilian officials, there are three potential flood Gonservat ion Corps '(CGC) did a substant ial damage locations along the Bear River and amount of terracing upstream from the town. none along the Malad River. As also shown on The Bureau of Reclamation or the CGC also the flood hazard maps ~or the county, the bu'llt a levy between the creek and the City three locations where tesidential property of, Willard shortly afterwards, and flooding could be flooded are: 1) downriver a shott ftotl! Willard Creek has not caused flood distance from Corinne; 2) near Hampton's dainage since. The area behind the levy is now Crossing between Fielding and Collinston filled with rocks and sediment. Inspection (Pony Express Station on historical lists); and evaluation of these old deSigns could and 3) downriver a short distance from provide valuable clues in developing more Bear River City. effective future measures for controlling floods and mud flows emergirig from mountain Butler and Marsell (1972) describe 17 ca~yons onto alluvial fans. cloudburst floods as occurring in the county between 1939 and 1969 with 12 of these . Recent floods occurr~d in Willard on occurring in the incorporated ateas of August 13, 1978, and July 23, 1979. In the Brigham City (6), Willard (4), and Snowville f i:rst case, a cloudburst on Willard Peak (2). The other five occurred at Fielding, caused water to flow down the face of the Howell, Perry, Plymouth, and Promontory. A wountain between two canyons. Mud. rocks. flash flood thus has been occurring somewhete and debris filled the Pine View perimeter in the county about one year out of two, canal for one mile, causing the irrigat ion but most have caused only isolated damage to water. to overflow the banks and add to the

56 flooding. Basements of three homes were River east of Portage, 2) Bear River south of filled with mud and debris, causing an Fielding, and 3) a low area between the estimated $65,000 in damages. There were interstate highway and railroad south of also ext ens ive damages to lawns, orchards, Honeyville. and gardens to bring the total, including . some wind damage, to about $250,000. The first or Malad River location was found to contain low lying pasture and None of the three homes were insured wasteland with no structures that would be under the FIA program even though they were damaged by overbank flooding and no apparent eligible. Two of the homeowners received pressures for future development. Much of the flood damage assistance under a USDA program area at the second or Bear River location was which covers farms over 5 acres in size. The also pasture and wasteland, but there were o~her homeowner had less than 5 acres and also significant acreages of hay. Also a received no financial help. All three historical site (Pony Express Station, now a said that they were unaware of federal farm house and outbuildings) at Hampton's insurance even though its availability had Crossing, with an estimated value of over been announced in the newspapers. $100,000, is subject to flood damage. An old steel highway bridge at Hampton's Crossing On July 23, 1979, debris and mud washed would probably obstruct large flows. Location down the mountain, damaged one home, and 3 was found to contain pasture and wetlands crossed the state highway. The damaged with no structures of any kind; however, homeowner was outside the mapped 100-year several miles to the south, the Brigham hazard area and reported that he had tried City Airport is shown within the flood hazard but been unable to purchase flood insurance. area on the FIA map. In the western part of the county, there In summary, Box Elder County is trans­ has been occasional flooding in the Grouse versed by two rivers with defined flood­ Creek area, but very little development is plains. No significant damages have occurred affected. There are only about 30 homes in to buildings in these areas historically; the entire area. The main damage is from the only building found in the examined washed out roads. port ion of the 100-year floodplain has been standing for over 100 years essentially The cit ies and unincorporated areas in undamaged. Cloudbursts causing flows out of the eastern part of the county have the mountain canyons· or down the steep mountain­ greatest development pressures as well as the sides occur, however, every few years and greatest flood hazards. Subdivisions and account for the bulk of the flood damages individual homes are being built at several currently inflicted on the county, and these locations along the base of the mountains problem areas are not well defined on the from Beaver Dam on the north to the county flood hazard maps. While residents of the line at the south. The area south of Willard unincorporated portion of the county are is the fastest growing. The developments eligible for flood insurance, the occupants close to the base of the mountains are of exposed areas at the base of the mountains generally exposed to hillside flooding of the are generally not aware of that fact and at sort descr~bed for Willard. This danger, least some have been told that they cannot however, should not necessarily preclude obtain it. Even though Box Elder County is a hillside development. Building sites program member, its cit izens are t ak ing at the base of the mountains are particularly 1 ittle advantage of the program, and f lood­ attractive because of the view they offer of plain management efforts are minimal and the valley below, and these bench areas are doing little to reduce future flood risk. usually much less product ive agr iculturally Specifically, the program does not seem to be than are valley soils. Land use planning focusing sufficiently on the hazard at the needs to weigh the tradeoffs, and the build­ base of the mountains, and the regulatory ing construction practices used on these program is not extensive enough to cause bench areas need to protect the structures. secondary problems. Box Elder County is participating in the Cache County FIA program. It adopted the uniform building code in 1973 and became eligible for flood Cache County is the second of the two inaurance in 1974. Out of 17 towns in the urbanizing Wasatch Front counties in the county, 13 are now eligible for insurance, sample (Table 12). Flooding is known to but this group does not include Snowville and occur in the county, but the hazard areas Howell where flash flooding has occurred. have not been mapped, and the county has not As of May 31, 1979, 33 policies had been applied for membership in the National Flood issued in Brigham City and 1 elsewhere in the Insurance Program. The 2699 residents of the county. The detailed study is in for the un incorporated areas of the county are thus county was completed late in 1979. not eligible for the insurance. Three flood hazard areas were selected The county covers the Utah or south half for field observation. Each is shown to have of Cache Valley with farming land on the extensive flood hazard areas on the FIA flood valley floor and over 90 percent of the hazard boundary maps, dated February 28, population living in cities and towns along 1978. The three locations were: 1) Malad the valley margins. The urban expansion is

57 centered around Logan and occurring in Insurance Program does not seem to be based the Incorporated areas with significant on any opposition to mapped areas or regul~­ amounts also occurring in unincorporated tory~ requirements and the cost to the county areas. As in Box Elder County, development of enforcing them. In A\lgust 1978, th~ has been attracted more to bench areas around county passed a "sensitive area ordinance". the perimeter of the valley than in the that requires, throl,lgh the building permit relatively swampy lowlands subject to river~ process, new buildings in the floodplain to ine flooding on the floor of the valley. be .designed with foundations sufficient to Some recent shift, however, seems to be withstand 100-year flood flows, have no resulting from the greater escalation of land basements, and have the first floor above the prices on the bench. 100-year flood elevation. All persons wishing to build in the floodplain must, in Butler and Marsell (1972) d~scribe 13 addition to meeting the aforementioned cloudburst floods oc~urring in the COunty requiremen,ts, file a statement with the between 1939 and 1969. Six occurred near county acknowledging the flood hazard and Logan, tWO each near Clarkston and Smith~ assOming all liability for flood damage.' 'A field, and one each near Hyrum, Mendon, and county map has been p'repared from SCt) data Providence. The events large enough to cause showing areas along rivers where flooding significant damage were a gravel and mud flow has occurred. The county has no flood out of Blacksmith Fork into Hyrum May 30, control projects, but annually cleans river 1939, a wall of water emerging out of Cold channels above and below road crossings. Water Canyon at Mendon September 12, 1939, a cloudburst filling some Clarkston basements The failure of Cache County to apply for with water August 22, 1958, a cloudburs!: in program membership relates more to county the mountains above Providence on August 18, staff giving higher priority to other matters 1959, that flooded a dozen homes in that town and never gett ing around to, complete neces­ and littered the bench areas in Millville s ary paper work. Th e exper ience s ugges ts a with boulders and mud, a cloudburst on need for FIA to minimize the paper work August 25, 1961, that inundated 1500 acres reqUirements which can be interpreted as and caused $20,000 in damages at Clarkston, req~esting information of a sort on which the and the flooding of Smithfield basements by community has limited technical expertise. Summit Creek June 7, 1964. Significant flood damage to res idences also occurred in Logan 'In conclusion, the unincorporated areas due to local runoff from heavy rains on of Cache County have experienced very little August 22, 1977, on the bench at the mouth flood damage, and the county has an ordinance of Dry Creek Canyon. toredvce exposure to damage from future building in the floodplain. One caution that Riverine flooding occurred along the the county should consider is that while Logan River in 1896, 1897, 1907, 1912, 1916, frequency analyses of the gaged records 1921,1971, and 1972; however, information on indicate that the IOO-year flows on the Logan areas flooded and flood damage is nonexistent River and Blacksmith Fork are on the order of fo·rmost of these floods. The most SeVere 2000 'cfs, Figure 8 indicates that flows of flood on the Logan River occurred in May 1907 around 4500 cfs have occurred from other with a discharge of 2,480 ds. According to drainage basins of similar size in the Great Table 3, this exceeded the IOO-year event. Bas in port ion of Utah. Even though such The largest flow in recent years was 1,680 events may be much rarer than the 100-year, cfs in June 1971 (Corps of Engineers 1973). it would behoove the county to act to make Housing along the Logan River in the City of flood insIJrance available to its residents Logan is the prime risk area subject to befo~e such floods occur. The county appears riverine flooding in the county. Logan and to already have a floodplain management several other cities in the county are program that would come close to qualifying, participating in the federal flood insurance actuarial rates would generally be low, and program. the benef its of having such coverage when a major flood comes would be large. The Blacksmith Fork River and Spring Creek also have exper ienced numerous floods Emery County since the turn of the century. The last significant one occurr ing on the Blacksmith Emery County is in a rural part of the Fork was in May 1971. At that time, snowmelt s tai:~ with low populat ion dens ity but in an produced a peak flow of 825 cfs (Corps of area where energy resource development could Engineers 1975). Other s,mall rivers and lead to substantial population growth in the creeks, such as Cub River and High Creek, near future. The county has entered the occasionally flood adjacent pasture and regular flood insurance program, but only one farmlands. There has been no Significant small policy is in force. riverine flooding in the county since 1972. As was the case for Box Elder County, the Butler and Marsell (1972) describe 48 damages that have occurred have been caused cloudburst flOOds occurririg in the county by flows from the smaller canyons such as the between 1939 and 1969 with 44 occurring since Dry Creek case cited above. 1957. Most of the floods were in isolated areAs where the principal damage was the The reason the county has not made closure of roads and small losses to agr i­ application to join the National Flood cul'tural property. Damages to scattered

58 homes f~om runof f from localized intense cost of $11,000. Other work has been done showers were occasionally reported. just north of town to protect properties , • • ,"t along the west bank of the Green River. The principal hazard areas in Emery Costs of these structures were unavailable. County are located along the numerous washes south of Castle Dale, near Cleveland, Emery County entered the FIA program in west of Green River, and near Ferron. The July 1975. However, floodplain maps were not 100-year flood hazard is mapped along Ferron published until January 1978, and ,only one Creek, Cottonwood Creek running from the policy is now in force. Intervlews wIth northwest to southwest near Castle Dale, and officials in Green River indicated that Huntington Creek near the City of Huntington. the insurance program is little known and Some areas along the San Rafael and Green probably misunderstood. The officials sug­ Rivers in the county are also within the gested that the res idents of Green River and 100-year floodplain. the surrounding area have lived with the flood potential of the Green River for many Flood ing in the county has been ma inly years and generally assessed the potent ial caused by severe summer thunderstorm activity damage to insurable assets to be low. Those and the resulting runoff and debris washed who assessed the probability of damage to be down various washes and Cottonwood and relatively high had invested in flood Huntington Creeks. A boy was drowned by a proofing or measures such as those described flash flood near Orangeville on August 4, above. Little proofing activity was evident, 1900. Severe thunderstorms in August and however. The unincorporated areaS of the September of 1941 caused damage to hig~ways county are currently almost entirely zoned and br idgework at Emery and Green RIver. for agr iculture, and the farmsteads are The heavy rains of July and August of 1957 generally on high ground. Hence, the flood caused floods near Castle Dale, Orangeville, insurance program has virtually no impact. A Green River, and Ferron. Approximately recent ordinance which requires that a $10,000 in damage was inflicted to several water hookup be secured before the county homes in Orangeville. Damage to crops and to will issue a building permit may also reduce roads in the above communities was also expe­ future flood problems. r ienced. Flooding again swelled Cottonwood Creek in 1964 destroying newly installed The Ferron watershed project has been approaches to the new bridge near Old Mill completed by the Soil Conservation Service Dam near Orangeville. In 1965, Huntington under the P.L. 566 program. This project Creek flooded causing damage to Huntington consists of a reservoir (Mill Site Dam) above City Water Works estimated at between $8,000 Ferron and canals and debris basins at lower and $12,000. elevat ions. Ferron Creek and several washes drain into the reservoir. Average annual Heavy rainstorms in 1967, 1968, and in flood protection benefits were estimated in 1969 caused flooding at Orangeville, Green the work plan to be $27,700 (U.S. SOil River, Ferron, Cleveland, and Emery. Most of Conservation Service 1965) to farming areas the damage from the flooding in this 3-year south and east of Ferron. The project work period was to roads, bridges, and canal plan indicates that a flood in 1947 cost, two structures. Several canal and irrigation lives and washed out ditches and canals-­ structures were washed out or filled with as well as causing heavy damage io roads. boulders and debris near Ferron. The drug­ The USGS streamgage was apparently rende~ed s tore basement in Ferron was filled with inoperable by this flood, and no peak d lS­ water and debris causing damage to inven­ charge was recorded. An est imated ,peak tories and the furnace. Crops in the discharge of 4,180 cfs was recorded durIng a Ferron area were also damaged extensively. 1952 flood (Table 3). Equation 2 suggests the The most damaging historical flooding possibility of a flood as large as 15,400 cf~ appears to have been centered near'Ferr?n ~nd at this location. Orangeville although some road and bUlldlng damage has been experienced at Green River. Emery County thus seems to be a, case where the county government has pushed Observat ion of the hazard areas on the through the necessary applications to enroll site visit indicated no buildings within the in the program even though little insurable hazard areas- near Castle Dale, Cleveland, property is found in its unincorporated Huntington, or other small communities in the areas. Participation seems to provlde several county. Floodplains are used for cropping or benefits for the county. It permits the grazing, and these activities have suffered purchase of low cost flood insurance against most of the damages from the flooding that damages caused by the severe thunderstor~s has occurred. A brief interview with a characteristic of the area. The floodplaln county zoning offi~ial suggested that future management regulations provide an additional development will not be permitted in the tool that can be used to implement the county unincorporated areas of Emery County and that planning goal of keeping any urban develop­ the 1333 current residents of those areas all ment associated with energy resource develop­ live on farms. Urban development does exist ment within the incorporated towns. in the floodplain at Green River. A motel operator, east of the town has invested in Piute County bank stabilization on the east bank -of the Green River at a cost of $9,000 in 1972 and Piute County is very sparsely populated some terracing and rock levying in 1974 at a with little potential for immediate growth.

59 Flood hazard areas were mapped in November Pe?k. recorded discharge on the East Fork of 1977, arid the county joined the federal flood the Sevier River near Kingston is 2030 cfs on insurance program the following March. May> 12, 1941, and a frequency analysis of the Unincorporated areas of the county have only recorded annual flow ser les ind icates. : a 190 residents, the fewest of any county in lOO-year flood of 1839 cfs (Table 3). the state. Butler and Marsell (1972) note 11 Equation 1 suggests a maximum flow of 6600 cloudburst floods in the county from 1939 cfs for a drainage area of this size, and through 1969, 8 in Marysvale, 2 in Kingston, the FIA study estimates a i lOO-year flow of and 1 in Circleville. The only damages they 28,000 cfs. This thus seems to be a ca$e noted from any of these floods were from road where flood ing much worse than any ever closures in canyon areas. recorded could well occur, put the FIA flow seems unreasonably high. As examples, heavy rainstorm floods have been recorded in Marysvale and in Kingston Br ief interviews witb farmers in the Canyons. In July 1955, a flash flood in the area indicated that they assess the proba­ mountains northwest of Marysvale caused some bility of flash flooding to be quite high but $19,000 damage to the roadbed of U.S. Highway losses to crop and livestock enterprise$ to 89 and rendered some 80 acres of baled hay be relatively low. The small amounts of useless for feed. Keetch (1971) notes damage which occur rather frequently destroy, damage to homes in Marysvale in August 1958 at ,most, a corn silage crop, or about half of from flash flooding on Cottonwood Creek, the second alfalfa harvest for the season Bullion Canyon, Revenue Canyon, and Beaver Such losses are not cons idered enough to Creek. Additional flash flooding occurred in justify changing farming practices. Farmers July 1965 and again in August and September operate as if no flood hazard exists and of 1967. Again, U.S. Highway 89 north of replant in the same pattern after losses Marysvale was broken up by the onrush of occur. These attitudes provide empirical water and boulders from the mountains, and support for the business activity strategy in some alfalfa fields east of Kingston were the face of flood hazard that has been inundated by flooding of the East Fork of the outlined as theoretically optimal by Brown Sevier River. Flash floods in July 1968 (1972) and Brown et al. (1972). again covered the highway with debris and mud, but greater damage was caused by hail Even though Plute County is now in the which. destroyed several acres of corn. emergency program, no specific ordinances Approximately $30,000 in crop damages have been passed to indicate interest in occurred near Marysvale during a July 1975 future participation in the program. Some flash flood. In earlier storms, Highway 89 communities within the cQunty have been was blocked by a washout on July 11, 1936, a mapped but not the unincc;>rporated areas. railroad br idge was damaged on July 24, 1925, With almost no flood damage reported to and half of the county's hay crop was de­ buildings in the over 100 years since settle­ stroyed by Sevier RiVer flooding in early ment and little prospect of new construction August 1916 (Woolley 1946). In over 100 in hazard areas, Piute County has no struc­ years of record, however, the only noted tures with a flood problem other than that damage to buildings in either the Marysvale assdciated with events more rare than any or Kingston areas was the relatively small wh ich have occurred. Larger los ses occur to amount inflicted in Marysvale in August 1958. crops and roads, but these do not appear Noh is tory of damage to buildings could be large enough to justify major adjustment in found. for the unincorpo~ated portions of the farming practices or road alignments. In county. short, a more comprehensive floodplain manijgement program would not seem to be Piute County and Kingston and Marysvale juseified. officials suggested that the FIA program does not suit the needs of the county since most Uintah County damages occur to uninsurable crops, roads, and bridges. Marysvale officials further Like Emery County, Uintah County is in a claim that the mapped flood hazard area, rural part of the state currently with particularly along the river around where the low population density but likely soon to Denver and Rio Grande Railroad right-of-way experience substantial growth wtth develop­ passes through town, is not correct. They ment of its energy resources. The county was instead visualize a flash flood problem s e lec ted f rom the s amp Ie of nonmember wherein heavy rainstorms wash boulders and communities having an identified hazard area, debris onto Highway 89 and onto cropland on but:; U intah County entered the emergency both sides of the highway. The east fork of program in November 1977, one month after the the Sevier River also floods over its banks sample was drawn. The population of 12,145 at a series of bends where impediments to living in unincorporated areas make Uintah free flow divert the water onto .alfalfa County the third highest in·the state in this fields. The flood problem thus comes from rega~d. both flows out of the mountain canyons and overflow of the rivers in the valleys. Road damage was caused by flash flooding in August 1912, September 1927, and September The drainage area of the East Fork of 1938. (Woolley 1946). Butler and Marsell the Sevier RiVer near Kingston is 1250 square (1972) describe 20 cloudburst floods in the miles (Utah Water Research Laboratory 1968). county, 7 in Vernal, 2 in Maeser, and 11 in

