Interdisciplinary Planning of Nonstructural Flood Hazard Mitigation

B. D. Hayes, P.E., A.M.ASCE1

Abstract: An interdisciplinary team consisting of representatives from state government and academia has developed an innovative flood risk management plan that combines a large-scale ‘‘nonstructural’’ hazard mitigation plan with portions of a federally authorized plan previously developed by the U.S. Army Corps of Engineers. Separate elements of the federally authorized plan were considered for inclusion in the alternative plan based on the estimates of each element’s marginal benefit/cost ratio, potential environmental impacts, and level of consistency with current policy. The plan involves retrofitting approximately 1,500 residential and nonresidential structures in the 100-year floodplain and requires development of a structure-by-structure flood proofing benefit/cost analysis computer program. At less than half the cost, the alternative plan achieves flood risk management goals in a significantly more cost-effective manner for an environmentally sensitive area. DOI: 10.1061/͑ASCE͒0733-9496͑2004͒130:1͑15͒ CE Database subject headings: Flood damage; Remedial action; Risk management; U.S. Corps of Engineers.

Introduction Institute ͑UHI͒ at the University of Massachusetts and the five departments of EOEA met weekly during the early development In 1989, the New England Division of the U.S. Army Corps of process. The participants came from the Metropolitan District Engineers completed a flood damage reduction plan for a region Commission ͑MDC͒, which assumed sponsorship for the Corps’ north of Boston, including portions of Saugus, Lynn, Revere, and project in 1987; the Department of Environmental Management Malden. The Corps’ floodgate plan relies heavily on flood control ͑DEM͒, which has primary responsibility for managing flood haz- structures, most notably, a 1,290-ft-long ͑393-m-long͒ floodgate ards in the state; the Department of Environmental Protection across the mouth of the Saugus River as well as 3.5 mi ͑5.6 km͒ ͑DEP͒, which is responsible for administering environmental of new seawalls and dikes ͑USACE 1989͒. Because of policy, regulations; Massachusetts Coastal Zone Management ͑MCZM͒; environmental, and financial issues, the Executive Office of En- and the Department of Fisheries, Wildlife and Environmental Law vironmental Affairs ͑EOEA͒ of Massachusetts decided to explore Enforcement ͑DFWELE͒. The participation of DEP, MCZM, and whether an alternative plan using a wider variety of techniques DFWELE was of key importance because of their roles in the including non-structural approaches, such as elevating or remov- regulatory and permitting process as well as their ability to articu- ing structures in flood-prone areas, could be developed. Develop- late environmental concerns. MCZM is a state policy development of an alternative plan required several innovations in flood ment agency that advises the Secretary of EOEA on coastal policy risk management planning. First, an interdisciplinary approach and long-range planning and has veto power over federal actions was taken that involved the cooperative efforts of individuals in the coastal zone. A representative from the Division of Marine from various state environmental agencies and academia. Second, Fisheries ͑DMF͒, a branch of DFWELE, also participated in the the plan was reviewed by an external academic review commit- development process. tee. Third, less established methods of reducing potential damages Together, the individual representatives of the five departments through ‘‘nonstructural’’ hazard mitigation were used. Finally, of EOEA provided valuable insight into the process. Besides the benefit/cost analysis for the plan as a whole required the devel- expertise each of these representatives brought when completing opment of a computer program to establish flood-proofing recom- the many tasks associated with the project, the group provided mendations on a structure-by-structure basis for a large inventory advice and direction for the developing plan. As a result, current of structures in the floodplain. trends toward fiscal responsibility via cost-sharing agreements The interdisciplinary approach taken in this work involved with municipalities were incorporated into the project. Similarly, government directly in the planning process for an alternative the goal of avoiding variances in the permitting process is incor- plan. A team consisting of individuals from the Urban Harbors porated directly into the development process. In addition, peer review was sought for the plan. The Academic Review Commit- 1PhD, Senior Project Manager, Sadat Associates, Inc., 1545 Lamber- tee provided comments on the plan both during the conceptual ton Road, PO Box 4129, Trenton, NJ 08610. E-mail: [email protected] phase and later. Note. Discussion open until June 1, 2004. Separate