60 unincorporated areas. Only 2 of the 11 constructed in the Maeser area and used to caused reported damage to buildings. A flood justify reduction of the size of the mapped on August 25, 1955, brought water 2 feet deep floodplain were sufficient to hand Ie the around a house in Dry Fork Canyon and washed flash floods of 1968, 1972, and 1974. boulders and silt onto the yard. Recorded channeling and canal structure costs totaled approximately $28,000, but . On September 1, 1909, a man was drowned other costs incurred in developing the while trying to drive a wagon across Ashley canals were unavailable. Creek. . On July 4, 1925, an 8-year old boy was drowned when he was swept from an auto­ Uintah County is apparently experiencing mobile (with nine occupants) which rolled significant pressure for urban development on down a wash during a flash flood. A year its floodplains. The primary problems are earlier, two boys narrowly escaped death when a long desert washes where flood i ng pat terns surprised by a 10-foot deep flash flood are more consistent from storm to storm than (Woolley 1946). On July 19, 1965, flood­ they are on alluvial fans. Flooding, how­ waters filled the basement of a home at ever, is shallow, and the appropriate non­ Ashley. structural program and regulatory measures to enforce it are not well defined. Th is study uncovered records of floods near Maeser, La Point, Jensen, and Randlett Washington County in 1955, 1956, 1961, 1963, and in 1965. Flooding in areas contiguous to Ashley Creek Washington County is in an agricultural north of Maeser occurred as did flooding from and growing resort area in the extreme the Uintah River near Randlett and flash southwestern corner of the state. The county flooding causing boulders and debris to wash entered the emergency flood insurance program from the foothill regions near La Point and in October 1975, the hazard area mapping was Jensen. The Green River occas ionally released in February 1978, and 7 policies for floods over its banks at a series of bends $278,000 were sold by May 1979. This is near Ouray, but dwellings are located on high the most insurance for any county in the ground above and to the north of the river. state outs ide the two most populous Wasatch Several roads in the area, including portions Front counties. The population of the of state highway 88, are in the 100-year unincorporated area of the county is 2087. flood zone and frequently under water. A flood on October 7, 1916, was recorded Woolley (1946) lists over 15 cloudburst as destroying bridges and buildings in Vernal floods for Washington County beginning in (Woolley 1946). Ashley Creek flooded due to 1863. Butler and Marsell (1972) list 36 a heavy rainstorm in September 1955 causing cloudburst floods for the county. Of these an estimated $3,500 damage to a $15,000-home 36, 12 were listed for st. George, 12 for in Maeser. Some $900 damage to a dwelling smaller incorporated towns, and 12 for near La Point was caused by flooding during unincorporated areas including 5 in Zion the same storm. In June 1965, the heaviest National Park. An August 25, 1944, flood rainstorm experienced in several years damaged park buildings. On September 17, caused Ashley Creek to flood the basements of 1961, 5 members of a hiking party of 26 were 11 homes. Repair costs were estimated at drowned by a flash flood on the Virgin River approximately $ 700-$1 ,000 per home. Addi­ in the park which crested at a 14-foot depth t ional damages were caused to hay crops in in some narrow gorges. No other damage to Jensen and Maeser and to roads and bridges buildings in the unincorporated area of the near Randlett as a result of the same floods. county was noted by Butler and Marsell (1972), but flooding was frequently mentioned U intah County entered the emergency as causing considerable damage to roads and insurance program in November 1977 after highways and disrupting traffic. According successfully negotiating changes in the to the earlier records compiled by Woolley boundaries of the flood hazard zone near (1946) buildings were damaged by flooding in Randlett and north of Maeser. The county's 1863, 1870, 1872, 1896, and 1901. The goal was to reduce the area of the mapped hydraulic records note floods much larger for 100-year flood zone along Ashley Creek the size of their drainage area than else­ downstream of the point where canals had where in the state. The high flows and rapid been constructed near Maeser to handle excess rises in narrow mountain gorges create a more water from the creek. The area as originally severe flood problem than that found in most mapped contained 525 homes and 25 businesses, other areas of the state. and the construction of 10-15 homes a year was projected. The numbers will be somewhat Also in contrast to the problems with smaller for the reduced area. FIA records flows emerging from mountain canyons in most show that one dwelling policy for $35,000 had other parts of the state, the principal been sold by May 31, 1979. Interviews with sources of flooding in Washington County are Uintah County officials in late 1978 indi­ the Virgin and Santa Clara Rivers and Fort cated that seven dwelling and one commercial Pierce Wash. High flows in other normally policy had been sold for an approximate total dry washes also cause occasional problems. face amount of $167,000. Flooding may be caused either by general rain coupled with snowmelt or localized summer Information obtained from county of­ cloudbursts. The flood of December 1966, f icials indicated that the canal structures which produced 100-year flows on the Virgin

61 River, was caused by heavy rains that washed 197.3). These two months are the primary flood away the winter snowpack. seas.on. The area around St. George is rapidly developing as a ret irement and vac"'- ion Flooding on the tributaries to the communi ty. Much of th is development has Virgin River is usually caused by localized occurred on floodplains because the terrain summer thunders torms • Peak f low on For t is some of the most conducive to construction Pierce Wash in the August 1971 flood was in the area. The pace of growth has not estimated at 15,000 cfs, about three times slowed since commencement of the federal the peak flow on the Virgin River for insurance program. Thus, a flood of magnitude the same flood; but in December 1966, Fort equal to that in 1966 would now cause far Pie~ce Wash had a peak flow of only about more residential damage. 1,000 ds. Most of the construction in flood-prone The Ash Creek, K.olob" Upper and Lower areas, however, has occurred in incorporated Enterprise, Pine Valley, and Gunlock Reser­ towns and cities. As land is converted to voirs, all constructed with state and 19cal residential use, it is usually annexed into funds in the mountains north of St. George, one of the existing cities. The Bloomington provide incidental storage for protection Ranches subdivision is the major exception, against snowmelt runoff, but they are not with the lots on Sugar Les Road, between op~rated for flood control. The Soil Con­ Ch ur ch ill Dr i ve on the sou th and Th ree Bars servation Service's Warner Draw Project, Road on the north (approximately 115 acres) authorized in 1969, contains features for within the IOO-year Virgin River floodplain. flood damage reduction in squthern Washington Only 19 homes were located in the flood County. Structures include, 11 debris basins hazard zones in the unincorporated portions and 6 miles of divers ion channels. Proposals of the county in 1975 according to its for additional work around St. George and on application for the flood insurance program. Frog Hollow Wash south of Hurricane are being County officials seem generally aware of, but reviewed. In addition, several farmers have somewhat indifferent towards, the flood undertaken channel stabilization measures on insurance program. their own initiative to protect their fields. The Virgin River has a drainage area of about 6,000 square miles; 3,880 square miles The county has sought federal assistance of the bas in lie above Bloomington. Accord­ from the Corps of Engineers and the Soil ing to the Corps of Engineers study (1973), Conservation Service for structural flood the IOO-year flood flow at this point would control for the Virgin River, but these be about 46,000 cfs. Fort Pierce Wash drains agencies are reluctant to sponsor structural 1,660 square miles, with an estimated measures in the wake of the environmentalist 100-year flow of 24,000 cfs. The 545 square opposition associated with the woundfin mile drainage of the Santa Clara River would minnow controversy that: arose in debates over produce a 100-year flood flow of about 26,000 the Bureau of Reclamation's Dixie Project on cfs. These flows are somewhat higher than the :Virgin. Nonstructural measures, on the the 100-year flows obtained from the USGS othe~ hand, do not alleviate the main flood frequency studies and reported in Table 3 as problem, which remains crop and road damage caused as much by erosion ,and sedimentation 34,660 cfs for the 5090~square mile drainage area for the Virgin River above Littlefield, as by the flood water. Land use in the map­ Arizona, and 13,220 cfs for the 338-square ped flood hazard area is primarily range and mile area for the Santa Clara River above cropland. The more serious flood severity Santa Clara, Utah. Record flows at these two mak€~ flood proofing generally less effective points are 35,200 and 6190 cfs respectively. here than elsewhere in the state. The envelope curve of Equation 1 reads a flow of 18,800 cfs fo~ the Santa Clara River. The riverine nature of the Washington The December 1966 floodcon the Virgin River County flood problem matches the emphas is of was estimated by the USGS as a ,lOO-year event the national program more nearly than do the and also falls on the envelope curve as the sitl,lations elsewhere in Utah, but there are largest flood ever generated by a bas in of still important differences. For example, that size in Utah. One would have to con­ the high sediment content of the flood water c lude from the magnitude of ,these flows that greatly increases the damage caused by a Washington County has at least one of the given depth of inundation and makes actuarial most severe riverine flood hazard situations rates estimated from national data too low in the state in terms of depth and velocity (Grigg and Helweg 1975). It also increases of flooding and property at risk. the. importance of land treatment for flood control and suggests differences in flood Reports of flood damage in the area proofing design. While the cou.nty has joined began shortly after the earliest white the Nat ional Flood Insurance Pr.ogram to make settlement. In addition to the flood of its citizens eligible for insurance, its record in December 1966, winter flooding also nonstructural program has been minimal. occurred on the Virgin River in 1911, 1932, County officials apparently do not see the 1938, 1958, and 1969. General summer rains danger as very great, and their assessment produced the most recent floods in September is supported by having experienced a 100-year 1972 and August 1971 (Corps of Engineers flood in 1966 with minimal losses.

62 Findings for Towns and Cities invest igat ion was cont inued because of the town's interesting flood hazard situation. -- Beaver Southeastern Utah has had a history of Beaver was selected to represent towns repeated flash floods over the years. The with between 1000 and 5000 people that have 70,000 cfs recorded on the San Juan River at not entered the flood insurance program even Bluff in September 1927 is the largest flow though a hazard h~s been identified. In June ever recorded on any river in the state. 1974 four blocks at the southern end of the Other problem areas are Comb Wash and Cotton­ town were designated as within the 100-year wood Creek near Bluff and the Montezuma Creek f loodpla in of the Beaver River, wh ich flows on the Navajo Indian Reservation. In all approximately 100 yards south of the city. these cases, heavy summer rains swell creeks City officials contend that there is no flood and washes with the onrush of water, silt, hazard within the city, although they recog­ and boulders. The floods of 1963, 1968, and nize the hazard posed by the Beaver River in 1970 were particularly troublesome for the county and have refused to join the FIA residents in Bluff. Peak discharges of program for this reason. Their appeal Cottonwood Creek at the Highway 95 crossing of the flood hazard designation succeeded in west of Blanding and at Bluff were 20,500 reducing the designated area to a half-block cfs and 42,100 cfs, respectively, in the 3 feet lower than the surrounding land, August 1968 flood. The peak discharge and having poor drainage. City officials do in Comb Wash near Bluff of 8,390 cfs was not regard the periodic inundation of this three times that of a 50-year flood. The half block from rainfall as a flood hazard flows backed water 3-feet deep into Bluff and because no damage is done by the standing caused over $16,000 in damages to business water. Moreover, the fill required to raise and residences (Butler and Marsell 1972). t he land high enough for highway access, should development be desired, would elevate Record breaking rains in early September the area above the level of the FIA desig­ 1970 produced flash floods which destroyed nated flood. An FIA review will be conducted roads and bridges and damaged several ranches in the near future to determine whether the near Bluff, Montezuma Creek, and Aneth. map should be rescinded. Considerable damage was done to Navajo Trust Gardens. Two people were drowned when they Butler and Marsell (1972) record six drove their car off a washed-out bridge. cloudburst floods in the area of Beaver New 12- and 24-hour rain measurement records between 1939 and 1969. Woolley (1946) for the state were set by the storm. Damages recorded six spanning the period from 1882 to to roads, bridges, and farm buildings were 1937. All the reported damage seems to have estimated at $165,000. been to roads and farms near the town (except for the distruction of a brick kiln in the Interviews with San Juan County of­ South Mountains in 1882), and no mention is ficials and residents of Bluff indicated made of flooded buildings. The largest flood that they see the main problem as caused by in 51 years of flow records on the Beaver high flows in Cottonwood Wash. Debris River at Beaver (82-square mile drainage lodges against the Highway 163 bridge and area) was 1080 cfs on July 22, 1936. Th is backs water into town. The August 1968 flood compares with an estimated 100-year flood of backed water onto the school yard and a loc~l 1370 cfs. The regional flood envelope market along Highway 163. curve (Equation 2) gives a flow of 3600 cfs. Since Bluff residents voted to dis­ Even if FIA does not rescind the Beaver incorporate, property owners in the community flood hazard map, the town would suffer very are able to purchase insurance because little cost in implementing a floodplain San Juan County is a participant in the FIA management program for its half-block of program. However, few Bluff res idents who lowlands and make all 1750 residents eligible have experienced flood damage were found to for flood insurance shpuld a very extreme know about the subsidized insurance program riverine flood occur or should localized or understand that San Juan County parti­ cloudbursts send water through town in lesser cipates. To date, no insurance policies have washes. Expansion by incorporation to the been purchased by the 7320 residents of the northwest or the south would bring flood county's unincorporated areas. prone land into the town, and such an even­ tuality should cause the city to join the Bountiful insurance program. Bountiful is a community in the 5,000 to 50,000 range for which a detailed study was Bluff underway at the time the sample was taken and which is now in the regular program. The Bluff was selected in the sample to city is situated on outwash alluvial fans represent towns of under 1000 populat ion downstream from the mouths of Barton, Mill, not mentioned as to status in the list of the and Stone Creek Canyons. These creeks flow flood insurance program. While it turned out through the city from east to west in rela­ that the reason for this omission (and tively steep channels and flood narrow omission from Table 10) was that the village str ips of land already fully developed with had recently voted to disincorporate, the housing and other buildings.

63 Storm drains constructed by the city highway). The 36-inch conduit is being.en­ discharge local runoff into the streams larged to a 72-inch conduit by the county in at various locations. This was considered an coop,erat ion with the State Highway Depart­ appropriate approach to storm drainage until ment. the early 1970s when West Bountiful began to object because flows were being increased Storm sewers were first installed under downstream in that city. Channel capacities the city streets 80 to 90 years ago, and some are less and the floods spread over a wider are now inadequate. Others have collapsed area when they reach West Bountiful. The and been replaced. In 1978, the city re- damage potent ial is also being increased as placed two sect ions. one on 4th east and 6th urbanization moves westward. south and one on 3rd south and 2nd east. Bountiful and West Bountiful have a long More sections will be replaced as money history of flooding. According to the Corps becomes available. The job is estimated to of Engineers (1969), "Sketchy accounts by cost $1,500,000, and the city expects to early settlers, brief newspaper articles, and spend $50,000/year. of f icial r,ecords indicate that flooding occurred on Barton, Mill, and Stone Creeks in Frequently, storm sewers fill up and 1862, 1896, 1922, 1923, 1930, 1936, 1950, over flow. At other times, they are clogged 1952, 1958, 1962, and 1969. No hydrographs from sand washed off the mountain sides. of past floods are available." Butler and Keeping the storm drains cleaned is a major Marsell (1972) note 12 cloudburst floods in maintenance problem for the city. The city Bountiful between 1939 and 1969. Several uses its street crews to clean all storm thousand dollars in flood damage occurred to drains prior to the pavi~g season in the homes from flash flooding August 5, 1948. A spring and again after the paving season in much larger amount occurred July 27, 1951. the falL Homes were again inundated August 4, 1954, by water and mud reaching 3-foot depths. Many In 1971 a law suit was entered against homes were flooded by Stone Creek May 20, Bountiful by West Bountiful in district 1957. On June 24, 1969, flood water 2.5 feet court. The suit sought to prevent Bount iful deep' was reported in a business establish­ from discharging storm water into creeks as ment. The last major snowmelt flood occurred had been the practice. The judge ruled, in 1975 when high spring runoff in Mill Creek however, that as long as the drainage came caused extens ive damage in West Bount ifuL from within the basin it could be discharged While no explanation was obtained for the into the streams. . differences in dates between these two flood histories, frequently occurring substantial flood losses to buildings are obvious from In total, three cities to the west are subject to flooding from runoff that origi­ both. nates in or goes through Bountiful. Bountiful Bountiful has an active structural flood officials feel that Davis County is headed in control program. In the last 10 years, the the; right direction with its countywide city has spent over $2 million. Most of the flood control program. The county program 25-30 projects collected local storm runoff uses funds from a 2-mill property tax levy anel discharged it into one of the three to provide f loodways carry ing water to the creeks. Because larger systems would be too Great Salt Lake. Trunk lines to the flood­ expensive, the designs generally have been ways are provided by the municipalities. for a 10-year return period. The increased runoff caused by upstream urbanization and '\I ~A detailed flood hazard study has been their new storm sewer systems are, however, cOllip'ieted by FIA for Bountiful, and the flood contr ibut ing to the downstream problem. insurance map and ordinance have been adopted Bount iful was the first community examined by the city and put into effect. Actuarial having urbanization covering a sufficiently insurance rates are now in effect for second large portion of its total watershed area for layer coverage. However, the City Engineer, this to occur. when interviewed, said it was his feeling that the rates are so expensive that not many To counteract the problems caused by people will buy the insurance. A total of 40 larger flood peaks, Bountiful has constructed policies providing $1,285,000 in coverage several small detention basins. One is were outstanding as of May 1979, but it is on Mill Creek at Bountiful Boulevard (4 ac). not known how much of th is is second layer Another is under construction on Mill coverage at the actuarial rate. Creek at Davis Boulevard (5-6 ac). The city also ha;> cooperated with West Bountiful, The two areas in the Bountiful flood­ Centervi lie, and Davis County in a project plairi selected for field observation were 1) rerout ing Stone Creek from the west boundary Mill Creek between 100 East and Orchard of Bountiful to the bay and is working Drive, and 2) Barton Creek between 200 East to correct the flooding problems at the lower and 400 East. Land use in the Mill Creek ends of Mill and Barton Creeks. area consists of an athletic field, parking lots, and housing. Flood damage potent ial Flooding from spring runoff on Barton appears to be minor except for backyards and Creek has been aggrevated by water backed up baiements of eight houses ($75,000 class) by a culvert at 4th north and 2nd west (state along the south side of Mill Street.

64 Land use in the mapped 100-year flood­ the opportunity for infiltration that quickly plain between 2nd East and 4th East and attenuates flows spreading out over an between 2nd South and 4th South on Barton alluvial fan. Storm drains that convey Creek. (see Figure 11) is primarily residen­ water from throughout the urban area to the tial, but existing buildings include a day stream concentrate flows that would otherwise care~enter, a medical center, and a nursing never add to the flows emerging from the home. About 40 homes averaging $50,000 in canyons. Instead of the flood peaks emerging value would suffer basement and first from the canyons being dissipated, they floor flood ing in a 100-year event. The increase in size. Communities too far from three nonresidential buildings, estimated to the base of the mountains to experience have a total value of several million, would flooding under natural condit ions can be also be expected to suffer basement and first subjected to a severe flood problem. Th is floor flood damage in a 100-year flood. may well be the most severe secondary impact of structural flood control measures in Corps' hydrologic studies indicate that Utah. Barton Creek has a drainage area of 5.6 square miles and a 100-year flood of 420 cfs. Some ent ity needs to look at th is The small drainage basin size explains problem from the viewpoint of the total why urbanization can have such a large effect storm water system. Individual communities on flood flows, and the degree of urbaniza­ do not have the resources for this sort of tion which has already occurred may cause the analysis and do not have the authority to 100-year flood to be larger than indicated by solve problems outside their jurisdictions. an envelope curve based on recorded flows A centralized review function to check from natural basins. community storm water control measures for adverse effects on those downstream may be The Bountiful situation brings out very helpful for areas where many communities another aspect of the Utah flooding problem. abut one another in a metropolitan area. Urbanization is well known to increase downstream flood peaks in humid climates, and Castle Dale the effect is much more severe in arid areas (James 1965), Paving over dry desert soil This community was selected for inclu­ can increase runoff from practically nothing sion in the sample to represent towns to nearly 100 percent. Levees that conf ine under 1000 that had entered the emergency streams within narrow bands greatly reduce program and had a detailed study underway for early entry into the regular program. 'The results of the detailed study have since been reported back to the community, are under review, and may possibly be appealed. Woolley (1946) reports cloudburst floods near Castle Dale in 1913, 1930, and 1933, and Butler and Marsell (1972) report 7 cloudburst floods between 1939 and 1969. The flood of July 12, 1933, flooded gardens; however, only the storm of August 8, 1957, is reported to have flooded homes, and it is not clear from the reports whether that flooding was in town or not. The increase in population for the town from 541 in 1970 to 861 in 1975 shows how energy resource development in the area is causing growth in a previously sparsely populated section of the state. That growth 100 YEAR FLOOD can be expected to continue and aggravate pressures for floodplain development in and (SHADED) near the town. The mapped flood hazard area within Castle Dale is along the portion of Cotton­ wood Creek which runs along the southwest boundary of the city. Additional flooding has occurred in Buckhorn Draw and along the San Rafael River east of town. There is no development in the flood zone in the south­ west port ion of the town because of a high water table situation. The southeast portion cannot be developed because a sewage treat­ ment facility is being constructed down­ Figure 11. Flood hazard on a segment of Barton stream, and EPA requires a certain d is­ Creek in Bountiful (from FIA de­ tance separating the plant from residential tailed study, 1978). development.

65 Whlle Castle Dale participates in the Ea.st. Layton Nat IOnal Flood Insurance Program and has passed a floodplain management ordinance, East Layton was also selected from.among town officials are vague as to the city's the. communit ies under 1000 in the emergency responsibility under the program. Only one program. There are no recorded cloudburst flood insurance policy is in force. The floods and have been no recent flood lng concept of floodplain management has not had problems other than those caused by ruptured much impact on planning in the community. In pipelines and canals. Streams pass through order to prevent continued growth from the community in well-defined drainage chan­ infringing on high risk areas, officials of nels. Most flood waters from the mountains to the national program will have to do a better the east flow into the well-defined channels job of convincing local officials that it is and cause no flood damage as they pass in their interest. through town. Corinne City officials were briefed on the National Flood Insurance Program by,FIA Corinne was selected from among com­ personnel in April 1978 and joined after munities of under 1000 in the emergency being sat isfied that they will be given program. The town of 486 is located near the opportunity to review and comment on the maps Bear River far enough back from the Wasatch that are now being prepared in the detailed Front not to have to worry about flood flows flood hazard study. Some officials com­ emerging from the mountain canyons. No flash plained that the preliminary flood hazard flood problems are ment ioned by Woolley maps are not sufficiently detailed and (1946) nor Butler and Marsell (1972). No undated to be useful in conSidering annexa­ flood frequency analysis was made on the 90 tion requests in this growing urban area. years of gaged record on the Bear River They state, for example, that RainbOW-Drive, sligh tly upstream at Collinston because the which is shown as in a flood hazard area on f lows are so greatly regulated by upstream the FIA preliminary map, does not now have a irrigation and power reservoirs, but the flood hazard because a larie storm drain has highest recorded flow at 11,600 cfs occurred been installed by the city. Since storm June 7-10, 1909. That flow is fairly drains are customarily designed for the 10 close to the 9,700 cfs Equation 2 gives for rather than the 100-year event, this may well the 6800-square mile drainage area. The bean overly optimistic interpretation of the population of the community has changed drain's effectiveness. Although housing is little for many years. being developed along Mill Creek, the channel is deep and the houses are on high There is no record of any flood damage ground wIth no flood hazard. being caused by the Bear River in the town in East Layton has much more to ga in than the over 100-year history of the community. does Corinne from entry into the program The completely undeveloped wetlands along the because of the greater hazard and hydrologic river shown to be in the 100-year floodplain uncertainty associated with being closer to by the preliminary FIA map are generally the base of the mountains and in an urban conceded to have no development potential. growth situation. The community, however, None of the higher ground where t he town lies does not seem to have the expertise in is considered to have a flood hazard, and no floodplain management necessary, to realize one in the town has purchased flood in­ those benefits, and this may suggest a role surance. Except for the very slight security where the state can help. being in the program could bring town residents by making them eligible to purchase Garden City insurance against very rare or local events and the insurance the floodplain management This community was selected as one of regulations provide against foolish future those having less than 1000 people and not development of the wetlands, entry into the ment ioned as to flood insurance program program has not benefited Corinne. However, status. Garden Ci ty is located on a rela­ since the program has also had almost no t ively narrow flat strip along the shores of cost, the slight benefits may be sufficient Bear Lake with mountain slopes rising steeply to have made entry worthwhile. In December to the west in back of the town but with no 1979, Corinne was shifted to the regular pro­ drainage, except from very small h ills lope gram under the special conversion provisions. areas, passing through town. Since most Utah storms move from west to east, the incidence This study did not probe into why of recorded cloudburst floods is much less Corinne chose to enter the program when for communities like Garden City on the it does not have a significant flood hazard leeward side of the mountains than it is for whereas other communities in the sample the Wasatch Front communities where oro­ declined. Perhaps the reasons relate to the graphic lifting augments precipitation on the psychology of being a river town as opposed windward side. Based on this topography and to being in a location more remote from a the fact that the town has absolutely no water course and where talk of flooding history of flooding (Butler and Marsell consequently sounds more ridiculous. A 1972), the community has not received any second reason could be the complete lack of attention from FlA. When interviewed in the interest in the community of future develop­ fall of 1978, the mayor was not familiar with ment of the declared floodplain. the FIA program.

66 The development trend in the area does, owners in that residents of the flood free however,lhreaten a significant future area immediately outside the city limits are hazard. Large numbers of cabins and condo­ eligible to buy security against flooding by miniums are being planned and built on rare events because the county is in the hillsides above town for Bear Lake recre­ program. alionists. As vegetation is removed from hillsides, more mudslides and other flooding Helper problems are ant icipated. The problem will be most intense during the construction Helper is a town in the 1000 to 5000 pe r iod, but the higher runof f from paved population range with a detailed study areas being discharged down the mountain completed in September 1978. The city is slopes can be expected to create a continuing subject to flooding from two sources. The problem. A planning and zoning board was Price River flows from north to south through established in 1978 by the city to deal with the center of town. Spring Canyon Wash flood hazard and other problems related enters the city on the west, curves to the to development. Some minor problems with north, and empties into the Price River runoff down the mountainside are being just north of the Main Street bridge. handled by diking by individual property owners. The population of Helper declined by 20 percent in the decade between 1960 and 1970. Thus Garden City is an example of a Since 1970, however, the city has been community with a potential threat of flood growing at a rate of about 2 percent per damage to res ident ial and commercial bu ild-:­ year, spurred by the increase in coal mining. ings but for which the FIA program has Growth pressure is likely to remain high for offered no real help. The state may have an some time. With the exception of several important role in helping communities too acres on the city' s southern boundary, most small to be ef fect ive in such situations on of the floodplain lands within the city their own. limits have been developed. Garland Hazard zone deSignations for Helper were made in January 1974 and revised in January This community was selected to represent 1976. The city entered the emergency program those in the population range from 1000 to in June 1975. In 1976, FIA contracted with 5000 and not mentioned in the National Flood Nielsen, Maxwell & Wangsgard/Montgomery to Insurance Program. The community sets carry out a flood insurance study for Helper, between hills rising to the west and the Price, and Carbon County. The work was deeply entrenched Malad River to the east. completed at the end of 1977, and a review On September 1, 1919, a cloudburst sent a meeting was held in April 1978. Helper "wa ist deep stream of water" roar ing down a entered the regu lar program in September hillside a few miles north of town covering 1978, but was suspended after 6 months time many acres of farmland with mud (Woolley when FIA determined the city's floodplain 1946). Even though there is no current or management ordinance to be inadequate. The historical evidence of flooding actually in problem was disagreement over the approach this city since its founding in 1902, a large used by the city in restricting floodplain but undeveloped portion of the, town was shown development rather than over object ives. to be prone to flooding from sheet flow off A revised ordinance was submitted an~ re­ the h ills to the northwest by the flood ceived FIA approval in August 1979. hazard map FIA released to the town in October 1976. The map was rejected by the The flood insurance study indicates a City Council, appealed, and rescinded in drainage area of 465 square miles for the 1977, a decision implying that no hazard area Price River above the confluence with Spring exists in the town. The flood hazard Canyon Wash. The latter has a dra inage boundary map for adjacent portions of Box area of 24 square miles. The 10-year and Elder County released in February 1978 does 100-year flood flows estimated in that not show the mapped 100-year floodplain study for the Price River are 3,736 cfs and anywhere in the city limits. 10,208 cfs, respectively, and for Spring Canyon Wash the estimates are 887 cfs and According to these maps, the community 4,378 cfs, respectively. The USGS frequency has been found free of flooding by the analysis of the gaged record for the Pr ice 100-year event; but because Garland has not River near Heiner (455 square miles) indi­ joined the program, its residents are not cates a 100-year flow of 7150 cfs and a eligible to buy flood insurance against record historical flow of 9340 cfs on Septem­ inundation by rarer or unanticipated sources ber 13, 1940. The envelope curve for the of flood water. It would be advantageous for Colorado River Basin (Equation 1) shows that the community to obtain a program status flood peaks from this size drainage basin that would permit its residents to take have reached 20,000 cfs. advantage of the low flood hazard by becoming eligible to purchase insurance based on Woolley (1946) records that eight houses actuarial rates for zone C areas, parti­ in Helper were filled with mud and debris on cularly in light of the uncertainties in July 29, 1921, causing $5,000 in damages. floodplain mapping in desert areas. The Cellars were filled with water and several present situation is inequitable for property buildings settled several inches from flood-

67 109 In July 1927. Butler and Marsell (1972) 1:9:72). The bridge at Peach Avenue was washed record fIve flash floods affecting Helper downstream and lodged against the next between 1939 and 1969. They note the 1940 bridge, forcing water to flow over the banks. flood as flooding several homes in Hel~er and No specific mention of flooding in the wash suggest that a larger event occurred in on the northeast was found. 1908 (before stream gage records begin). On August 5, 1943, a flood apparently origi­ Like other towns in southeast Utah, nat ing from Spr ing Canyon "wrecked houses, Hurricane is growing fairly rapidly; the railroad lines, mine properties, garages, and aqnual growth rate exceeds 4 percent. bridges" to an amount estimated at $75,000. Undeveloped land outside the floodplain On August 8, 1947, heavy rainstorms in town is still extensive, and most of the flood­ caused flooding from the overflow of ditches plain land is idle or devoted to agriculture. and canals. The most recent flooding on the Nevertheless, several newer homes have been Pr ice River occurred on July 4, 1977, when built along Gould Wash, and it seems reason­ ext ens ive damage occurred on the Carbon able to expect the demand for further con­ County golf course south of Helper. Apparent­ struction to continue. ly, there was little damage in town. Hurricane entered the emergency phase of The Scof ield Reservoir, in the upper the insurance program in June 1975, and FIA watershed of the Price River, controls published maps of the flood zones in July snowmelt flooding, but does not provide much 1977. No detailed study has been scheduled. protection against cloudburst floods. Entry into the flood insurance program No other flood control structures have been has not had a significant impact on the built on the Price River or Spring Canyon economy of Hurricane. City officials recog­ Wash. Flooding on Spring Canyon Wash can nize the potential flood hazardS in the area, occur from relatively minot storms as and therefore support the concepts of flood­ accumulated debris obstructs flow through p la i n man age men tan d flood ins u ran c e • bridges. Residents do not view flooding as a major Land use on the Pr ice RiVer floodplain concern, and have been slow to purchase in Helper is mixed commercial and residential insurance (only one policy in effect). The on the north and residential towards the newer floodplain residents have not experi­ south. Development has proceeded southward, enc.d flood damages, and the older residents with newer and larger homes further south. A are content to deal with damages when they subdivision was proposed on the last remain­ occur. ing open tract on the south, but the plans Planning studies ha~e examined Gould have been withdrawn by the developer. The Wash for sites for potential flood control chairman of the Planning and Zoning Commis­ structures. The structural detention of sion indicated that floodplain regulations sediment and water upstream from town may be were not a major consideration in the with­ economically justified, but it would be very drawal, although approximately one-third of difficult for the federal government to the tract lies in the regulatory floodway. implement a flood control p~oject in the area Land use along Spring Canyon Wash is pri­ given current planning delays and budgetary marily residential and commercial, with restrictions. Financial assistance to small several acres of idle land in the area towns in such cases may be another potential adjacent to U.S. Highway 6 and 50. Structures s tate role. in the area are at least 20 years old, and no new construction was observed. The flood Hyde Park insurance program provides a valuable finan­ I' cial resource for a community like Helper This Cache Valley town was selected as a where a great deal of older development member of the emergency program in the 1000 already exists on a riverine floodplain and to 5000 population range. In December 1979, is known to have suffered periodic damage in Hyde Park was shifted to the regular program the past. und'er the spec ial convers ion provis ions. According to the mayor in August 1978 and Hurricane as confirmed by Woolley (1946) and Butler and Marsell (1972), there is no history of flood­ Hurricane in Washington County was ing in Hyde Park. According to topographic selected from among the towns in the 1000 to maps of the area, the small streams emerging 5000 population range with membership in the from the hollows and canyons onto the still emergency program. The flood hazard is steeply sloping valley floor about 2 miles largely associated with Gould Wash on the east of town are intercepted by three paral­ southern boundary and another wash in the leI 'irrigation ditches. One flows about a northeast part of the city. quarter mile up the hill from town and the other two flow through the town. The Gould Wash, the larger of the two, entire town is built on a fairly steep presents the greater flood hazard. Flood slope downward to the west. waters from the wash filled 7 basements on July 27, 1954, and large amounts of silt wete The flow from Hyde Park Canyon is washed' onto a large area 8 days later in what d Lrected so as to flow into the northeast the Deseret News called "the worst flood in corner of town, and a small atea in that part the history of Hurricane" (Butler and Marsell of town is shown to be in the 100-year

68 floodplain by the flood hazard boundary map. Kingston Inspection of this floodplain area revealed three dwellings in the $60,000 price range Kingston was selected to represent and about 40 acres of hay. One of the communities of less tban 1000 people where a dwellings looked low enough to be in parti­ flood haz~rd area was mapped but which cular hazard. subsequently declined to enter the emergency program. The flood problem in the community The drainage area tributary to the mouth is associated with the east fork of tbe of Hyde Park Canyon of about 4 square mi les Sevier River as it makes a series of bends could, according to Fletcher, generate while flowing northward from the southeast a 100-year flow of 530 cfs. Equation 2 gives (from Kingston Canyon) along the .eastern a flow of 1820 cfs. The canals are far boundary of Kings ton. Cons iderable debr is enough back from tbe mouth of the canyon for and .trees clog the river channel, and beavy much of the flow to be dissipated before rains flood bordering alfalfa fields. Some reach ing them, but there is danger of flood hay harvest loss has been experienced. waters causing a full canal to break, perhaps The floods bave apparent ly not reached the at some point otber than wbere tbe flows mobile homes on the bigher east bank of the enter. While tbe probability of any flow river. reacbing ''the canal is relatively low, tbe canals would largely determine the Table 3 shows the 63 years of record on floodi ng pat tern during the 100-year flood. the east fork to suggest a 100-year flood Minor modifications to the canals could peak of 1839 cfs from the 1250 square mile possibly reduce the flood risk in Hyde Park drainage area. The envelope curve value further. (Equation 2) is 6600 cfs. Butler and Ma~sell (1972) record a 4-foot wall of water moving Kamas down Kings ton Canyon on August 6, 1967, closing Utah Highway 22 for 6 hours, but Kamas entered the sample representing mention no flooding of buildings. The record towns with membership in the emergency flood on the river at Kingston was 2030 cfs flood insurance program and under 1000 on May 12, 1941. population. No cloudburst floods are listed as baving occurred in the vicinity of the The reason one official suggested for town from 1939 through 1969, and the princi­ the town declining to apply for the FIA pal flood hazard is along Beaver Creek wbich emergency program was a feeling that the flows through the town in a northwesterly sor ts of damages experienced are not in­ direction. Several historical floods have surable under the program. Th is d iscount­ overtopped the streambanks and inundated ing of the riverine flood problem is also small acreages of cropland, but no documented seen in that the town is unwilling to budget damages have occurred to residences or other funds to clean the river channel of debris. buildings. The problem has been discussed betweenPiute County officials and the U.S. Soil Conser­ Upon receiving their flood hazard vation Service, but nb plan of action has boundary map, Kamas applied for inclusion been prepared. in tbe emergency program but did so under a protest claiming that the 100-year floodplain Koosharem is smaller than mapped. The appeal stated that even tbough Beaver Creek runs tbrough Koosharem is a town of under: 1000 that the middle of town, no structures are in the has elected not to join the program even floodplain. Four long-t ime residents filed t hough a flood bazard has been ident ihed. an affidavit contending no known flood damage The mapped hazard area shows a 100-year to structures had been experienced in over 70 floodplain fanning out from where Koosharem years including during the heavy snowmelt Creek emerges on to the floor of Grass Valley runoff and rain year of 1975. When the town and covering most of the town. The flow entered the program in 1976, the previously enters Otter Creek east of town. Butler and mapped hazard area along Beaver Creek through Marsell (1972) record no cloudburst floods the town was eliminated, and the only mapped in the area, but Keetch (1971) and Woolley floodplain left was east of town where little (1946) record that a cloudburst caused a development has taken place. Since then, severe flood on Otter Creek July 12, 1896. five policies have been sold. Koosharem is apparently a town with some Two issues arise in evaluating the risk of flooding but a long time since the effect iveness of the Kamas program. These last flood. Older citizens indicated that in are whether the hazard area has been ade­ their 70 plus years they had not witnessed a quately mapped and what pressures exist flood in Koosharem (tbe last recorded one was to develop the remaining mapped flood hazard in 1896) even during the heavy rainstorms zone. Tbe stopping of desirable develop­ which occurred in 1965,1967, and again in ment would be a significant cost of flood­ 1968. They also claim that flooding has plain management for tbe community. The fact never been a problem in the floodplain mapped that five policies have been sold even though along the Otter Creek. Grazing capacity few structures are in the mapped floodplain is reduced by early spring excess water but suggests worried citizens outside the of­ dwellings near Koosharem have not received ficial hazard area. damage.

69 The drainage area of Koosharem Creek, -. which flows from the west into Koosharem and then into Otter Creek, is approximately 20 Midway represents communi ties of under square miles as estimated from available 1000 population in the emergency program. In topographic maps. Peak discharge for the the only part of the town mapped in the 100-year flood would be less t;:han 2600 ds lODe-Year floodplain, an area along Snake according to Equation 2. Creek near the western city boundary, there has been some flooding of cropland but no one Koosharem and Sevier County officials was found who could remember any flooding of met to discuss the FIA participation issue at structures. Butler and Marsell (1972) record the time Sevier County made application. no cloudburst floods in or near the town and County officials took the necessary steps to only one in all of Wasatch County. Woolley enter the program in 1975, but Koosharem (1946) records flooding in the Heber City officials did not apply until April 1979. area io 1887, 1894, 1896, 1925, and 1935 but FIA has not approved the application, pending no damage to buildings. a more complete documentation. Officials of Midway appealed the flood Koosharem experiences long periods of zone boundaries designated in 1975 on the time between floods. Hydrologically, most basis that storm water ponding rather than runoff from Koosharem Creek apparently flood prone areas were shown for the Devil's percolates underground before flows from the Hole drainage. A boundary revision in canyon reach the town. Usually, any small October 1975 deleted the disputed area. The flow remaining is intercepted by an iniga­ remaining mapped 100-year zone is a 100-foot t ion canal. Only for events in the order oJ wide strip along both sides of Snake Creek. the IOO-year return period does enough water NO structures were indicated as being in come out of the canyon to flow overland this area at the time the revision was made, through town, and by the fortunes of history but some sheds have apparently been built no such event has occurred for more than 80 there since. One insurance policy has been years. issued to date. Virtually the whole town is in a border­ Miilville line flood hazard situation. Flows emerging from canyons onto alluvial fans spread out Millville was included ,in the sample as and percolate until they dissipate and a :community of population under 1000 where become harmless. The rarer floods travel the hazard was ident if ied but the community further down the fan before so dissipating. elected not to join the program. The town is Koosharem is located far enough down the fan located in Cache Valley on the alluvial fan for it to be difficult to tell whether it is formed by flows out of Providence Canyon and upstream or downstream of a line where the about I mi le west of the base of the moun­ 100-year flood is dissipated to harmlessness. tains. The flow from Providence Canyon D i ff icult ies in the determinat ion stem from passes far enough to the north to pose little the lack of a precise definition of the danger, and the hazard to the town now character ist ics of a flood reduced to harm­ comes from two small hollows that discharge lessness, uncertainties in estimating the their occasional flows opposite the town and 100-year flow for an ungaged stream, and from Millville Canyon that discharges far inadequate ground information for routing enough to the south to almost entirely miss shallow flows through areas where irregu­ the town (Gingery Associates 1976). The l~rities in the ground surface only a fe~ greater problem from that source may be that Inch~s high can have a major effect in theolillville-Providence irrigation canal d.iverting the flow. could intercept flood flows from the canyon, carry them to the north, and break opposite Institutionally, FEMA considers the town the town. The west side of the town abuts to be on a floodplain. While the subsidized ag'ainst Blacksmith Fork, and lowlands rates available through the emergency program along that river are subject to flooding from would be attractive to Koosharem home owners, that source. actuarial insurance rates would probably be hIgher than the expected average annual The only flood this century for which damage. Unless th is can be successfully any damage was recorded was that of August appealed (the experiences of other towns 18, 1959, when cloudburst rains sent waves of indicate good probability of success) water and debr is rolling down the mountain­ ent ry into the progr am may unduly restrict side aod littered bench areas below Millville the ability of the people to construct or Can'yon with boulders. No damages were noted replace buildings. then for structures in Millville even though such nearby communities as Providence faired The sit;:uation emphasizes the need for much worse (Butler and Marsell 1972, Gingery better methods for flood routing over al­ Associates 1976). luvial fans. Better methods would enable better risk assessment and provide a better Blacksmith Fork drains about 268 square basis for the design of measures to deflect miles. Gingery Associates (1976) estimated a flows away from buildings. This sort of 100-year flood flow of 4535 cfs. The USGS design could well be the most economical analysis of 62 yeats of gaged record gave approach for communities like Koosharem. 1825 cfs. The historical flood of record was