discussions must Within the study area are 1,660 acres ͑672 ha͒ of productive be submitted for individual papers. To extend the closing date by one salt marsh that provide diverse habitat critical to migratory water- month, a written request must be filed with the ASCE Managing Editor. ͑ ͒ The manuscript for this paper was submitted for review and possible fowl and marine life Fig. 1 . The commonwealth’s interest in a publication on January 30, 1997; approved on February 24, 2003. This flood hazard mitigation plan that relies more extensively on non- paper is part of the Journal of Water Resources Planning and Manage- structural techniques in this area was largely for concerns regard- ment, Vol. 130, No. 1, January 1, 2004. ©ASCE, ISSN 0733-9496/ ing impacts on the estuary. Nonstructural approaches minimize 2004/1-15–25/$18.00. impacts on environmentally sensitive areas and reduce the likeli-

JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT © ASCE / JANUARY/FEBRUARY 2004 / 15 Fig. 1. Study area hood of further encroachment on areas such as the estuary of the associated with sea level rise has not been consistent nor has a Saugus and Pines Rivers. Potential long-term environmental im- comprehensive national policy been developed ͑Platt et al. 1992͒. pacts on the estuary are difficult to evaluate because of uncertain- Growing trends in coastal flood risk management on national, ties related to the rate of sea level rise and the lengthy 100-year state, and local levels currently favor softer approaches such as life expectancy of the Corps’ floodgate plan. In light of these beach renourishment. The NRC has stated that plans that can be uncertainties, nonstructural techniques and their associated envi- expected to perform well under existing and future uncertain con- ronmental conservativeness are preferable for this exceptional and ditions should be preferred ͑NRC 1987͒. vulnerable ecological resource. The 100-year floodplain in the study area is heavily developed Flood risk management in an urban coastal setting is by nature and includes approximately 2,000 residential structures and 585 a complex, multiobjective problem. Efforts to minimize natural nonresidential structures. The study area experiences frequent hazards to the population and potential damage to property and coastal storms and some flooding almost yearly. The storm of infrastructure are constrained by a variety of factors. Significant record occurred in February of 1978. Corps’ estimates of total engineering resources are required for analysis of the hydrologic direct and indirect damages and costs for all of Lynn and Revere forces that drive the problem and for the design, analysis, and including parts not in the study area were $52,402,500 in 1994 comparison of potential solutions. Management of coastal flood dollars ͑USACE 1979; Hayes 1995͒. Saugus and Malden experi- risks is similar to flood risks in rivers, excepting two major fac- enced relatively little damage because of their lack of exposure to tors. First, coastal wave action adds complexity to the analysis of direct wave and wind effects from the ocean. potential damages. Second, a more complicating factor is the issue of sea level rise. A coastal flood plan must address an increasingly discouraging scenario of increased frequency and se- Previous Efforts by Corps of Engineers verity of flooding in future years because of sea level rise. Unfor- tunately, the actual future rate of relative sea level rise is highly In 1985, the Corps of Engineers was asked to develop a regional uncertain. The historic rate in Massachusetts has been 0.3 m every flood damage reduction plan by officials of the state and the four 100 years; however, estimates of an increase as high as1mbythe communities in the study area ͑USACE 1989͒. Three alternative year 2075 are accepted by many experts ͑USACE 1989͒. Federal plans were formulated. Two of these plans relied heavily on ar- response to the issue of shoreline recession and coastal erosion mament. Option 1 relied on armament of both the seacoast and

16 / JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT © ASCE / JANUARY/FEBRUARY 2004 borders of the estuary. Option 3 relied on armament of only the year during the years leading up to the end of the 35-year life seacoast combined with the construction of a floodgate across the span͒ do not appear to have been reviewed with regard to envi- Saugus River. These two plans ͑Options 1 and 3͒ had comparable ronmental impact nor the ability to receive permits or variances costs and benefits and received extensive analysis. The third al- associated with increased floodgate closure duration and fre- ternative ͑Option 2͒, consisting purely of nonstructural tech- quency. Current water quality and environmental regulations may niques, had an order of magnitude smaller for costs and benefits. be difficult to meet, particularly