70 1400 cis on May 4, 1952. The envelope curve insurance in areas of real risk. The (Equation .2) nearly matches (4680 cfs) the FEMA concentration on riverine flood problems Gingery Associates figure. and failure to map flooding from small mountain hollows wash ing mud and debr is .The area flooded by 4535 ds is delirl­ into towns discourages participation in a eated in the floodplain informat ion study. town like Millville and misleads newcomers to It is a low area of pasture and wasteland the town as to the real danger. along the east bank of Blacksmith Fork. A small dike has been constructed along the bank to protect approximately 5 acres of pastureland. There are no structures on the floodplain. Certainly, if no Millville The second largest city in the state was structures are threatened by this very selected to explore flood hazard s ttuat ions conservatively estimated 100-year flood, the and responses to them in a city of 50,000 in town is in no real danger from flooding the emergency program. Ogden's problem of from Blacksmith Fork. The management question flood waters and associated sediment and on the west side of town is whether the town debris moving out of the mountains and really needs to regulate development in an needing to be transported through the city area as large as that delineated. to lowlands to the west is typical of Wasatch Front communities. The problems, however, The more important quest ion is whether are intensified by a larger city with greater the flood hazard mapping can be believed population density spreading over a larger where it shows the town to be in no danger of area. The greater deg~ee of urbanization flooding from the hollows and from Millville increases the contribution to flooding from Canyon (drainage area of 6 square miles) to local runoff from impervious areas, reduces the east. Whether the 100-year floods from percolation of water moving over the alluvial the east would reach town is, for the reasons areas and hence causes flooding to extend discussed for Koosharem, difficult to deter­ farther down the hill, and results in more mine; but, whether or not that frequency damage as flows pass through a more congested of flood would cause damage, larger events area. from this direction could be devastating. Prudent Millville residents might well want ins ur ance. For many years, Ogden residents have suffered recurring damage from both snowmelt The Mayor of Millville, when interviewed and cloudburst floods. Snowmelt flows in August of 1978, did not seem familiar with originating in Taylor Canyon east of the city the FlA programs, but he did indicate that have on occasion turned one of the east-west the town would have been interested in streets, 27th Street, into a river arid 'car­ joining if the whole town could have been ried large rocks and debris into residential and business areas. Yards and basements have covered by the insurance. He ~as incorrectly advised that the program would only cover the been flooded and sometimes buried in mud when undeveloped land next to Blacksmith Fork and these waters have not been contained within not flash flood damage associated with flows the street curbs. Cloudburst floods have out of the canyons to the east. The city has been more damaging and difficolt to cont,roi. thus taken the position that it wants no part Heavy storms occurring randomly at locat'ions of a program that will require it to undergo in and above the ci ty have caused cons ider­ the expense of establishing floodplain able damage and inc6nvenience through flooded management regulations to cover a portion of basements, land erosion, and sediment deposi­ town in little danger while offering no t ion. Woolley (1946) lists a number of insurance protection to structures that may floods beginning with a storm in August 1901 we 11 be in real danger. In December 1979, that filled basements, gashed streets, and the town was made eligible for special brought business downtown to a standstill. conversion to the regular program should it Butler and Marsell (1972) report 30 cloud­ enroll. burst floods or an average of one a year between 1939 and 1969. The smaller events Since the town is pr imadly basing its blocked streets and snarled traffic while the reject ion of the progr am on mis informat ion, ten or so largest ones washed debris irito the the state could well perform an important city and flooded basements. Depths up to 5 function by facilitating communications feet have been reported over yards and around between local governments and the Nat ional buildings. Flood Insurance Program. The problems cited in the floodplain mapping suggest a role for Ogden has recently been making an the state in reviewing floodplain information extensive effort to improve its storm studies for the reasonableness of the re­ drainage system (Hoggan and Nielsen 1979). ported results in Utah conditions. New detention facilities and pipelines are designed to handle aiD-year, 2-hour storm. Cases such as this, where the mapping The city officials consider this level of shows as flood free areas considered to be control to be financially feasible. In the flood prone by residents of the local com­ event of a more severe storm, the system's munity, have the effect of discouraging capacity will be exceeded and the city's precautionary flood proofing practice$ in east-west (downhill) streets will have building construction and the purchase of to carry the excess.

71 The ci ty has dealt with the problem of flood hazard study is currently being con­ continuing development further increasing ducted by FIA for Weber and Davis Counties. runoff by passing an ordinance in 1974 that This sort of change in the hazard situation requires all commercial development ov'er suggests a need for updating hazard mapping 30,000 sq ft and new subdivisions to provide and adjust ing actuar ial rates wi th changing detent ion to contain runoff from a 10-year watershed conditions and with expansions to 2-hour storm in excess of natural runoff. In the storm drainage system. Setting priorities Ogden, such a storm is considered to produce for needed updating may be another role 0.7 to 1.0 inch per hour of rainfall. The appropriate for state government. natural or preconstruct ion runoff rate is estimated from site conditions with a typical Four locations identified as having.a value of about 30 percent. Buildings and zone A flo,od hazard on the FIA maps da.ted pavement are considered to increase the rate August 16,1977" were selected for field to 95 percent. observat ion. These were located near: 1) Sullivan Road at Quincy, 2) 1100 North Street Although the city has not dictated west on Washington Blvd., 3} 2nd Street, specific designs or standards for developers at Washington Blvd., and 4) Ogden River in' to use in eomplying with this ordinance, two the vicinity of Washington Blvd. basic approaches have been used: 1) sumps to inject the water into the ground and 2) small The flooding potential in Sullivan detent ion basins to hold the runoff for Hollow (adjacent to Sullivan Road) between gradual release after the storm. Centralized Gramercy Avenue and Van Buren Avenue has been detention basins (up to 20 acres in size) are eliminated for events smaller than the 10- added by the city to reduce the size of trunk year with construct ion of a new interceptor lines. The designs of systems that inject drain along Van Buren in [978. A greater water underground need to be checked to make hazard remains on the north side of Sullivan sure that the recharge won't flow underground Road between Quincy and Van Buren. Approxi­ into basements or other problem-causing mately 20 homes ($50,000 class) there are loca t ions. subject to basement flooding. In October 1977, the city was awarded a The flood hazard area near Washington Local Public Works Capital Development and Boulevard in the vicinity of 1100 North is a Investment Program grant of $7.6 million from low weeded area surrounded by residences. the Economic Development Administration of Several old rundown buildings are located on the U.S. Pepartment of C;:ommerce. The major t he southwest fr inge of the mapped flood­ conditions of the grant, which was awarded plain. Potent ial damage from the ponding of because of depressed economic conditions then storm runoff is currently negligible; existing in Ogden, were that the construction however, future pressure can be expected for of projects funded by the grant be 1) initi­ development of the weeded area. ated within 90 days and 2) completed within one year. Since many unimplemented plans for The flood hazard along 2nd Street in the storm draina?e were "on the shelf" in the vicinity of Washington Boulevard is aggra­ City Engineer s Office, compliance with these vated by inadequate drainage facil it ies for provisions was feasible. Of the total amount storm runoff. A shopping center, supermarket, awarded, $4.1 million was allocated to storm and several shops are located adjacent to the drainage, 'and this was sufficient to imple­ intersection. On the south side of 2nd Street ment every plan the city had ready. between Washington Boulevard and the railroad approximately a mile to the west, there are The project, to construct a new drainage sevei!al low pr iced homes and a few business system for the entire downtown business buildings fronting on the street. A low area district and provide a variety of significant along the east side of the railroad tracks improvements at other locations, was started north of 2nd Street is pastureland. Damage in December 1977 and completed on schedule potent ial appears s light because the flood one year later. Centralized detention basins hazard is concentrated in the pastureland. were utilized to the greatest extent practi­ The recently iristalled storm drain on Wash­ cal. However, in the downtown area there was ington Boulevard will alleviate the hazard, no ava ilable s pace for detent ion bas ins and the city is currently expanding the so it was necessary to construct larger storm drainage system to contain the 10-year event. drains. An evaluation to determine what would happen during the 100-year event would be worth­ Scattered areas in the north part of the while. The flood hqzard identified by FIA city and about 100 acres in the south end are along Washington Boulevard itself is largely developing rapidly. There is also continuing to indicate that flood waters will flow down pressure for urban development and recre­ the street, and it does not riecessarily indi­ ational use further up the mountainside above cate much potent.ial damage to the numerous town. stores and other businesses located along both sides of the street. Ogden officials were briefed on the FIA program in April 1978. Preliminary flood At the fourth location inspected, Ogden hazard maps prepared by FIA are obsolete River flows in a deep channel through Ogden because of the extensive improvements to the business and residential districts. The storm drainage system in 1978. A detailed bridge at Washington Boulevard appears to be

72 adequa~e to handle flood flows. Pineview and risk in areas below irrigation canals may in Causey Reservoirs, Bureau of Reclamation many cases significantly exceed the criterion projects located on the mainstem of the Ogden of one event in 100 years used to define RIver and South Fork Ogden River, respective­ floodplains. ly, provide considerable flood protection from rain and snowmelt floods or inating A second plausible preventive measure above the reservoIrs. Approximately 23 would be tighter controls on recreat ion square miles of drainage tributary to the vehicles and other uses that devegetate or river is uncontrolled. The Corps estimates a otherwise rut and erode mountain slopes. 100-year flood on the Ogden River in downtown Since the uses that caused the problem Ogden to be 1690 cfs (Corps of Engineers are already illegal, this approach requires 1971) • All in all, the flood risk a long the greater effort in patrol and enforcement. Ogden River appears to be fairly low. Discovered rutted or eroded areas could be treated by erosion control measures similar In contrast, along the base of the to those used when slopes are laid bare by mountains, on August 18, 1979, 7 Ogden homes construction activity. The CCC and other suffered extensive damage and about 23 agencies were very active in doing this sort more suffered lesser damage. A total loss of work in the 1930s, but high labor costs amounting to about $1,000,000 was triggered have almost eliminated such efforts in recent when a cloudburst washed mud and debris down decades. The alternatives for cost effective the mountainside. According to an analysis by erosion control using modern technology the Utah Geological and Mineral Survey, the deserve further explorat ion. Even with use mountain slopes had been extensively used by control and land treatment, however, one off-road vehicles to the point that much of can still expect rare natural events to the protective vegetative cover had been worn erode enough soil to fill an irrigation ditch away. The rainstorm then washed sediment and below. Furthermore, a regulatory and land debris down the hill to fill an irrigation treatment approach may require state assis­ canal at about 2:00 a.m. on a Saturday tance for coordination among town governments morning. The canal consequently overtopped, and between towns and the counties having the irrigation water flowed down the steep jurisdiction over the unincorporated areas slope below the canal eroding a great deal of above them. soil, and this eroded sediment caused the principal damage to the homes below (Salt A third approach would be through flood Lake Tribune, August 21, 1979). The area fighting. In the 1979 Ogden flood, the inundated was not in a mapped floodplain, ef forts of a group of members diverted the and none of the residents had purchased flood flow of mud and debris away from a church insurance. building that accordingly escaped essentially undamaged. The short warning times make this Damagewise, this was a major flood for approach very difficult at the base of the Utah. Only one other flood in the history of steep slope, but the flow moves more slowly the state has caused greater economic loss. on the flatter land to allow time for some Some doubt exists as to whether the losses protective effort. Building locations and would have been covered had these homeowners ~esigns are thus particularly critical,at ~he had flood insurance because most of the flood ImmedIate base of the slope; flood f 19hung water was from an irrigation ditch even becomes more practical at greater distances. though the event was triggered by rainfall. The episode shows the need for residents Parowan living at the base of mountain slopes to purchase insurance, and Utah should do its Th is I ron County communi ty is a member best to make sure that coverage for this sort of the emergency program with a populat ion of problem is available through the National between 1000 and 5000. The city lies on the Flood Insurance Program. distinct alluvial fan northwest of where Parowan Creek discharges from the mouth of Insurance, howeveI'., does not prevent Parowan Canyon. The chief channel flows damage from occurring. Several preventative westward from the mouth of the canyon along measures are plausible. One would be to the base of the Hurricane Cliffs. A second convey irrigation water on steep hillsides channel carries water diagonally through above highly damageable property in pipes the town from southeast to northwest, and an rather than ditches. This is done at some unused irrigation ditch runs northward locations where water and debris flow down from the mouth of the canyon along the east natural depressions, but in this case the edge of town. The latter two channels ruts from the recreation vehicles caused the present the worst flood problems as they f low to come down the mounta ins ide at a collect flood waters and carry them into location where it wouldn't normally be town. expected. Certainly standards for construc­ t ion (or structural improvement) of irriga­ There is no stream gage on Parowan tion facilities. on hillsides above urban Creek. The USGS topographic map shows areas and of new urban development immediate­ a drainage area of 68 square miles above the ly below hillside ditches deserve review, and mouth of "the canyon. Based on Equat ion 2, a the state may have an important role formu­ 100-year flow should be no larger than 3440 lating criteria for that review, just as it cfs. Flooding could be caused by cloudburst does now in reviews for dam safety. The or snowmelt, but the former is the more

73 lIkely. Woolley (1946) records floods coming is increasing in this area subject to sha.11ow down the canyon and washing debris into town flooding. In 1857, 1874, and 1906. Butler and Marsell (1972) record eight flash floods near Parowan A third flood hazard zone begins at the over the 30 years covered in their report. diversion point mentioned and runs diagonally On August 1, 1955, flows from Parowan Canyon through the city. A number of homes are in damaged roads, homes, and gardens. On August this zone. City officials feel flooding is 2,1963, the creek overflowed its banks to very unlikely in the area because during high wash thick red silt over several hundred flows the diversion gate is closed to force acres of farm land and to a depth of nearly water down the main channel. If the diversion 10 inches around one farm home. About $600 gate were left open or overtopped, basement in damage, including $100 to buildings, was flooding would occur along the diagonal zone. reported after a cloudburst caused a flow of 500 cfs from Parowan Creek. The last flooding Enforcing the requirements of the flood in the city occurred in 1976 when cloudburst­ insurance program does not appear to have washed debris clogged the culvert under the created problems for the city. They have canyon highway, caus ing shallow flow along successfully kept new development out of the the eastern edge of town but little damage. more hazardous areas. A problem may exist, One can summarize this hazard situation by however, in that the communi ty does not noting that major damages have not occurred consider the entire area subject to flooding to buildings and most losses have been in the by the 100-year event as hazardous. agricultural areas beyond the city limits. One of the main differences between the No flood control structures have been Parowan flood hazard and that at the Cache built on Parowan Creek. A gravel pit Valley towns of Millville and Hyde Park is at the mouth of the canyon provides an that the community is located immediately incidental holding basin but little protec­ below the mouth of the canyon before the tion against the larger flood flows. emerging flow has opportunity to disperse or percolate underground. This factor together with the larger drainage area tributary to Parowan has exper ienced an annual the canyon and the greater hazard of intense populat ion growth of almost 5 percent in rainfall as one moves southward in the state, recent years, partially due to its convenient make Parowan's risk somewhat greater than location with respect to winter and summer that in the other two communities. The Cache recreation areas. Portions of the floodplain Valley communities have the alternative of have been and are being developed. intercepting the flood water, but a struc­ tural flood control program for Parowan needs FIA first issued flood hazard maps for to explore what can be done to make sure that PaJowan in August 1974 showing the entire the gutters and streets disperse and harm­ city in a floodplain. An appeal of the lessly convey away rare flood flows. boundaries led to a revised map in December 1975, with a reduction in the designated Pleasant Grove hazard area from the whole town to the three strips described below. Parowan entered the This city is a Utah County member of the emergency program in June 1975. No detailed emergency program having a population study has been announced. in the 5,000 to 50,000 range. Pleasant Grove lies on the alluvial fans formed by Grove The des ignated hazard areas cons ist of Creek and Battle Creek. The mouths of both three narrow strips. These run along the canyons are on the eastern border of the south (Highway 9) and east (3rd East) edges city. Neither stream has a well defined of town and on a diagonal southeast to channel below the mouth of its canyon. Under northwest from 3rd South 1st West to 4th normal conditions, both empty into the Provo North 6th West. The south strip follows the Reservoir Canal which runs parallel to the creek channel from a gravel pit at the mouth mountains about a half mile below the canyon of the canyon to the west edge of town. mouths. The older parts of town are below Several homes are exposed to flood damage in the canal, but much new development is this zone between 1st East and 2nd West on occurring above it. 3rd South. A diversion structure at 2nd West channels low flows into the diagonal The city has been growing in recent hazard zone, where the water is used for years at an annual rate of almost 7 pe'rcent. watering lawns and gardens. Downstream from Bench lands between the town and the canyon the diversion, the main stream channel is mouths are pr ime development areas with new used only to carry excess runoff. Little subdivisions on both. The pressure to development is present along the main stream develop was probably increased by the con­ channel below the diversion point, and struction of detention basins at the mouth of proposals for development are discouraged by both ,canyons, although bench land real estate the city. in general in the Utah Valley has experienced high growth pressure. The east hazard zone follows the course of a now unused ditch. A few homes lie There are records of localized flooding within this area, and several new ones are to in Pleasant Grove. Butler and Marsell (1972) be constructed. Thus, the damage potent ial record cloudburst floods creating local

74 dralnage problems on June 9,1958, and fans, depositing considerable debris. On the floodIng from Battle Creek on August 19, lowlands to the west of the city, periodic 1959. In February 1979, rain on frozen rises in the level of Utah Lake inundate ground caused some basement flooding. In the nearby property. Third, snowmelt, heavy 1960s, a debris basin was constructed at the rains, or both in combination can increase mouth of each canyon, and land treatment flows in the Provo River to the point of has been applied to the watersheds as part of inundating nearby lands and damaging property the Soil Conservation Service's American along its route across the city to Utah Lake. Fork-Dry Creek Watershed Project. Both debris basins are designed to reduce the The population of Provo has been growing 100-year flood flows (655 cfs on Grove Creek at a rate of about 1 percent annually since and 411 cfs on Battle Creek) to 32 cfs. 1970, somewhat less rapidly than in the According t~ a recent report, however, previous decade. Considerable population and residual flooding at that frequency is still economic pressure to develop floodplain lands possible because of poorly maintained has led to occupancy of a substantial portion channels below the detention basins (Utah of the alluvial fans and the floodplain a County Council of Governments 1974). A the Provo River. Development on the bench problem could also occur should the basins be likely to continue as long as suitable allowed to accumulate debris. undeveloped terrain is available. Residential development is also occurr ing along Utah FIA notified Pleasant Grove of an Lake. unmapped flood hazard in 1975. The city judged its regulations to be in conformance FIA deslgnated flood hazard areas in with FIA requirements and decided that Provo in February 1974, and revised their map joining the insurance program would not in 1976, reducing the designated flood prone impose any new requirements on the city and area somewhat. Provo entered the emergency its residents. Thus, the city joined the program in January 1975. FIA contracted with program in August 1975, but contested the the Bureau of Reclamation in August 1976 to mapped flood prone areas on the basis that complete a flood insurance study to define the flood hazard should be reevaluated now the hazard area more carefully. The resulting that the detention basins are installed. FIS entered its review period in August 1978. FIA subsequently withdrew the flood prone After a three month extension, granted to des ignat ion, and Pleasant Grove elected enable the resolut ion of some disagreements to remain in the program. A detailed study over the contents of the required floodplain, begun in December 1978 is not yet completed. management ordinance, Provo' entered the regular program in February 1979. The floodplain management program in Pleasant Grove includes ordinances in According to the flood insurance study, conf ormance wi th the emergency phase of the the three canyons, Little Rock, Rock, an~ federal insurance program. Specific enforce­ Slate, drain watersheds of approximately 0.8, ment has included prohibiting fill or con­ 9.4, and 6.0 square miles, respectively. The struction from infringing on the Grove and Provo River has a drainage area of 680 square Battle Creek channels and requiring new miles, of which 107 are below Deer Creek subdivisions to be designed so that peak Reservoir. The estimated 10, 50, and 100- runoff will not be increased. In contrast to year flood flows are listed in Table 13. The the smaller communities, the local officials amounts for the three smaller basins are seem to have formulated their floodplain considerably more than ever recorded from any management program independently of FlA. watershed in Utah of similar area (Figure 8). The major doubt as to the adequacy of Incidental snowmelt flood protection the Pleasant Grove program relates to un­ provided by Deer Creek Reservoir, approxi­ certainties as to whether the debris basins, mately 12 miles upstream from the mouth of as constructed and maintained, can contain Provo Canyon. If funding is provided for the the 100-year flood. When they are overtopped, Jordanelle Reservoir through the Bureau of whether by that event o'r a larger one, the Reclamation's Central Utah Project, further city should provide a floodway for the snowmelt protection on the Provo River will resulting flows to pass downstream. The be provided. River flows can be somewhat state may need to take a role in establishing reduced by diversions into the Timpanogos standards and checking debris basin and and Murdock Diversion Canals at the mouth of downstream conveyance des ign to prevent Provo Canyon. A discontinuous system of unacceptable safety problems. levees contains flood flows from the Provo River over most of the reach within the Provo Provo City boundar ies. Localized flood ing may occur through gaps in the levees, and as the Provo, a city of over 50,000, entered river nears Utah Lake. Provo Ci ty and Utah the regular program in February 1979. County share responsibility for annually The city is subject to flooding from three clearing the river channel of debris. sources. On the bench areas on the eastern The most recent flooding from the Provo River s ide of the city, flood waters periodically occurred in 1957, and the largest flood of discharge from the mouths of Slate Canyon, record was in May 1952, when the flow rate Rock Canyon, and Little Rock Canyon and reached 2,520 cfs (a 50-year event) and spread out over their respective alluvial caused cons iderable damage. Butler and

75 Table 14. Summary of flood flows in Provo. slopes and impermeable soils make the peak ---. flows from the canyons on Provo's east boundary higher than in similar c;!nyons elsewhere in the region. However, the U.S. Drainage Peak Discharges Flooding Source (Cubic Feet Per Forest Service has applied land treatment to Area and Location Second) a 11 three watersheds, and all three have (Square detention basins at the canyon mouths. None Miles) 10- 50- 100- of the basins provide prote~tion against the Eq. 2 year year year 50-year even t.

Provo River, 1 mile 680 1800 2600 3200 5770 . Land use in the 0.5 square mile flood below canyon mouth zone below Slate Canyon is primarily resi':' Rock Canyon Creek, at 9.4 865 1710 2100 2200 dential, except for a few acres of orchard, mouth of canyon the Utah State Hospital on the north, and a Slate Canyon Creek, at 0.8 305 526 637 1260 gravel pit on the south. Residential develop­ mouth of canyon ment has generally proceeded up the alluvial Little Rock Canyon fan. Homes in the lower reach are generally Creek, at mouth of 6.0 538 1120 1600 1990 older, smaller, and of frame construction; canyon and homes in the higher areas are larger, newer, and of brick. Source: Provo FIS. Land use in the 0.75-square mile flood zones of Rock Creek and Little Rock Creek is residential. Homes are fairly large and new. Marsell (1972) record eight cloudburst The price of lots average over $20,000, and storms. Most caused local storm draihag~ it is unlikely that any of the homes would problems and none resulted in flooding in the sell for less than $75,000. Under the city by river. or canyon flows. Earlier, a ordinance enacted pursuant to the regular cloudburst on August 31, 1913, c~used flood­ phase of the flood insurance program, homes ing from Rock Canyon that filled streets with in the flood zone begun after February 1, mud and debris and flooded homes (Woolley 1979, must elevate the lowest floor to the 1946) • altitude of the crown of the nearest street, a requirement that precludes most basements. Land use in the mapped 100-year flood­ This requirement has created some financial plain of the Provo River is largely recre­ hardships and has generated considerable ational (a golf course) on the north, resi­ controversy, not only in Provo but in other dential in the middle reach, and residential, areas of shallow flooding such as Springville commercial, and agricultural near the lake. and Payson. The controversy has apparently The worse problems have occurred in the Provo been sufficient to persuade FIA officials to River Canyon above town. On July 13, 1938, a change the AD designation bo a B zone below mudslide, 400-feet wide and 20-feet deep, Rock and Little Rock Canyons. dammed the river inundating resorts and summer homes (Woolley 1946). One may suspect that the quickly passing flood flows in these areas could be deflected High levels in Utah Lake are caused by away from buildings and passed downstream high volumes of total spring runoff. Basement in gutters or ditches in a manner that would flooding is caused by temporary rises in the not threaten basements. On the other relatively shallow water table near the lake. hand, basements filled with water and debris The flood insurance study calculated the conSltitute the preponderance of the histori­ surface elevation of the 100-year flood to be cal flood damages to structures on alluvial 4494.5 feet above sea level, about 4.5 feet fans in Utah and continuing to build them above the normal elevation. invites continuing trouble. The main nonagricultural land uses in Richlhond the 4-square mile lake flood zone are the Provo Municipal Airport and the Utah Lake Richmond is a Cache Valley member of the State Park. The airport is bordered by a emergency program in the 1000 to 5000 popu­ system of levees, but it does not provide lation range. The town is built on the north protect ion from the 100-year flood. Several side of an alluvial fan below where City homes and commercial structures are located Creek enters the east side of the valley. in the mapped flood hazard area. Most of the Cherry Creek, about 2 miles further north, new development on Provo's west and south eros ses an undeveloped corner of the town. sides have been located outside of areas Two southward flowing itr igat ion canals are subject to lake flooding. On the south. the shown on the topographic map to end at flood zone joins the natural marshland of and thus presumably discharge unused water Provo Bay. into City Creek upstream from town. In con­ trast to the typical alluvial fan situation Flooding along the small mountain front where the creek soon dissipates into a canyons is caused by summer cloudbursts and very small and perhaps undefined channel and characterized by rapid concentration, high perhaps because of the irr igat ion water velocity, and high sediment loads, but with discharged into it, City Creek passes through short durations and shallow depths. Steep Richmond in a large deeply eroded channeL

76 Cheriy Cre~k is also deeply incised. The Army Corps of EngIneers as part of the larger only record of flooding that could be found set of floodplain informat ion stud ies wh ich was a cloudburst that washed out roads and cover the Jordan River drainage between the Inundated farmland on July 24, 1923 (Woolley Jordan Narrows on the south and Cadahy Lane 1946). No. record was found of flood ing in on the north (1969 and 1974). These studies lown, and no flooding is mentioned by Butler delineate the floodplains of the natural and Marsell (1972). stream channels, but do not identify the area of flood hazard from canals. FIA designated Field observation of City Creek revealed the flood hazard areas in Sandy in July 1974 that there are about a dozen homes in the as those described by the Corps of Engineers. $50,000 class along the creek within city A rev ised map, issued in January 1976, adds limits and in the area designated on the FIA areas along the canals and reduces the size maps as having a flood hazard. The creek bed of the designated floodplains along natural was overgrown with brush and appeared to have drainage ways. This sort of revision makes a other debr is and obstruct ions that \\'ould great deal of sense, not only for Sandy, but contribute to flooding in the event of high also for the many other Utah communit ies runoff. wherein irrigation ditches can be blocked by sediment or filled to overflowing by water When the FIA program was presented to during cloudbursts. the city, the administration talked to numerous "old t imers" about any history of After these changes, Sandy joined the floods and found no record of any flooding. emergency program in February 1975. A de­ The city decided to go along with the FIA taied study is underway, part of a group of program since it was offered by the federal studies covering Salt Lake County, but government although they could uncover no findings are not yet available. Accurate potentional problems. Since enrolling in the mapping of the floodplain in this sort of flood insurance program, the city has made s ituat ion involving ungaged mountain water­ people that build in the mapped floodplain sheds, dispersed flow over valley areas, and aware of the availability of flood insurance, interception of flows by ditches only to have but none have purchased any insurance. No them break out at some other locat ion is an mandatory floodplain management practices extremely difficult assignment. Since have influenced building decisions. In the city is in an area of rapid urbanization, December 1979, FIA shifted Richmond to the a great deal can be done in the design of regular program through the special conver­ streets and gutters and urban development sion provisions. patterns to minimize the problem. Flooding along the natural streams and i rr igat ion canals has occurred in the Sandy Sandy is a member of the emergency vicinity, but records and accounts of damage program In the 5000 to 50,000 populat ion have not been kept. For example, Butler and range located on the east side of the Jordan Marsell (1972) do not mention a single flash Valley in a rapidly developing area south of flood in the area. This should not be taken Salt Lake City. The commun i ty has been to mean that there were none but rather that annexing a great deal of territory in recent the community has not been recognized as a years, and the city limits are very irregular separate entity long enough to recei~e as they bypass unincorporated territory to recognition in the press for nearby flooding. include more distant subdivisions. Perhaps more impor tant, gr owth has changed both the soc io-demogr aph ic character of the The main natural drainages are the community and many aspects of the phys ical Jordan River flowing north on the west hazard. Both changes increase the probability side of the city and Dry Creek flowing of flooding catching the population unaware. westward on the south s ide. Several smaller canyons emerge from the mountains to the Sandy has grown at a rate between 3 and west. Willow Creek passes through the 4 percent for the past several years. The southeast corner near Willow Creek Drive. In irregular city boundaries are evidence of addi t ion, the area is crossed by several substantial growth through annexation. In canals and ditches which may overtop tneir general, land use passes from commerc ial banks as a result of runoff collected from and older residential, to newer residential, summer thunderstorms. The Galena, Jordan to agricultural or idle as one travels and Salt Lake, East Jordan, and Sandy Irr from the city's center in any direction t ion Canals run from south to north through except north. Development in flood hazard the west half of the city. Sandy Ditch and areas has been occurring at a steady, though Dry Creek flow generally east to west through not rapid, rate for some time. The flood the city. Flooding along the Jordan River zones along the Jordan River, Dry Creek, and is caused by rapid snowmelt, occasionally East Jordan Canal were selected as represen­ augmented by general rain, in the watershed tative of Sandy's flood hazard and. examined tributary to Utah Lake. For the other in more detail. watercourses, flooding is caused by intense summer thunderstorms. The Jordan River follows the city's west boundary from 98th South to about 92nd South, A 100-year floodplain was mapped for with an average floodplain width of 500 feet. Sandy by the Sacramento District of the U.S. Much of this area would be inundated by the

77 proposed Lampton Reservoir, an element of the the southwest. One irrigation canal flows -" Bureau of Reclamation's Central Utah Project, for about a block through the southern end of Bonneville Unit, and will not be developed town but is not a possible source of flooding for this reason. The city has, in addition, for the town above. The three cloudburst reserved for open space the land immediately floods mentioned by Butler and Marsell (1972) below the proposed dam. One request for for the town occurred in canyons some dis:" development has already been denied. Further tance to the east. The flood of July 25, development in the Sandy segment of the 1911, on the Spanish Fork River crested after Jordan River floodplain is thus being pre­ a 4-foot rise (Woolley 1946) and was thus vented. nowhere near entering town. Dry Creek has a drainage area of 14 The FIA identified the Spanish Fork square miles,S of which are below the River as a source of flood hazard in 1974. canyon mouth, and empties into the Jordan City. officials appealed the designation, River near 94th South. Most of the stream arguing ·that the area within the city limits below the canyon mouth is within Sandy. The was well above any flood hazard from the Corps of Engineers (1974) has calculated that river. The appeal was sustained, and .FIA the 100-year flood flow would reach 1,200 cfs withdrew its flood hazard designation. at the canyon mouth and diminish to 600 ds Occas ional backup of local runof f in the by the confluence with the Jordan River. urban storm drainage system was the only Flows approaching this magnitude have not flood problem identified, and it was not been observed, and even the Corps estimates considered to be serious. are considerably less than the 2180 cfs indicated for 9 square miles by Equation 2. The city is in as flood free a location Five bridges (those at the Glena Canal, State as one could expect to find. One could note Street, 10200 South Street, 700 East Street, that the FIA program put the community to a and 1300 East Street) part icularly obstruct needless eKpense in designating a flood haz­ flow, increase the damage potential to the ard that had to be removed by appeal, but canal and roads, and broaden the upstream such hassle was not unreasonable for a flood area slightly. No buildings were national program floundering in its early observed in the floodplain. A detention stages. dam at about 300 East significantly reduces lesser flood flows but would pass flows Wales greater than downstream channel capacity during the more eKtreme floods. All in all, Th is Sanpete County town of under 1000 Dry Creek does not seem to pose a serious was selected as one considered by FIA to have flood hazard. a flood problem but where no hazard area had been mapped. The site for the town of about The East Jordan Canal enters the city 100 people is located at the foot of an li~its at 10600 South and about 200 East, alluvial fan at the mouth of Wales Canyon to flOwing in a generally northerly direction, the west. and exits at about 8400 South and 300 East. Little hazard from the canal edsts through The base flow emerging from the canyon the. southern half of th is stretch. To the has its source in spr ings about 2 miles up north, the canal passes through the center of the canyon. The springs sometimes go dry in the city. Although development has generally late summer but generally flow enough to been kept back from the channel, a few homes maintain the stream. Heavy rains or rapid are eKposed to basement flooding. snowmelt in the mounta in watershed have caus,ed the flooding of cropland south of The City of Sandy regulated development town. The only event recorded by Butler and 1n flood prone areas pr ior to entering the Marsell (1972) occurred July 31, 1965, federal insurance program. Regulation in the and caused $10,000 in damage to Wales Canyon recently annexed areas was previously pro­ road and lesser damage to the culinary vided by Salt Lake County's floodplain water system and to agriculture. Woolley management program. To this time, membership (1946) noted four floods in August 1909 as in the insurance program does not appear caus ing cons iderable damage but did not to have caused significant enforcement costs specify the type. No damage to dwellings has for the city nor caused developers to go to been documented. Some washing from a gravel much expense in changing locations or methods pit at the mouth of the canyon has spread of development. gravel onto marginal foothill cropland west of Wales. Spanish Fork Residents of Wales and the surrounding This Utah County town was selected as a area do not appear to be concerned about city in the 5,000 to 50,000 population range whatever potential flood hazard exists, and not ment ioned in the FlA list of Utah com­ the community has made no effort to partici­ munities by· program status and thus for which pate in the Nat ional Flood Insurance Program. no floodplain has been identified. The town This seems to be another case of a small town is located on the slope of East Bench several that may, but there is some doubt, suffer mi les west of the base of the mountains and significant damage during a 100-year flood about half a mile away from and about 10 to and where the danger during even rarer events 15 feet higher than the Spanish Fork Rive~ to is from shallow dispersed flooding.

78 Washington Terrace West Point citizens eligible to buy insurance later should cont inued upstream development Th is community just south of Ogden was aggravate their problem. se1~cted as a city in the 5,000 to 50,000 popui'ation range cons idered to have a flood Summary of Survey Findings pr oblembut where no hazard area has been mapped. The town lies on high ground sepa­ The descriptive information obtained in rated f tom the Wasatch Front by Burch Creek surveying the floodplains in the 32 sampled which intercepts any flow coming down the communities were not verified or analyzed in canyons. The only possible sources of detail. That was not the intent. The goal flooding are storm runoff originating was rather to get an overview of primary and within the town and whatever flooding Burch secondary problem situations, and that was Creek may cause to low lying property in its what was accomplished. Because the survey deeply incised canyon. The latter possibility focused on an overview of ways the statewide is ruled out by the flood insurance study program might be strengthened rather than prepared for that creek by the Sacramento recommending specific actions to correct the District, U.S. Army Corps of Engineers, flood problems of specific communities, none November 1970, where the lowest corner of the of the 32 community problem descr ipt ions in town is shown to be some 50 feet above this chapter should be considered as a standard project flood stage. thorough analysis of that community's prob­ lem. Each should instead be read as what The town has constructed detention a review of that community's situation basins and storm drains to protect new contributes to identification of needs to subdivisions. The city has declined entry in revise and strengthen the state and national the National Flood Insurance Program because programs. For example, many times a problem its off iei'als felt that they did not have a already encountered in one community was not river ine flood ing problem. The evidence redescribed when encountered in a second substantiates this judgment, but some resi­ community. The findings are presented in two dents may benefit from C zone rates to insure parts. The first relates to problem dif­ themselves against damage from local storm ferences among the 23 categories in the runoff . stratified sample (Table 12). The second is a listing of principal identified problems. Differences Among Community Types This low density subdivision in Davis County was selected as a town in the 1000 to Since all Utah areas as big as a county 5000 populat ion range considered to have a recognize some flood prone locations, all flood problem but where no hazard has been the Utah counties sampled were making mapped. The town is located on land gently efforts to join the flood insurance program. slop toward the Great Salt Lake some miles The rural counties tend to have only scatter­ below base of the Wasatch Front and away ed farmhouses outside their incorporated from any natural water course. The only areas, and these are largely on high ground. conceivable source of flooding from flows New development largely occurs within the originating outside the community would be town. Accordingly, rural counties ~an for communit ies above to discharge storm provide an opportunity for their citiz.ns to water runoff where it would flow down the buy some security against the uncertainty slope into West Point. Such a problem would of unexpected flooding for very minimal be best handled through county or state nonstructural program act ivity. The rural efforts to coordinate the drainage programs counties thus consider membership as worth of the individual communities as urban their while, but it does little to solve development in the area cont inues its rapid their real flood problem of damages to roads, pace. ut ilit ies, and agr icultural. That problem can only be expected to grow worse as federal Th is study found ,that under current agencies become less active in structural conditions Bountiful has a flood problem and flood control. Only in a few Utah cases, West Point has none because of its distance however, is that problem sufficiently severe from the base of the Wasatch Front. Continued for the benefits to correct it to justify ur banizat ion may reverse the sit uat ion and the cost. the policy followed by the National Flood Insurance Program can do nothing to help The urban count ies are experiencing West Point prevent, development of a future rapid population growth that is changing problem because flood hazards for that lowland storm runoff hydrology, expanding the program are defined on the basis of existing popUlation and increasing building density on condi t ions. floodplain areas subject to shallow flooding, and causing more people to move closer West Point has constructed a storm water to the base of the mountains where mud slides storage and drainage system to protect new occur. These count ies are moving ahead with subdivisions. The absence of a natural flood ent ry into the Nat iona1 Flood Insurance hazard is a plausibly sound reason to decline Program and implementation of the non­ entry into the National Flood Insurance structural regulations it requires. The Program. A counter argument would be that greatest problems these communities face are complying with the program now would make the needs for more effect ive methods for

79 dealing with floods and mud flows immedi.ately 2. Th~ larger Utah commUnities, which below the base of the mountains and for are installing storm drainage systems and bet ter coord inat ion among the act ivi ties of basing their designs on containing the the various cities and towns and for the IO-year flood, are not analyzing the effects construction of drains that serve several of their installations on the IOO-year or and none can af ford a lone. These count ies larger floods, both inside their jurisdiction would be especially well served by technical and for those downstream. Future flood improvements in flood hazard mapping on al­ events where serious downstream damages will luvial fans and in flood proofing techniques be caused by upstream storm drainage facili­ against water and mud flows. ties are inevitable. The incorporated cities and towns which were not entering the National Flood In­ 3. Des igned and d.e facto (beh ind surance Program were found to have no river­ culverts, in irrigation ditches, etc.) ine flood problem. Many, however, have some storm ~ondage and debris basins are being problem with occasional flows from hollows increasingly used despite the fact that they and c.anyons from adjacent mountains ides, but are maintenance intensive and improper opera­ they were not entering because of an impres­ tion and maintenance can lead to failures sion that this situation could not be covered with serious downstream consequences. These by insurance. Better communications are valuable structures need to be examined for needed to resolve th is misunderstanding, and performance should they be improper ly ma in­ many of the communities in this group could tained or experience larger than design serve their citizens better by acting to events. Pondage which induces seepage should make it possible for them to obtain insurance be evaluated to determine where the water against this sort of event. goes. Downstream floodways should be pro- , vided. The communities entering the program were divided between those which recognize a primary flood problem and saw flood insurance 4. Upstream urbanization, recreation as one way to deal with it and those which developments, and recreation vehicle use are did not think they had a problem but decided causing runoff, sediment, and debris problems to enter. because it was easy to do and could for those below. Land treatment is part icu­ potentially help some of their citizens. larly important as a flood damage reduct ion measure in arid climates where so much of the Many of these reduced th~ir floodplain management requirements and insurance cost to damage is caused by the sed iment content of residents by successfully appealing overly the flood water, and yet the technology for conse'rvat ive mapping. cost effect ive land treatment does not seem to be being significantly advanced and finan­ None of the communities have become cial programs are lacking to help communities active enough in nonstructural flood control protect watersheds above completely urban ef forts to have encountered s ignif icant areas . costs. Nor have their programs been strong enough to have created incidents of de'­ 5. The hazards delineated in the velopers feeling that they were seriously various communities are not being defined handicapped by program requirements. Recent­ on an equal basis. Some, for example, have ly, however, such smaller communities as flood areas defined along irrigation canals Helper and Castle Dale are beginning to send wliile others do not. Some have been able to signals that the cost of satisfying the remove flood hazard deSignations through the regular program requirements may be more than app,als process for areas of no less risk they want to pay. Others may be following than are still mapped as flood prone in other suit, and FEMA should consider the appropri­ communities. ateness of modifying its required regulations for situations where they must be inforced in small towns to protect against infrequent, 6. Generally speaking, floodplain shallow flooding. mapping in Utah is too conservative in delineating areas at hazard from larger Principal Identified Problems drainages and overlooks hazards from local flooding. The history of flood damage in the 1. Utah communit ies do not have an state shows the latter situation to be a effect ive technology nor an effective major damage soutce. coordinative structure for dealing with flooding at the mouth of small mountain 7. Many areas in the state have either canyons and which may be aggravated by never or not for many years exper ienced mingling with irrigation water. They a major flood. For small, arid basins, no do not have effective methods for problem runoff at all may occur ,for decades. The q uant if icat ion, and they are not formulat ing effects of a single large event on uns.uspect­ effect ive controls. The problem is compounded ing residents can then be devastating. It is since areas with this hazard are not recog­ ibuch more difficult for the people in this nized by most flood insurance studies, and sort of community to understand their hazard people relying on these studies for guidance than it is for the inhabitants of more humid to avoid flood risk are mislead to believe clim~tes where smaller floods are more that the problem does not exist. visible.