in light of the Area of Critical This alternative, which addressed only 9% of the total structures Environmental Concern ͑ACEC͒ and the Outstanding Resource in the 100-year floodplain, was not pursued to the level of detail Waters designations of portions of the study area even under the that the structural solutions were pursued, although the plan dem- initial planned operations involving only three predicted closures onstrated a substantially better benefit/cost ratio ͑2.0͒. The Corps, per year. These regulations could possibly, if not likely, become following their principles and guidelines ͑USACE 1983͒, selected more stringent in the future, further complicating the issue. Option 3 as the National Economic Development ͑NED͒ plan for Because the Corps of Engineers has invested significant effort optimization and further development. The NED plan is defined in the development of a comprehensive regional plan, the team as the plan that reasonably maximizes net national economic de- sought to build on the Corps’ previous work as far as possible. In velopment benefits. the alternative plan, the three primary modifications of the Corps’ Benefits predicted by the Corps ͑USACE 1989͒ for their flood- floodgate plan consist of the omission of the proposed floodgate gate plan were calculated assuming a 100-year period in which no structure across the mouth of the Saugus River, the introduction significant changes in the patterns of commercial, industrial, and of nonstructural techniques such as flood proofing and elevation, residential activity would occur. Approximately 65% of total and omission of new armament in Lynn Harbor. The alternative project benefits were based on inundation benefits, i.e., expected plan does include from the federally authorized plan the following annual damages under current conditions that would not be expe- components: a small tide gate at Sales Creek in Revere; a dike rienced due to the floodgate plan. These inundation benefits are along Revere Beach that would also be developed into a park for calculated based on 13 hydrologically separate zones. Roughly additional recreational benefits; coastal protection at Point of 40% of these inundation benefits were associated with commer- Pines in Revere; and the purchase and protection of wetlands. cial and industrial property. The expected annual benefits associ- These modifications are intended to align the Corps’ extensive ated with the protection of the General Electric plant in Lynn efforts with EOEA’s preference for nonstructural techniques and accounted for 15% of the total inundation benefits of the regional are expected to result in a plan that is more equitable with regard plan. to the distribution of costs and benefits, more cost-effective, and The fully funded first-cost estimate for the federally authorized more environmentally sound. plan is $114 million. Approximately 35% of this cost is to be The Corps’ benefit/cost methodology ͑USACE 1983͒ requires provided by the commonwealth, which represents a significant choosing projects with maximum net benefits. Unfortunately, this fiscal burden. Operating and maintenance costs are the sole re- ignores budget constraints often faced by other agencies affected sponsibility of the commonwealth and are dominated by costs by the project. For a government body facing a budget constraint, associated with the floodgate. A review of these cost estimates the relevant criterion is the maximization of the net benefits per ͑Hayes 1995͒ suggested that they could have been underesti- dollar spent on a particular project. Thus it is always worth sub- mated. The possibility of insufficient funding for proper opera- dividing projects as much as possible in order to determine tions and maintenance increases the chances of interruptions and whether certain parts of the project provide greater marginal net brings attention to state and federal concerns regarding induced benefits than other parts. This is particularly relevant in the case development upstream of the floodgates. of the Corps’ floodgate project, which has a benefit/cost ratio of The method in which the technical issue of sea level rise was only 1.3. The project team followed the Corps’ methodology in an addressed by the Corps was found inadequate by several state and effort to qualify for federal funds through the previously autho- federal agencies. There is considerable disagreement regarding rized project; however, this did not constitute a preference for the the future rate of sea level rise. The historical rate used by the Corps’ methodology. Maximizing net benefits is not necessarily Corps is far lower than potential future rates suggested by some the best option when resources are limited. It additionally aggre- experts ͑NRC 1987͒. The Corps addressed potentially higher rates gates benefits over all federal projects and does not necessarily by