80 CHAPTER VI ANALYSIS OF FLOOD PROBLEMS

Introduction implemented. In this case the program needs to be augment ed . The survey of 32 communities accumulated general descriptive information on Utah flood 3. Nonequal marginal rates of sub­ hazards, primary problems caused by the stitution: The community may be relying hazards, structural and nonstructural efforts on one measure when in fact some other to mi t igate them, and secondary problems measure might do the job more effectively or associated with the efforts. From the at less cost. Over emphas is on either the results as described in Chapter V, one has to structural or nonstructural approach at the conclude that 1) flooding causing about $4 expense of the other is an example. In million dollars in damage annually and about th is case, shifts are needed from the over­ one drowning every three years is a signifi­ emphasized to the underemphasized program cant problem for Utah and 2) the ef forts to components. deal with the problem are often poorly directed or at least inefficient. In order 4. Nonequal marginal rates of trans­ to move from this negative conclusion toward formation: The community may be adequately constructive recommendations, the next dealing (or even devoting marginal costs in step was to explore problems revealed in the excess of marginal benefits) with some flood survey in greater depth. problems while neglecting others. Such would be the case if a community had an effect ive program to deal with riverine flooding Classification of Flood Program but was ignoring problems caused by hillside Problem Types runoff. Some conceptual order was given to the diversity of problems encountered by clas­ Selection of Communities s Hying them by a taxonomy based on the for Analysis theory of economic optimality. Flood control requires multiple measures to achieve mul­ Review of the information reported in tiple goals, and four situations can keep a the last chapter led to select ion of seven multiple-input, multiple-output process communities as having significant flood from being nonoptimal (James and Lee 1971, p. program problems of sorts that cover the 61-90). Specifically: classifications in the above taxonomy and that need to be understood better to improve 1. Marginal costs in excess of marginal the effectiveness of Utah's flood control benefits: A community may have (either as a efforts statewide. Generally, rural areas site in which a federal program is being were not found to have much problem. The implemented or through its own efforts) a greater difficulties were encountered along flood control or floodplain management the rapidly growing Wasatch Front where program more extensive and expensive than newcomers are more apt to expose themselves justified by its flood problem. Such a to risk or cause hydrologic change that case might, for example, occur if a community increases risk for others. were following federal guidelines in imple­ ment ing a regulatory program too elaborate The seven communities were not limited for the local s ituat ion as evidenced by the to those surveyed in the last chapter costs of enforcement to the local government because discussions with various public and of conforming to the public. In this officials during the survey suggested case, the program needs to be curtailed. some other situations as even more infor­ mative to analyze. The analyses of the 2. Marginal benefits in excess of selected communities were not to encompass marginal cost: A community may not be their total flood problem but only those making sufficient effort in its flood control aspects that would add to better understand­ program as evidenced by the existence of un­ ing the statewide situation. The seven implemented economically justified alter­ communities selected were 1) Bountiful natives. Such a case might occur if a (including the relationship of its problem to community, because of the long per iod that that in adjacent West Bountiful), 2) Brigham has elapsed since it last experienced flood­ City, 3) Helper, 4) Moab, 5) Ogden, 6) Provo, ing, does not recognize the extent of the and 7) Willard. All are located on Figure 10 hazard or if institutional barriers have and are discussed below in alphabetical prevented preferred alternat ives from being order.

81 Bountiful larger "we just have to take our knocks," but the problem this storm drainage policy Three creeks, Stone, Barton, and Mill poses for dealing with the hazard from the (Figure 12), carry runoff from the Wasatch lOO--year event is that hydraulic analyses Front to the east through Bountiful toward have not been performed to estimate those t he Great Salt Lake to the west. Under knocks. Consequently, the flood insurance natural conditions in this arid climate, not program does not have the information needed very much runoff entered these creeks as they to establish actuarial rates for providing passed through the present townsite. Urban­ flood insurance coverage. More important, ization, however, increased runoff and caused the measures that prevent flooding during the local drainage problems because of the lO-year event may aggravate the hazard during. lack of natural channels to convey storm the lOO-year event. water to the nearest creek. It is nbt easy to obtain these needed Over the past 10 years, Bountiful has estimates. The problems of estimating urban been correcting this problem by constructing runoff and natural stream hydrographs and collector sewers to convey storm runoff to combining them are complicated. The single the three creeks. Small (1 to 6 acre) factor doing the most to complicate risk detention basins are designed into the system assessment, however, is the sedimentation to hold back the flood hydrograph to reduce problem. Basins are filled and sewers size requirements for the storm sewers. are clogged by sand and debris washed from Altogether, 25 to 30 projects costing over $2 the mountain sides or open land within million have been constructed. the urban area. Material washed into the system can reduce the capaci~y for subsequent Because the financial cost of providing storms. Material carried tinto the system greater protect ion was considered excessive, at the start of a larger storm can clog the the facilities have been designed for a facilities for runoff to follow. Urban lO-year return period. City policy according drainageways, with more crossings and covered to the city engineer is that for anything sections, are much more susceptible to clog-

N

1600 NORTH ST. 1 I : WEST I BOUNTIFUL

"­. I t; '-1-.\...~ _ \0 I. ~ .

Figure 12. Map of Bountiful and West Bountiful. ging than are natural channels. Keep ing the Bountiful individually and by inter­ storm drains cleaned is a major ma intenance acting with its downstream neighbors has gone problem. a long way toward correcting common storm drainage and flooding problems. Others remain The deposition of silt in the streambeds unsolved or are being made worse: also causes a continuing problem as the silt deposited in the streambeds by mountain 1. Sed iment depos its in manmade and runoff causes the water to overflow the banks natural drainageways and sediment laden and flood ad jacent propertl' Those flooded flood water are increasing flood damages. feel that it is the city s responsibility The three principal alternatives for dealing to keep the streambeds clean, however, the with this problem are a) regular maintenance city doesn't always agree. Its response to keep basins and channels clean, b) system depends on whether encroachment by those design incorporating constrictions to ac­ harmed into the floodway contr ibuted to the celerate flow and move the sediment down­ problem. In 1977 the city wrote to several stream and debris basins at locations just citizens experiencing flooding caused by above where flattening gradients or widening clogged streambeds advising them that the channels would cause depos it ion (concen­ city did not feel responsibility for their trating deposition makes removal less expen­ damage because they had encroached on sive and the filling of a debris basin is the streambed by building walls, planting less damaging than the blocking of a bridge trees, etc. In other circumstances, the city opening), c) land treatment tb reduce erosion rechanneled Mill Creek and built a retaining from primary sediment source areas. All wall to correct a flooding problem due to three have their place. For an existing silt deposition after repeated complaints by system, one can reduce maintenance cost and some of the residents along the creek who damage during overflows by land treatment. were experiencing recurring flooding. When system improvement is an option, the des ign should seek an opt imal balance among In spite of the effort spent on its construction cost, reducing maintenance storm drainage system, cloudburst events fill costs, and damages. The maintenance program basements near ly every summer. The city should be based on the contribution of the recognizes that the problem cannot be entire­ cleaning effort to damage reduction. ly corrected with storm drains designed to handle the IO-year event and, consequent­ 2. Community flood control efforts and ly, complements its storm drains with the decisions by individuals in the private nonstructural approach of requiring new sector for dealing with their problem are development to provide grading for drainage handicapped by the lack of information on the on a slope from the buifdings back to the hazard. The technical difficulties· in street and streets designed to carry the providing this information stem from the : flow. An ordinance requires developers to hydrologic uncertainties in estimating flows have their designs inspected and approved from small ungaged watersheds and how the before construction begins. flows are affected by land treatment and sedimentation, the stochastic variability Although this storm drainage program has of storms occurring during various states of done much to alleviate Bount iful s problem, tributary watershed conditions, antecedent problems as well as water have been conveyed moisture, and antecedent system situation downstream to West Bount Hul. In 1971 West with respect to opportunity to clean out Bountiful sued in district court to stop its sediment and debris from the last storm. All uphill neighbor from building collector lines of these difficulties are increasingly severe to discharge urban runoff into the natural as one draws nearer to the base of the creek channels. The judge ruled against West mountains and as more human act ivity (con­ Bountiful with a decision that as long as the struction, recreation, etc.) occurs on small drainage comes from within the basin it watersheds draining into urban areas below. co u 1 d bed is c h a r g e din tot h est ream s . Methods for def ining the extent of these Nevertheless, BountifuJ cooperated with floodplains and the degree of hazard within West Bountiful, Centerville, and Davis County them are essential to an informed public and in a project rerouting Stone Creek from the pr ivate flood damage mit igat ion efforts and west boundary of Bountiful to the lake the establishment of actuarial insurance (Figure 12). In 1979 West Bountiful joi'ned rates. A major discrepancy between the with the County and Phillips Petroleum degree of hazard and the insurance rates, one Company in installing a 6-foot diameter drain way or the other, is going to cause long line to carry excess flows in Mill Creek run problems for the insurance concept. This through the city to its west boundary. point, however, does not preclude the wisdom Finally, the city has plans fot diverting of in some cases USing single low rates over Barton Creek flood f lows to Stone Creek large areas because the. benefits of being (which has excess capacity) on the east side more precise are just not worth the trouble. of the city, but difficult financing and right-of-way problems· must be solved before 3. Local storm drainage system designs the plans can be implemented. The city based on controlling the lO-year event need doesn't have enough money to do the project to be better coordinated with the national on its own; and according to city officials, program to ~inimize damages caused by the county funds are not readily available IOO-year event. Bountiful and West Bountiful either. are cooperating to keep uphill storm drainage

83 systems from increasing downstJeam dam9ges shOwn on Figure 13), 25 acres would b~ during the 10-year storm, but: neither com­ s I: t ealnway, and 100 acres would be Open munity is reckoning with what the system will or ag;J:'icultural land (mostly downstream from do during the 100-year storm. The grading f;o the area shown in Figure 13). keep water out of basements and from ponding in yards and the facilities to speed drainage It is anticipated that flooding would out of Bount iful are doubt le!>s going to deposil: silt, sand, and Jocks on streets, reduce (alpeit not to zero) damages duri!:!g lawns, gardens, and pastlJre. Res ident ial the 100 as well as during the design 10-year losses would incllJde dplllage to foimdaqons, event. D9wnstream in West Bounf;iful, how.,­ basements, heating systems, floors, furnish­ ever, it is doubtful that the incl'eased ings, and lawns and gardens. Commercial channel si2;!9S will be sufficient to handl.a losses would include damage to structures and t he amount by wh ieh f lows are increalOed eq u i pment, loss of bus iness and i nV.entor ies, d uri ng the s e 1 a l' gee ve n t 10 • An a 1 y sis is and cOsts of clean ~p and repair. AgrielJI­ needed for floodptain mapping inthes~ tural 19sses would include erosion, deposi­ downstream areas and for more equitabll'l tion of silt and l1eigis, damage to farm resolution of !:he total problem. improvelIlents, and cost!'! of !:l).elln up. 4. The total flood hazard also qepend$ Examination of the flood hazard area on land use and facilities construction between 300 North and 600 NQrth and between within the unincorporated Ilreas uphill from 100 EaSI: and 400 Ellst discovered approxi­ Bount iful. Downstream des igns need to be ma.tely 50 homes located i9 an area where the coordinated with upstream watershed condi­ principal damage would be basement flooding t ions. Land use planning for, the hlture by sheet flow. West of 100 East tqe flood­ needs to be cooqlinated with budgeting for plain is very narrow, and only hOlIles located future storm runoff faeHities. Allocation!'! next t9 the creek would be affect ed. Eas t for equitable distribut ion of required costs of 406 East, ihe creek ~oes th~ough a park in among communH;ies need to l?e cOnsuD1lI!atel1 in a fairly well-defined channel. Some homes binding cost sharing agreelIlents covering located on the creek east of the park are maintenance as well as construction. subject to minor flooqing. Brigham City The flood hazard is aggravated by varipup obstru~tions~o the ~h~nnel flow. Whjle Brigham City is potentially Na~ural obstructions include trees, brush, threatened by flooding hom both Box Elder and other vegetation growing in and along the Creek and smaller hollows at the base of the streamways. Manmade obst]:uc~ions include Wellsv;illeMountains, only the foriner problem virtua.lly all the bridges and culverts in the is ,discussed here. That emphasis, however, city (Table 14). . shouJd not be tak.an as dismissing pof;enti.:il problems iH the mouth of the lOmall canYons, Ci!=y offieip).s eXpresse!:! the opinion even tholJgh n9 record was found of damage that the Corps of Engineers' analysis of the from that sourCe. It is only that fol' ftopd hazard in Brigh~ Ci~y exaggerated the the purposes of this study, flooding from flood threa.t, Accor!:!ing t9 the officials runoff from mountain hollows is covered 1>Y interviewed, the city has not passed any the other exalIlples. ordina.nces reptricting development on the floodplain, but the building inspector did Box Elder Creek has flooded Brigham City indicate that it has been a. customary prac­ periodically since settlement in the mid tice to require new houses to be constructed 1800s. The most st;!riqus flooding occurred in witb~the first floQr a.bove the 100-year flood February 1911 when snowmelt, possibly aug­ lev~l. mented by heavy rain, resulted in record runoff. Obstructive bridges diverted water Despite the negativeness of these into the city, bridges were washed away, and expressions, the city is participating in the a sect ion of railroad track was washed out. FIAins4rance progtam, and several people There is no recent history of s!,lchsetious liVing in the f).oodplain have purchased flood flooding. inslJr~nce. It was 'the opinion of the Public Works Director that this insurance had been The area ident if ied as having a flood plfrlZhased prim,u ily to satisfy restrict ions hazard (zone A) on the FIS Flood Hazard imposed on lending institutions by the flood Boundary Map (June 12, 1979) follows BOJ!: insurance progra.m. Elder Creek (Figure 13). Tn is area is com,. pletely developed except for a few scatter~d The CQunl:y Office of Emergency Services vacant lots. The Corps of Engineers' st;udy feels that there is a significant floqd of flood hazard in Brigham City (Corps of h~zard in ~righa.m City from Box Elder Creek. Engineers 1975) shows roughlY the $.~~@ In 1978 it condl-lt::\:e·cI a. fl~!;h flood exercise floodplain, blJt the mapping dis!:inglJish~s th~ wHhif\ !;:h~ ?lrea ma.PPed as, Petl1g supject ~o flooding problem along' the creek; from that; inundation by thelOO-year fl~qd in which back from the creek and associated with sheet 300-400 peqp).e Were evacuated from !=heir flow. According to the Corps' study, a total homes. of 170 acres would be inundated in 8r igham City by a 100-year flood. Of the tot

84 "- \ \ \ \ \ \ 100 51 \ \ .... ;' \ \ ,.. _ \ \ I \ \1 \ \ .... , A I\ \ ,,- 300 ST. " " BASIN \ " .... ,\ \

... 500 51 ..... - ......

Figure 13. Brigham City flood hazard area.

85 Table 14. Obstructive bridges and culverts.

Top of Identification Under- Road- Location Stream- clearance way 100-yr b bed c c Flood

Interstate Highway 15d 0.82 4217 4220 4230 4221 1800 West Street 6.37 4228 4231 4232 4232 Union Pacific RR 10.73 4276 4278 4282 4280 5th West Street 12.38 4304 4308 4310 4307 3rd West Street 13.27 4320 4324 4326 4326 2nd West Street 13.62 4327 4332 4333 4332 1st West & 5th North Streets 14.15 4337 4341 4343 4341 Main Street 14.72 4348 4355 4356 4352 1st East Street 15.23 4358 4363 4364 . 4362 4th North Street 15.44 4365 4369 4371 4370 2nd East Street 15.73 4369 4376 4378 4375 3rd East & 3rd North Streets 16.44 4388 4391 4393 4393 4th East Street 17.17 4400 4405 4407 4406 1st North Street 18.34 4430 4436 4439 4436 6th East Street 18.61 4434 4440 4442 4440 Forest Streetd 19.37 4454 4459 4468 4466

aAII elevations are rounded to the nearest foot, mean sea level datum. bDistance in thousands of feet upstream from Black Slough. CAverage elevation. dCulvert. Source: Corps of Engineers, Sacramento District, Floodplain Information, Box Elder Creek. Brigham City, Utah, June 1975, p. 16. 41 p.

the canyon and 400 cfs at Main Street in with in it, in these c i rcums tances would Brigham City. Box Elder Creek drains an area provide a much sounder basis for floodplain of 33 square miles of which 15 square miles management. More important, it would define drain into Mantua Reservoir. Excluding the parameters which flood control and floodplain controlled area, Equat ion 2 gives that management efforts should be addressing to be the I8-square mi Ie drainage could produce a effective. One important application would be flood flow of up to 2550 cfs at the canyon in the design of measures that work to mouth. The maximum recorded peak flow convert the flooded area from a random to a in Brigham City is 159 cfs, recorded on constant pattern. February I, 1911. The period of record was 1909-1912, but local sources say that a . 2. Most of the bridges crossing Box flood of that magn itude has not occurred Elder Creek cannot pass the 100-year flow since. w i thou t s i g n i f i c an t b a c k wate r, and the smallest bridges determine the points where The above informat ion suggests that the the banks are overtopped. Vegetation growing primary flooding problem along Box Elder within the channel reduces its capacity Creek has several distinctive characteristics further, becomes a source of debris that relative to hydrologic analysis, damalie clogs bridge openings, and adds tandomness to estimation, and measure design for Utah s the flooding patterns by causing bridges that flood problems: would otherwise have no problem to be the ones that back water onto adjoining property 1. The presence of a defined channel during a particular storm. Cleaning vegeta­ that has remained at a fixed location for at tion from the channel would thus have the least 100 years makes the type of flood risk benefit of improving flood pattern con­ analysis proposed by Dawdy (197.9) inappro­ s iatency, but the benef it should be we ighed pr iate for Br igham City. Nevertheless, the against cost, environmental effects, and flows that overtop the channel banks are downstream effects. The vegetation contri­ unconfined and spread at fairly shallow butes to the natural process of spreading depths over a large area. Delineation of the flood flows at the canyon mouth so that the hazard area is handicapped by difficulty in flooding problem does not extend very far estimating what volume of water will escape, downstream. The net effects of enlarging which way it will flow, and how far the flow bridge openings depend on the balance between will go before it will be rendered harmless the damage caused in the 10cat ions where through containment in gutters and di tches. water spreads after being diverted at the The development of methods for delineat iog bridge and the damage caused if the water is t he hazard area, and def ining the hazard instead spread by another smaller bridge

86 downstream. One can visualize sIzIng bridge general concern for the smaller cities and openings to spread the water where property towns in Utah entering the regular phase of will be damaged least. Certainly, the series the federal insurance program is the cost and of bridges must be viewed as a system, and personnel necessary to comply with the the enlargement of individual bridges should inspect ion requirements for new development not be undertaken in disregard for downstream and substantial improvements to older build­ effects. ings. The work, as described in Chapter III, includes such efforts as checking buildings 3. The flood hydrology prepared for Box for compliance with respect to lowest floor elevations and the use of flood resistant Elder Creek shows 100-year peak flow esti­ mates of 1100 to 1600 cfs at the canyon mouth materials. Cities with significant flood to decrease to about one third of this amount prone areas and part time building inspectors 1.5 miles downstream at Main Street. A worry that the required ordinance may impose an unwelcome and perhaps financially unten­ detailed hydraulic analysis could determine how much of this decrease is caused by able extra burden on inspectors. They also percolat ion to groundwater; how much by worry that the requirements will impose an detention storage in the stream channel, unfairly large cost burden on land develop­ mentact ivities and cause their community to settling basin, and adjacent lowlands; and how much by water being diverted from the lose out in kinds of economic growth that stream into overland sheet flow through town. they consider important. As the side in such Since the entire floodplain area mapped as cont rovers ies hav ing much greater resources, subject to sheet-flow flooding is upstream it would behoove FIA to either develop facts from Main Street, one would expect this last and figures that can be presented to al­ cause to be considerable. From the results, leviate these fears or to relax requirements one could obtain some valuable insights on where the facts and figures cannot justify a the hydraulics of flood hydrograph dissipa­ larger program. tion after emerging from mountain canyons and on designs that would be effective in dis­ sipating the flooding for much less cost than An additional problem has surfaced as that of a large channel to convey the peak some question the legal status of the through town. The potential for cost reduc­ flood hazard zones designated by FlA. Utah tion can particularly be seen in the fact law requires that zoning changes be made only that a structural solution of bridge enlarge­ after public hearing. Since data limitations ments and channel cleaning for Box Elder and hydrologic uncertainties make precise Creek through Brigham City would require a delineation of the 100-year floodplain 1600-cfs channel all the way to Black Slough. impossible, legal boundaries are based on rough information. As better information becomes available or physical conditions Helper change (through upstream urbanization for example), more accurate or new boundaries can Analysis of the Helper situation concen­ be delineated. Perhaps the requirement for trated on program administrative costs and on a public hearing can be satisfied by presen­ difficulties associated with significant tation and discussion of the technical growth restraints or location shifts that facts. The legal status of the revised maps, would result from the more comprehens ive should the reaction of the public at the floodplain management effort required hearing be unfavorable, is unresolved. of communit ies enter ing into the regular phase of the flood insurance program. Helper only has a po~ulation of 2200, but it At this time, a revised ordinance is located in an area where coming fossil submitted to FIA by Helper appears to fuel development is expected to trigger major be acceptable to both for resolving the economic and population growth. immediate situation. If approved,Helper would automatically be reinstated into the While a city map .hows large tract of insurance program. undeveloped land (Figure 14), much of this open space is rough terrain relatively unattract ive for development. The except ion Whether or not this case is successfully is the open space along the Price River at resolved, the' compat ib i li tyof FEMA flood­ the south end of the city. At the time the plain management requirements with the study began, a subdivision had been proposed techni~al and financial capacity and with the on the tract. Plans have since been with­ long run economic goals of small towns is drawn, though apparently not because of going to continue to be an issue. Perhaps floodplain regulations. requirements should. be relaxed for small towns where the benef its from a more demand­ ing floodplain management program would be The connection with this situation is meager, and the state should take a leader­ uncertain, but Helper is showing increasing ship role in promoting this change. Perhaps, reluctance to continue with a floodplain the communities should have technical and management program of the sort expected by financial help in meeting the requirements, FEMA. Helper was suspended from the insurance and the state should provide supporting program when FIA rejected its flood control services needed to make this possible. The ordinance on nine counts. The issue of more appropriate course is now unclear.

87 HELPER FLOOD HAZARD AREAS

TO I PRICE Figure 14. Helper flood hazard area.

Moab plat~~us of the north and south mesas and then to almost vertical sandstone canyons Moab was selected as a town with a below the mesa area. Infiltration is almost substantial flood problem for which a number zero on the "slick rock" cliffs of these of structural and nonstructural solutions had canyons but is moderately good on the al­ been proposed but where-very little has been luvium of the mesa. Both snowmelt and cloud­ done. The town lies in a valley (Spanish burst flooding occur with the cloudburst Valley) approximately 12 miles long and 1 flood being the more severe and less predict­ mile wide. The valley is bounded on the east able. and west by sandstone cliffs locally called "slick rock." The Colorado River flows from the east, goes around a bend 2 miles north of There are written records of flooding in Moab, and then flows to the southwest. Mill and near Moab as early as 1881 (Woolley and Pack Creeks, which originate in the La 1946). Severe damage to dwellings, busi­ Sal Mountains to the southeast of Moab, flow nesses, roads, bridges, and farmland has been parallel to each other into the center of the documented over the years. According to city and converge. Then Mi 11 Creek flows U.S. Geological Survey records, five :cloud­ into the Colorado River approximately 1 mile bU1st floods were recorded during 1881-1900, west of town (Figure 15). 23 during 1901-1920, 31 during. 1921-1940, 23 during 1941-1960, and 19 durmg 1961-1969, The Mill Creek watershed has diverse for a total of 101 for the period 1881-1969. characteristics. Slopes vary from moderate Since that time, floods occurred in 1970, in the La Sal Mountains to flat in the 1974, 1976, and 1978.

88 The Soil Conservation Service (1975) Flooding in Moab is not solely caused by completed a flood hazard analysis for the two streams running through town. Bliss Moab and the surround ing area as a step in and Tusher Canyons drain "slick rock" areas planning for structural flood control. Their east of the city and discharge onto developed estimates for instantaneous peak discharges areas below. The result ing damage was suf on Mill Creek and Pack Creek for various ficient to qualify the problem for remedial frequencies are given in Table 15. The Corps action under the CCC program during the of Engineers estimate a standard project 1930s. Debris basins were constructed in flood peak in excess of 23,000 cfs. The Bliss Canyon and at the mouth of Tusher maximum probable flood peak has been esti­ Canyon. mated to exceed 74,000 cfs (Utah Division of Water Resources 1976). Moab is thus obviously in much more hazardous posit ion than is Brigham City where the 100-year flood at Main Table 15. Estimates of the instantaneous peak Street was estimated at only 400 cfs. discharge for Mill and Pack Creeks near Moab, Utah. The Soil Conservation Service (1975) reports that flooding from Mill and Park Creeks increased with agricultural develop­ Flood Mill Pack ment of the upper watershed. A report in the Frequency Creek Creek local newspaper, The Times Independent, dated (year) (ds) (cfs) August 23, 1901, suggested that the Pack Creek channel had increased from a 16-foot to 100 14,000 10,400 a 100-foot width in 5 years. Interviews with 10 3,800 2,800 two engineers in Moab also suggested that 2 800 500 the flooding became more frequent with increased use of the upper watershed. Source: U.S. Soil Conservation Service (1975).

LEGEND

=@= U.S. HIGHWAYS " ~ =€)= STATE HIGHWAYS --- CITY BOUNDARY ...... -- RIVER a STREAMS ~ 100 YEAR FLDOO AREA ~ 100 YEAR FLDOD AREA (ALWVIAL ~N I

Figure 15. Mo~b flood hazard area.

89 Structural efforts to control flood ing The preliminary FIS has been completed from Mill and Pack Creeks were begun by the (Federal Insurance Administration 1979). The Civilian Conservation Corps (CCC) in 1936. 100-year floodplain as delinepted in Figure Mapping of the potential dam sites on Mill 15 can be seen to cover much of the central Creek was initiated by the Utah State Engi­ city as well as residential subdivisions to neer in 1938. The Bureau of Reclamation the east and southeast. Most of the benefits (1959) listed a small structure on Mill Creek from flood control are in the areas outlined in its Pack Creek Project Report. The in Figure 15 although some occur in Spanish reservoir would have been sized at approxi­ Valley to the south. mately 2,500 acre feet to be used primarily for irrigation but with some storage reserved Considerable flooding has occurred in for flood protection. The Corps of Engineers' downtown Moab between first and second study of the area in 1963 recommended chan­ South on Main Street with the most recent neling Mill Creek through Moab. In 1969, the event in the Spring of 1979. Figure 16 Bureau of Reclamation recommended an arch illustrates damage in the area just east of dam on Mill Creek to serve for flood protec­ the Main Street Bridge. Other illustrations t ion, irrigation, and recreational use at a are found in Soil Conservation Service (1975) cost of approximately $10 million. The Utah and Corps of Engineers (1979) reports. Division of Water Resources was asked to join with the Corps of Engineers in a joint effort to determine the needs of the Moab area in Despite this history of efforts to 1970 and recommended an earth and rock fill analyze, report, and recommend remedial dam on Mill Creek. The U.S. Soil Conservation structures, floods still cause considerable Service completed a report in 1975 on the damage. Wi th the except ion of the catch flood hazard in response to a request of the basins constructed in Bliss and Tusher Moab City Council for a more detailed Canyons, the studies have produced only analysis of the flood problems on Mill and recommendat ions. Local of bcials ind icated Pack Creeks. The last three reports have their frustrat ions in not gett ing projects been issued by the Utah Division of Water financed and underway. They were also Resources (1976, 1977) and the Army Corps of concerned as to how to restrain growth on the Engineers (1979). The benefit-cost ratio upper Mill Creek watershed that is increasing es timated for the most favored project was runoff through town. 1. 29. It is interesting to point out that although city officials have urged floodplain residents to obtain insurance coverage on all buildings and mobile homes and their con­ tents, the response has been scattered, even in the face of continued flooding and delay in constructing flood control structures. Only 81 policies for a population of 4500 are shown in Table 10. Residents in Walker subdivision, businessmen in central city locations, and residents in the southeast areas of the city were interviewed briefly to determine their attitudes and concerns about the flooding problem and the damages they have exper ienced dur ing recent floods. All those interviewed were located within the 100-year flood zone. None could assess the probability of damage nor its extent for their particular area of the city. Some had flood insurance, but more did not. Those who had experienced damage could estimate losses in terms of replacement costs for carpets, pipes, lawn, and household art icles, but could not state a subject ive probability of that same damage recurring.

Several of those interviewed were confused about the FIA insurance program, and some had not heard of the program at all. Some knew the program existed but did not know that the City of Moab was a participant. A relatively small number had strong com­ plaints including such specifics as a lack of communication between city officials and the citizens, delays in getting flood protec­ tion, and continual damage to their property. However, none of these complaining residents Figure 16. Flood damage in downtown Moab. and businessmen carried flood insurance.

90 While quantitative delineation of atti­ not have coverage, spent $34,500 for walls tude patterns is unreliable without a more along the bank of the Mill Creek to contain carefully controlled sampling procedure, res­ the flood water. Part of the wall was washed idents and businessmen obviously lack infor­ out in the 1976 flood. Another motel owner mation on the probability and extent of dam­ in the same area has spent $22,000 on walls age (Kunreuther et al. 1978). Residents and rock work since 1972 to direct the Mill and business managers located on the 100-year Creek channel away from the motel. Another floodplain do not perceive the low proba­ business built a 4-foot concrete wall and bility-high loss decision process outlined in gutter to contain and direct the flood the insurance and economic literature (Arrow waters. The approximate cost of the struc­ 1953, Hirshleifer 1970, and Kihlstrom and ture was $9,300. Pauly 1971). They lack the necessary infor­ mation about risk and loss to select the Despite a long history of recurring optimal insurance coverage by weighing the flood damage, recognition at the community expected cost of insurance against the level of a serious problem, and recognition benefits of coverage should a disaster occur. at the national level that structural mea­ They are unclear about the probability of sures are justified, no structural program flooding in their area and the extent of the has been implemented to protect Moab. loss. A primary role of the insurance agent Furthermore, the goals of the National Flood is to provide this information, but the Insurance Program of covering losses to agents are not informed either. The agents existing property through insurance and of obviously need help so that they can do a using the availability of that coverage as an better job of marketing flood insurance. incentive to promote floodplain management prac~ices are not being achieved either. The Property owners may also believe that following factors can be hypothesized forgiveness grants or low interest loans may as contributing to this situation: be forthcoming from the federal government to cover uninsured losses or that flood 1. A belief within the community that damage may open an opportunity to refinance the flooding is caused by upstream land use at a lower interest cost. Such opinions, development and hence they rather than the however, are in conflict with recent legisla­ floodplain occupants should pay for the tion (PL 93-234, PL 93-288, and PL 94-68) losses. that has moved away from such disaster relief programs as forgiveness grants, essent ially 2. A belief within the community that zero interest loans, etc., to more loss structural measures are coming or that other reduction-contingent insurance programs and forms of financial relief will be available higher interest loans. to make insurance on floodplain management less necessary. Some losses were estimated from the interviews. Some $63,000 in clean up 3. A feeling that the floodplain costs, excluding new carpet and furniture mapping overestimates the hazard and thus costs, were estimated at the time of clean up that there is really no need to buy insurance after the June 1962 flood. Some residents in much of the mapped area. A community in who experienced loss from that flood offered this situation often appeals to FEMA to have costs ranging from $1,500 to $8,500 to the designated floodplain area reduced, but a replace household items and clean up the community with good prospects of obtaining debris and silt. During and after the 1974 structural relief could through such action flood (a 10-year event), one motel in the reduce benefit estimates to the point where a downtown area had to evacuate for 2 weeks. project would no longer be feasible. Its 45 units normally bring an average rental of $26/unit/day for a total loss of business 4. Ineffective salesmanship for flood of $16,380. The 1976 flood forced evacuation insurance in the community. of the lower units of another motel in the same area. Its 33 units. for 2 days normally br ing an average rental of $25. 50/unit/day for a $1,683 loss plus s $3,600 clean up This city provides a good example of bill. Neither motel carried insurance. Two innovative designs in an active storm drain­ mobile homes were flooded in the upper Mi 11 age program at the community level. The Creek watershed during the 1974 flood causing increased runoff and result ing storm water uninsured losses of $7,500 and $8,900. problems brought by urban growth gradually In the June 1967 flood, an inventory of became serious enough for the people to $9,000 worth of automobile parts was washed demand action, and city government began to away from a service station supply shed. respond about 1969. In that year the city Repair costs for roads and bridges (the adopted the Weber County master drainage plan latter damages ranging from $40,000 to and prepared to act within the framework $200,000) were much higher. of the proposed county system. However, most of those storm drainage plans had to be Considerable investment has been made in shelved because sufficient funds were not flood proofing in downtown Moab by business appropriated to do the work. firms and motels, some of whom have flood insurance and others of whom do not have The experience of this financial limita­ coverage. A motel owner, who apparently does tion led to a planning philosophy followed by

91 the city during the last decade of building a and periodically cleaning the basin. The system 1) at minimum cost and 2) with maximum debris basin of Figure 17 provides a model of utilization of existing conveyance facili­ one of the most effect ive methods for con­ ties. The high cost of building large­ trolling cloudburst runoff and debr is from diameter storm drains to convey water long mountain canyons. distances was apparent. Detent ion storage provides a way to reduce them and thus One issue deserving further examination becomes a basic component of the city's urban is what happens when a very la rge storm runoff control systems. (See page 72.) occurs. Spec if ically. are there cases when storm drainage f.acilities actually make One of the projects constructed by the flooding worse as debris dams are washed out, city with Us Economic Development Adminis­ sumps recharge aquifers with polluted wat.er, tration grant in 1977 is the debris basin and storms fill basins with sediment and flood drain line on 27th Street (Figure 17). peaks from following storms are higher than Runoff washes large rocks, trees, and other ever before because the compensating damping debris down Taylor Canyon at the head of 27th storage is lost, or grading changes urban Street. To intercept the flows and separate watershed boundaries to concentrate flows the rocks and debris from the water, a debris differently. Since state government has basin was constructed at the mouth of the responsibility for dam safety and pollut ion canyon. This basin is essentially a small control, need for reviews of storm drainage earth-fill dam with an outlet box and pipe system designs to protect the public interest for draining water from the basin. Debris need to be determined. and rocks are caught and held behind the dam, thus preventing this material from being Provo washed into streets and yards. The basin is cleaned and reshaped after each storm and As one of the first Utah cities to join periodically, as required. The estimated the regular flood insurance program, Provo benefits from reducing cleanup costs and has committed itself to a strong nonstruc­ damages to yards and basements on 27th Street tural flood control effort. The question to significantly exceed the cost of constructing be analyzed was thus one of what effect

-1 U U U~ ~IS'::. :::::::1 I I L-I_.....III""""=~II""""==:1 :=:::=::::1 L~]I 11- I ~

....TAYLOR CANYON DRAINAGE I DEBRIS BASIN t' I' II I 1 N

21" Rep -- ...... -

RIP RAP OVERFLDW DEBRIS BASIN

Figure 17. Debris basin on 27th Street, Ogden, Utah.

92 is this membership having on administrative declined to consider removing the restriction cost within city government and on municipal until after the system is actually in place. growth in the context of one of Utah's larger The developer was dissatisfied with the delay cities in a rapidly growing area. The flood and the continuing uncertainty as to FIA's hazard area on the eastern bench was the ultimate decision. Thus, indecision and focus of the examination. inflexibility at the federal level has worked to discourage use of curb and gutter systems The floodplains mapped on the alluvial in urban flood cont rol even though such fans at the mouths of State, Rock, and Little designs could substantially reduce damage. Rock Canyons (F igure 18) are c la ss if ied AO because of their shallow flooding. Flood A third sort of design is to use protec­ depths are estimated to be 1 foot or less t ive barriers to channel flood flows around during the 100-year flood. The risk to homes or to flood proof the port ion of any property on the floodplain is low because the structure below the base flood elevation. flooding is shallow. Furthermore, flood This alternative might be implemented either hazard zone delineation and classification for an entire subdivision, probably during are known to be uncertain because of the the period of init ial development, or by difficulty of predicting the paths floodwater individual home owners. Originally, protec­ takes down the fan. In fact, the uncertainty t ive barr iers and flood proof tng to reduce of the floodplain boundary may be so great basement flooding were allowed under FIA that there is really little difference in regulations as a way to avoid the no-basement -hazard between bench areas within and outside restriction. A fairly recent change has the boundary. This is in fact the assumption foreclosed this option for residential made by Dawdy (1979). structures, although the policy is not yet firm. The technical issue that needs to be The regulation setting development resolved is whether or not the proposed restrictions in AO zones is one of the practices can actually be counted on to most cont rovers ial elements of the flood p~event basement flooding, and this deter­ insurance program in Utah. With certain mInatIon requires analysis of subsurface exceptions, the construction of new buildings conditions on the bench area. with basements is not permitted in AO zones once the community enters the regular insur­ ance program. This provision has been en­ The inflexibility in FIA's regulations forced in Provo since February 1, 1979. The covering AO zones has thus restricted first effect of passing the regulation was to the range of alternative responses to the create a rush t6 obtain building permits and flood hazard in Provo and may well be begin construction on flood prone lots prior directing the community toward nonoptimal to the February deadline. Real estate solutions. Some relief is in sight however, developers who failed to beat the deadline as the FIA is giving consideration to re­ then found that their lots in mapped flood vising some of the AO zones to B zones where zones decreased substantially in value. One the restrictions mentioned above do not real estate developer reported that even with apply. a $5,000 reduction in the pre-February price, lots in the mapped flood zone were not The issue of regulation in AO zones has selling. Part of the difficulty, however, also surfaced in Springville and Payson, must be attributed to high interest rates. both currently suspended from the insurance program, and generated enough concern The shallow flood flows in AO zones that Senator Garn has proposed an amendment often make feasible fairly simple, small to pending legislation that would require a scale flood control structures. In Provo, special study of Utah's AO zones by FlA. three designs are common. Holding basins can Here the State of Utah may find a role in be constructed at the mouths of canyons to pressing for regulations that allow flexi­ contain peak flows, sediment, and debris. As bility so that the most economical combina­ mentioned in Chapter V, structures, similar tion of floodplain management alternatives to that shown on Figure 17, have been bu ilt can be implemented. The basic problem is that at the mouth of each of the three canyons. national standards may not be optimal or even These basins would have to be approximately reasonable for the uncertain shallow-flooding doubled in size to accommodate the 100-year alluvial fan situation and that forcing flood, but there are no plans to do so at similarly if not identically worded ordi­ this time. Future analysis may show that the nances for communities throughout the nation reduction in flood insurance premiums to home is creating uniform national standards. owners in the floodplain resulting from enlarging the basins more than offset the With respect to the effects of the costs. regular program on administrative costs and municipal growth as found from the Provo The design of subdivision curb and data, the 6-month old program is too new gutter systems to carry shallow flood for precise assessment but they are likely to flows is another possibility. One developer be large. So far, the major administrat ive drew plans for such a system and submitted cost has been associated with the paperwork them to FIA, seeking to obtain, an exemption of resolving differences with FlA. The of the restriction against basements. decline in lot price suggests a preference to F IA had the plans for 6 months and then shift development elsewhere, a trend which

93 -" PROVO FLOOD PRONE AREAS

N

SLATE UTAH CANYON LAKE

Figure 18. Map of Provo.

furthers the objectives of floodplain manage­ dralns out in Willard Creek passing just ment and shifts growth to other communities. north of town. An irrigation canal runs Objective analysis of the desirability along a contour on the mountainside a of the shift is handicapped because little short distance above town (Figure 19). information is available on the performance of protective barriers and flood proofing Flooding from the creek caused a great during actual flood events. deal of damage on August 13, 1923 (2 women drowned when their house was demolished) and Willard again on July 31, 1936 (Woolley 1946). Following the 1936 flood, the CCC did a The City of Willard sits at the base of substantial amount of upstream terracing, and the Wasatch Front immediately below a point the Bureau of Reclamation or the CCC built a where Willard Peak rises very steeply to an levee northeast of town between the creek and elevation of 9764 feet above the flat lands the town. Field observat ion of the area adjacent to the Great Salt Lake. The very revealed that although there is considerable steep rise of 5300 feet in less than 3 miles sediment deposition and groWth of underbrush creates an orographic uplift which inten­ back of the levee, a sizable flood flow could s if ies precipi tat ion on the mountains ide be contained • Conf irmation can be found in above town. Some of the runoff runs directly the facts that floodwaters from the creek down tbe face of the mountain largely bare of have not entered town since 1933 and the vegetation at velociies fast enough to wash a flood hazard mapping indicates that the levee great deal of debris onto the valley floor. could contain the 100-year flood. In short, Much more collects in Willard Canyon and except for the area on the creek side of the

94 N

\ IRRIGATION CANAL en t- :E :::i w !i II:: o Q.. II:: o U

Figure 19. Map of Willard.