shortening the life span of the structure and by suggesting a reflect local interests and preferences regarding risk aversion. possible combination of increased frequencies of gate closures of Early development of the alternative plan was based on pre- greater duration. The NRC ͑1987͒ Case III scenario, presented for liminary analysis by the joint team, in which marginal benefit/cost sensitivity analysis by the Corps, resulted in a reduction of project ratios were considered for individual components of the plan. An life from 100 years to 35 years with an associated benefit/cost alternative structural plan ͑Option 1͒ formulated and rejected by ratio of 1.3. The Corps stated ͑USACE 1989͒ that for this sce- the Corps consisted of a combination of four local protection nario if a policy decision is made to retreat from more vulnerable plans ͑USACE 1989͒. Of these four, only the Revere Beach plan areas near the shoreline at the end of the modified project life the demonstrated significant net benefits, producing a benefit-to-cost project could simply be abandoned. However, this would occur ratio of 1.5 and annual net benefits of $890,000 in 1988 dollars. after further development in flood-prone areas, as well as recon- This represented 75% of the total net inundation benefits for the struction that may not be required to meet floodplain construction combined local protection plans with 28% of the total costs. The standards as a result of being removed from the FEMA- two other significant structural components are the previously au- designated floodplain. Losses associated with future flooding after thorized project for Point of Pines as well as the small tide gate in abandonment of the floodgate structure could therefore be inten- Revere. Both of these elements have high marginal benefit/cost sified under this scenario. No analysis that included this induced ratios. These structural elements alone have potential for address- increase of risk was presented. ing up to 41% of residential and 29% of total inundation benefits These potential responses to sea level rise involving increased for the Corps’ floodgate plan ͑Hayes 1995͒. The associated fully frequency and duration of gate closures ͑possibly 35 to 40 per funded cost for the structural elements is roughly 9% of the Corps

JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT © ASCE / JANUARY/FEBRUARY 2004 / 17 total regional floodgate plan’s cost ͑USACE 1993͒. rently recommended and implemented in federal programs for In the Corps’ floodgate plan, acquisition of most of the 1,660 flood insurance and floodplain management. Flood proofing of acre ͑672 ha͒ estuary was recommended to permit storage of in- existing structures, however, has been generally underutilized but terior runoff when the Saugus River tide gate would be closed. is now increasingly seen as a valuable alternative for flood hazard Because the Saugus River tide gates are not recommended in the mitigation. Flood proofing has been incorporated into several re- alternative plan, acquisition of the estuary is no longer justified cent regional flood control plans ͑SCS 1987, 1990, 1992, 1994; for this sole purpose. The development team however concurred Farmer 1994; USACE 1994͒ and was specifically mentioned in with the Corps’ recommendations for wetlands acquisition for ad- the Water Resources Development Act of 1996. ditional reasons cited in the feasibility report related to floodplain In the alternative plan, nonstructural approaches for residential management. Additionally, this element has significant environ- structures consist of wet floodproofing, dry flood proofing and mental benefits related to the health of the Saugus and Pines elevating flood-prone properties. Purchasing flood-prone proper- Rivers marsh, which would be realized under either the Corps ties is likely to have minimal use but has been included in the federally authorized plan or the alternative plan. These benefits plan. Relocation is similarly unlikely due to high costs and the have not been quantified in either the Corps’ 1989 feasibility lack of available higher ground. The analysis described herein study or in the alternative plan ͑Hayes 1995͒, beyond the calcu- focuses on the overall feasibility of a large-scale flood-proofing lation of the market value of acquired wetlands because of a program. Actual implementation would require working with in- general lack of tools for such analysis ͑Scodari 1990͒. They are of dividual homeowners. There is no guarantee that all eligible great interest to a variety of local, state, and federal groups and homeowners would participate in the program. The availability of have played an important role in the formulation of both plans. technical assistance and federal funds in an area known for flood Two specific components of the Corps’ floodgate plan, the problems is, however, expected to result in