levee, the town has less than one chance in a the town and the area south to the Weber 100 of being flooded. County line. The first step was to apply to FEMA to study the hazard in the area, Nevertheless, damaging floods occurred principally from three small canyons east of in Willard in both 1978 and 1979. On August town and four larger canyons to the south 13, 1978, a cloudburst on Willard Peak sent (Figure 20). FEMA responded that their flood flows down the face of the mountain backlog of work would delay the study for south of Willard Canyon. Mud, rocks, and two years (Salt Lake Tribune, November 13, debris from the flood filled in the Pine View 1979). The situation relates to an important perimeter canal for a distance of 1 mile, state role in priorizing studies. causing the canal water to overflow the banks a nd add to the flood discharge. Damages Willard is obviously a community with a to three homes whose basements were filled flood problem, and that problem obviously with mud and debris, lawns, orchards, extends beyond the mapped floodplain area. and gardens amounted to about $250,000. A The consequence is rather that a floodplain simi lar event caused a lesser amount of management and insurance program focused damage at another point along the base of the on the mapped hazard area does nothing to mountain in July 1979. correct the problem of runoff bringing debris down the face of the mountain, block ing the In November 1979, the Box Elder County irrigation canal, and causing waters from Commission pledged to assist Willard in both sources to comingle, erode the hillside, organizing a flood drainage district covering and carry mud and debris into town. In fact

95 studies completed for Utah locations have contributed to a better informed public as to flood hazards; but in a number of situations, the informat ion they provide is not suf­ ficient to establish wise floodplain land use. The reasons for the large degree of uncertainty are in large part technical, and hence research to overcome these technical deficiencies would be of great help. A second pervading problem was one of flood control and floodplain management programs directing their efforts toward lesser hazards while ignoring larger ones (a marginal rate of transformation problem). The effort spent on riverine flood hazards was often extensive even though flood damages were minor, but major damages caused by local runoff from small mountain canyons were ignored, except of course by the individuals left to recover from the loss as best they could. This nonequitable division of flood control effort is aggravated by the technical difficulty in defining this sort of hazard and the understandable tendency of the national FIS program to concentrate on the more familiar riverine hazard. Other lesser problems, not necessar ily in order of importance, include: 1. The marginal rate of transformation problems of putting too much effort on controlling flood waters and neglecting Figure 20. Small canyon watersheds above needed preventive (land treatment) efforts to Willard. reduce erosion and sedimentation. 2. Expenditures for flood control exceeding marginal benefits received in cases of an overestimated riverine flood hazard or the existing program may be making matters where small communities with minor flood risk worse by conveying the impression that would be expected to inaugurate a major property outside the mapped floodplain floodplain management effort. A community is safe and that owners do not need to buy floodplain management program has certain flood insurance. fixed costs (for example for floodplain mapping) which far exceed any possible benefit in small communities with minor flood hazards. Streamflow drains excess precipitation toward the sea. Somet imes the runoff rate 3. The marginal rate of substitution exceeds the capacity of the natural drainage problem of federal requirements forcing way and damages property or even takes lives. Utah communities into a floodplain management This physical problem of flooding becomes an program of a type matching national norms economic problem as well when the response to when in fact special designs (for example to flood events misses cost effective opportuni­ deflect and disperse shallow flooding) would ties for reduc ing the damage or cos ts much be more effective for Utah conditions. more than the damages prevented. These departures from economic optimality can, as 4. The externality problem of the flood described at the inning of the chapter, be control or floodplain management efforts of classified into four groups. one community increasing risk in another. The examination of the seven communities The six problems enumerated above relate showed that the greatest problem in Utah does to urban flooding. In reality, the larger not fall in anyone of these categor ies share of the flood damages in Utah are to but in all four. The major Utah problem is roads and highways and to agriculture. The one of inappropriate response caused by agricultural damages are probably not in most uncertainty. Decision makers at all levels cases large enough to just i£y structural (Figure 1) do not know the magnitude of the flood control programs and nonstructural floods to expect, the locations to expect to measures do not apply. On the other hand, flood, the regulations on floodplain use, how opportunities for improvements in road design changes in the upstream watershed will affect standards whose marginal benefits exceed the hazard, etc. The flood information their costs may exist and should be examined.

96 CHAPTER VI I

EVALUATION OF PROGRAMS AND RECOMMENDATIONS

Introduction and the water spreads out over a larger area and infiltrates underground. Where infiltra­ Chapter II presented a framework of the tion is hindered in urban areas, the flow dynamically interactive feedback processes eventually disperses to the point it can be through which people at various levels collected in gutters or ditches. The issue and from various perspectives seek benefits of how far down the alluvial fan to regulate f rom floodplain occupancy, exper ience floodplain use (let alone how to vary the sequences of flood events, and respond by distance with the type of use) has never been modifying their occupancy or by attempting to objectively resolved, and arbitrary decisions mod ify the pat tern of flood ing. Through in bounding the downstream edges of these these processes, society balances benefits "AO" floodplains create major disagreements against risks. Efforts made by government to between communities and the administrators of alter this balance generate additional federal programs. In an arid climate the impacts, some beneficial (increasing benefits alluvial fans are also crossed by numerous or reduc ing risk) and others det r iment al small irrigat ion canals that can intercept (implementation cost or adverse environmental and convey flood waters to other locat ions or social impacts). That chapter ended with where they break and cause damage where generalized presentations of how the balance flooding would otherwise not be a problem. between benefits and risk and government efforts to change this balance might be Flood risk assessment is compounded by weighed from the Utah perspective. the fact that many Utah communities seldom experience flooding and yet could be sub­ Chapter III moved from this general jected to considerable damage should a major framework to empirical data describing flood flood occur. Residents of these areas risk in Utah. Chapter IV outlined efforts subject to a major disaster, should a .. large at the national, local, and individual levels and rare flood occur, have less appreciation to reduce flood risks or enjoy the benef its of the risk than one typically finds in more of floodplain occupancy. Chapter V inven­ humid climates because lesser events are not t oried and Chapter VI probed s ituat ions in occurring periodically as reminders of .poten­ selected Utah communit ies. The purpose in t ial danger. Furthermore, expert hydrolo­ th is chapter is to analyze the informat ion gists are less able to help them with reli­ presented in these chapters through the able information on flood risk because of framework of Chapter II in order to ident ify the statistical difficulties in predicting needs for· program improvement. Some of the the magnitudes of rare flood events from needs can reasonably be met by action at the sparse data. level of state government. Others cannot. The final goal is to make recommendations on The hydraulic assessment to map flood­ what the State of Utah should do. plains and define flood risks are even more limi ted by a lack of pract ical methodology. Evaluation of Adequacy of Flood Mudflows (Woolley 1946, p. 75-84) are a Hazard Information particular problem. These flows are particu­ larly likely from canyons where weather ing Flood risk in Utah was found to be between storms produces large amounts of relatively low compared with the rest of the loose rock, unstable side slopes are likely country, but considerable danger exists from to slide into the drainageway, and the flash flooding caused by cloudburst storms perennial flow is insufficient to keep the t hat cause the water to rise rapidly in channel relatively clean. From a given mounta in canyons and discharge sed iment and canyon, mudflows are more likely to be debris at the points where the canyons associated with larger storms and after emerge onto alluvial fans at the edges of long periods in which loose detritus has desert valleys. Waters rise quickly to accumulated. According to Hooke (1967), a dangerous depths in the canyons, a situation water f low becomes a mud or debr is flow accounting for most flood drownings in Utah, when it passes the point of irrevers ible and the silt and debris which emerge onto the sediment entrainment. Water flows freely heads of the alluvial fans can do consider­ depos it excess sediment load, but a debr is ably more damage than can flooding by water flow cannot selectively deposit sediments. alone. The entire load is deposited simultaneously when enough water has drained out the As the flood travels downhill over the bottom for the flow to become too viscous alluvial fan, the mud and debris settle out, to continue.

97 Mudflows may emerge either into a river show the risk of flooding at various loca­ flowing in a larger canyon or onto an al­ tions over the fan. The mapping should be luvial fan. The former sit uat ion freq uently performed with a secondary goal of searching blocks highways and railroads and may dam for cost effective ways to constrain the the river to back water onto upstream proper­ hazard area. ty and intensify flooding downstream when the temporary blockage gives way. The event of In conclusion, specific needs exist for July 13, 1938 (p. 76) illustrates just one reducing flood impacts through: of many such events that have occurred in Provo Canyon. 1. Identification of areas at mouths of mountain canyons where mudflows or shallow The distance a mudflow will travel water flooding would be severe enough, as down an alluvial fan is determined by how measured by depths and velocities, to cause long before sufficient water drains out to major damage and loss of life. stabilize the flow. The two major parameters seem to be the size of the flow (the amount 2. Identification of flood risk in of water) and the freedom of the water to mountain canyons for use in siting highways, drain. As soon as the flow enters an area campgrounds, and recreat ion areas and in where the canyon opens out to the point where formulating warning and evacuation procedures water can la terally leave the flow, the for use during flash flood events. State drainage begins. water resources planners could work with state park officials in reducing the risk Different flows move onto the fan in of major loss of life from_ flooding in Utah. random directions (Price 1974). Dawdy's (1979) assumpt ion of equal hazard at all 3. Review of plans to construct trans­ points on a given contour crossing the fan portation and irrigation facilities crossing is reasonable for mudflows because the very alluvial fans to make sure that they will not ridges left by one flow deflect the next flow unduly pond nor concentrate flood waters and in a different direction and because the create significant hazards in formerly flood small manmade levees and gutters which free areas. direct water flow into consistent patterns are relatively less effect ive. The greatest 4. Review of plans to construct storm need is for a method to predict how far drainage facilities designed for less than mudflows of various frequencies will travel the 100-year event to make sure that they before stabilizing. The ideal mudflow are not unduly intensifying downstream risk hazard mapping would show the risk of inun­ during major storms nor extending flood dation at various distances below the canyon problems into new areas. mouth. Because mudflows are so much more devastating than shallow water flooding, a Evaluation of Effectiveness of regulatory criterion much more stringent Flood Control Activity than the 100-year may be reasonable. Prohi­ bition of all residential development may be The uncertainty as to flood risk and the in order. duration between flood events work to reduce the effectiveness with which individuals and The above description of mudflow char­ institutions respond to flood problems. The acteristics suggests that one possibly risk from the 100-year flood as seen by the effective structural approach would be to public is severely underest imated by the develop a long basin somewhat wider than the people of a community which has experienced upstream canyon near or just below its mouth. no flooding since the 1890s and seen water The mudflow wold then stabilize in the basin in their wash only during a few rare events. which could then be cleaned and reshaped A public that has not worried about flood before the next event. problems is not going to know much about government programs for dealing with them. Downstream from where the mudflows Communities whose officials remain in their stabilize, the risk is from shallow water jobs for only a few years must regularly have (often with a high sediment content) flood­ federal and state programs reexplained if ing. Since floodplain mapping is primarily they are not to be forgotten. to provide risk information to urban areas and urban areas have fixed locations and In this context of poor information and designs for gutters and ditches, the danger uncertainty, many Utah communities have will not be uniformly distributed along a entered into the federal flood insurance given contour on the alluvial fan but will program as a means of making flood insurance l' ather be concent rated at locat ions deter­ available to interested citizens. It is easy mined by gutter and ditch geometry. Hence to pass the required ordinances without these need to be measured and analyzed to recognizing the potential cost to the com­ determine risk, or even better, they should munity of enforcing them and, more important, be designed to reduce risk. Other important conforming to program requirements after the factors in determining risk are the locations community enters the regular program. of natural channels, the effort made to clean The program has not yet advanced to the point t hes e ch annels between floods, br idge open­ where one can assess the problems that may be ings, and irrigation canals. The ideal caused as federal program requirements shallow water flood hazard mapping would attempt to acheive less than the economically

98 optimal floodplain use from other viewpoints. Dingman and Platt (1977) concluded that (See discussion on differences in acceptable floodplain management practices are bein~ risk on page 11.) unnecessarily delayed by widespread mis understanding as to the degree of preciSion Uncertainties as to the real flood risk hydrologically possible and legally neces­ have aggravated the difficulties for Utah sary in delineating flood hazards. The Utah communities attempting to establish a reason­ experience is that the problem is compounded able floodplain management program and meet when the methods used consistently miss major FEMA requirements. Flood hazard maps have flood problems. Walesh (1979) described one been difficult to read in areas where build­ of four critical negative features of the National Flood Insurance Program as being its i ngs were not shown and stream channels limited scope with respect to using the were often poorly defined. New information costly inventory and analyses being made in or changing conditions have required map defining flood hazards to find ing solut ions changes, and delays often occurred in spread­ to flood problems. The Utah experience shows ing the information. Perhaps more important, that advances in floodplain mapping meth­ op t imal floodplain management pract ices have odology may hold the key to finding solutions not been defined, and probing questions are in that current techniques are not providing raised as to the reasonableness of those information that is really contributing to required. solving problems. Utah flood damage experience also In summary, the situations where the suggests a special need for coordination greatest opportunity exists for situation­ between transportation and water resources improving action include: planning. The debris plugging culverts as alluvial channels aggrade or during sediment­ 1. Programs to a) augment awareness lad~n storm runoff have added greatly to of citizens and public officials of federal inundation problems to say nothing of ex­ programs to help them solve their flood posing highways to a very large share of the problems and of the requirements to qualify total average annual flood damage. Highways for those programs and b) to train community through the canyons are also exposed to the engineers and planners to deal effect ively cloudburst torrents, and travelers may become with their situations. trapped during the storms if there are not periodic points of road access to higher 2. Assistance to communities dealing ground. Such situations deserve careful with federal agencies on flood control, consideration in highway alignment and floodplain management, and transportat"ion culvert and bridge design decisions. programs. Federal officials may not be thinking of Utah situations as they promote In terms of the framework of Figure 1, their programs, and communities may need the two primary impacting actions in recent technical help in explaining local conditions years in Utah have been localized cloudburst and in express ing their percept ions and flood events and the National Flood Insurance desires to federal officials. Program. The localized events have not sent impact waves past the second or third level Impact Evaluati()l1 from a in any of the five d imens ions; and, cons e­ Utah Perspective quently, the actions that are being taken are at the individual and, in the govern­ In considering the above flood and mental d imens ion, at no higher than the response-decision impacts, one sees a county level. For the most part these are number of reasons for flood control and reasonably effective against smaller storms, floodplain management practice in Utah but untried as to performance against major varying from that elsewhere. This variance events. emphasizes the potential importance of a role for state government in reminding federal officials that Utah situations are different The National Flood Insurance Program has and of providing technical help to com,.. caught the attention of most of Utah's 251 munities and individuals who need to deal communities (162 having 92.6 percent of the with their own problems. Specific needs for population), about 10 percent of the flood­ variations from national programs in order to plain occupants, and state government. The better match the Utah perspect ive include: national structural flood control program is becoming increasingly less active. The over­ 1. Most Utah flood problems are not all biggest current problem is that the effectively solved by large scale structural national programs are not making progress in flood control measures but rather by some addressing the types of flood problems Utahns combination of land treatment to control have experienced in the last few years, even sediment and debr is sources and small scale though a structural solution for Moab has storage and channelization systems designed been studied and found feasible since the to disperse flood flows rather than concen­ 1930s and one recent event was the second trate them at downstream discharge points. most damaging flood of record in the state. The Soil Conservation Service program is the The situation is probably adding to a general best focused on these sorts of designs, but disillusion toward federal programs in the that program is not institutionally oriented social and cultural dimensions. toward the primary Utah hazard areas found in

99 the high ly urban ized Wasatch Front com­ among cOmlllunityengineers and planners. The munIties and in isolated mountain recreation state can sponsor workshops as needed areas. and facilitate informat ion exchange on a routine basis. 2. Only a few of Utah I s larger com­ munities have municipal stormwater control 2. Promote dissemination of information programs and these largely protect against on the risk of major flooding in areas where the 10-year event. The programs of the the danger is not recognized by the public. individual communities are not always co­ This sort of effort could do a great deaIto ordinated with one another nor with the prevent a major disaster when' inevitable problems in containing larger floods. For truly large floods occur. example, a stormwater conveyance system that quickly discharges the 10-year flow at the 3. Provide technical support for downstream boundary of a community may community flood control programs. The also greatly speed the flow of the 100-year support could be limited to a role of doing event and cause s ignif lcantly larger down­ no more than r,esponding to queries of a stream flows for that event than occurred technical nature or could be integrated into previously. an act ive program of reviewing and approving community-proposed structural flood control 3. The federal floodplaIn management measures. Flood control dams are already and flood insurance programs of FEMA have not reviewed to make sure that they will function proved adaptable to the Utah variations from safely during flood events, and many channel the more typical national situations. Repre­ or levee failures can btl just as disastrous sentative issues relate to flood hazard as the failure of the small dam. Regular mapping on alluvial fans, land use regulatory review would also prevent flood control practice in areas subject to dispersed measures in upstream cOmlllunities from worsen­ shallow flood ing, and reasonable program ing downstream damages. The pros and cons of expenditure for small rural communities. a review program should be carefully evalu­ ated before deciding to go forward and before 4. Communi ty f loodpla in management selecting the sorts of review to require programs are hampered by having to be imple­ should a program be found desirable. mented ,from poor hazard information in communit ies whose pr iorit ies are quIte dif­ 4. Since effective designs of distri- ferent from flood concerns and by requir mg butary flood control channels on alluvial response from a populat ion wh ich generally fans and of flood proofing for buildings in believes the federal officials to have the path of shallow surface water flooding greatly exaggerated the problem. Many Utah and underground flow through gravel lenses communities have floodplain management are not available, a potential state role ordinances on the books, but none have exists in developing appropriate designs and achieved fully operational programs. standards. COmlllunities cannot effectively do this individually, and the federal government 5. Individual flood control efforts is too or iented toward problems of great:.er have generally been effective in Utah national interest to devote the needed as can be seen from the low rate of damage effort. occurring to private buildings despite the fact that Utah communities are generally 5. As the federal government withdraws located in the most hazardous areas along the more from structural water resources pro­ base of the mountains (Woolley 1946, p. grams, the states are going to come under 57). Much of this success can be attributed increasing pressure to share or perhaps to an urban design with large lot sizes wholly provide financing for structural flood allowing plenty of space between buildings control. Many communities have needs that for dispersed shallow floodwater flow. As they are financially unable to supply alone. population pressures increase urban residen­ Furthermore, remaining federal programs are t ial dens ity, the flood-ing problem will be moving toward requiring state cost sharing. aggravated unless suitable flood proofing Certainly, the state should review both techniques for Utah conditions are devised federal and local flood control projects and employed. from the Utah perspective before state funds are committed. In certain cases, one can Recomlllendations on Potential expect the economically optimal flood control State ActIons program to require land treatment, storage, or channelization outside the area of the Based on the above information and protected community's jurisdiction. In other analysis, the seven areas where Utah state cases, communities can by cooperation ac­ government would be best advised to consider complish mutual flood control object ives at action targeted to improve flood control much less cost than they can by acting practice within the state are: individually. Most of the projects required in either of these cases, however, are 1. Provide a cont inu ing funct lonal small compared to what is viable for a forum for keeping communit ies aware of what federal program involving the large fixed they need to know to meet the requirements of cost of planning as prescribed by the Prin­ the federal flood insurance program and for e iples and Standards of the Water Resources f aci lit at ing the exchange of exper iences Council and the National Environmental

100 Protect ion Act. Utah may be forced to act, hazard areas from mudflows and shallow water perhaps in conjunction with a requirement of flooding on alluvial fans and in other valley community cost sharing or payback according lands below where small drainages emerge from to local benefit, if economical flood control the mountains. Problems include estimating programs are to be established in these how flows disperse, how dispersal affects situations. Some use of state water project downstream flood hazard, how land grading and revolving funds for flood control may be storm drainage practices are counteracting appropriate. dispersal, and what urban design alternatives can improve the Utah situation. 6. Individual communities often do not have sufficient technical expertise or Other needs should be emphasized from political clout to interact in a way that the 42 listed by Howells (1977) in his effectively represents the interests of their nationwide review. These (by his numbers) citizens when dealing with the federal are: government on flood control matters. The state government can establish expertise at a 2. Development of standards of perfor­ position of sufficient political strength to mance through wh ich the effect iveness of become an important advocate. A state flood alternative flood control programs can be problems office may also have a role in assessed. helping the community deal with other state agencies on certain flood related problems. 5. Establishment of reasonable and legally sound standards for accuracy and 7. Certain additional state legislation reliability of flood hazard information. may be helpfuL State legislation to create special flood control districts may be a 10. Exploration of alternative institu­ reasonable alternative for direct state tional arrangements for coordination of local action to solve flood problems crossing flood control and floodplain management community boundaries. State legislation programs. could also clar ify the s ituat ion when FEMA changes flood hazard boundary maps and hence 14. Development of guidelines to assist the area regulated by floodplain zoning local governments establish optimal flood without the public hearings that are now control and floodplain management programs. required. 30. Development of improved methods Research Recommendations for estimating the effects of land grading, retention storage basins, and channel The pr imary need for research is to improvements in urban areas on downstream develop better methods for delineating flooding.

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106