a high level of partici- floodgates and armament of Lynn Harbor, were rejected by the pation. interdisciplinary group because of environmental, fiscal, and policy concerns. Roughly 70% of the entire cost of the Corps’ floodgate plan ͑$114,000,000͒ is associated with a gated, flood- Wet Flood-Proofing Structures control structure across the mouth of the Saugus River. The over- In wet flood proofing, essential items, particularly utilities, are all benefit/cost ratio for the Corps’ plan is only 1.3, and it is not protected from floodwater that may enter the home. This technol- clear whether the increased benefits associated with the addition ogy involves either the construction of flood walls around items of the floodgates to the other components of the floodgate plan are or relocation of items to a higher floor or to a newly constructed greater than the associated increased project costs. Significant fi- platform. All utilities, especially circuit breakers and fuses should nancial resources are required for this portion that could possibly be raised above the 100-year flood elevation. Electrical outlets be better spent on other flood damage prevention programs with should either be elevated or else set on a separate circuit that can higher net benefits within the state. be shut off prior to a potential flood event. Benefit estimation for Under the Corps’ floodgate plan, 8,900 ft ͑2,713 m͒ of dikes wet flood-proofing techniques were based in part on discussions and seawall would provide protection to development and vacant with individuals at the Federal Emergency Management Agency lots along Lynn Harbor. Preliminary estimates of the local benefit/ ͑FEMA͒, the USACE National Flood Proofing Committee, cost ratio was 1.35 ͑Hayes 1995͒. However, estimates of inunda- USACE Institute for Water Resources, and the NED of USACE. tion benefits in Lynn associated with this calculation have been A recent FEMA Region 1 pilot program ͑FEMA 1993͒ used wet questioned due to discrepancies between current Corps’ estimates flood proofing to reduce flood damages in most of the 86 flood- ͑USACE 1989͒ of damages excluding nonphysical damages to proofed homes. The average cost per home was $2,218 in 1994 commercial property in Lynn associated with a recurrence of the dollars. Most notable was the fact that the total cost of the project Blizzard of ’78 ͑$62,500,000 in 1994 dollars͒, and total direct and was only 59% of the estimated benefits associated with reduced indirect damages actually reported from the Blizzard of ’78 for damages from a single storm that occurred in December of 1992. the entire city of Lynn ͑$19,900,000 in 1994 dollars͒ in a postdi- The 1993 pilot program demonstrated the potential of new tech- saster reconnaissance study performed by the Corps ͑USACE niques not considered in the Corps’ earlier analysis ͑USACE 1979͒. The large industrial facilitiy owned by General Electric in 1989͒. Lynn was shut down before high tide and state roads were only for use by emergency vehicles. This suggests that much of the estimated losses in Lynn may be attributable to indirect costs. Dry Flood-Proofing Structures Therefore, it is unclear whether positive net benefits can be asso- Dry flood proofing involves sealants and enclosures around open- ciated with armament in Lynn. Additionally, the area to be pro- ings that keep water from entering the structure. Only passive tected is currently not heavily developed and new development in methods that require no intervention by homeowners were con- the area will be protected to the 100-year level of protection under sidered for residential property. A sewer check valve or one-way current National Flood Insurance Program ͑NFIP͒ regulations. flap is installed in the sewer line to permit outgoing sewage to Furthermore, negative environmental impacts are associated with flow during nonflooding conditions. The flap is held shut during the construction of these features. flood conditions by pressure.

Flood Proofing Residential Structures in Alternative Elevating Structures Plan Existing structures are elevated so that their first-floor elevation is Previous efforts to mitigate flood damage in the United States above the elevation associated with the 100-year flood as deter- have relied extensively on ‘‘structural’’ solutions intended to re- mined through previous analysis by the Corps ͑USACE 1989͒. duce flood depths in developed areas by the construction of large Elevation costs depend on the height as well as the type of house hydraulic structures. Some ‘‘nonstructural’’ measures are cur- to be raised.

18 / JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT © ASCE / JANUARY/FEBRUARY 2004 Each commercial and industrial property would be given a recommended nonstructural option with approximate costs. More expensive options may be made available under the assumption that the owner takes on any additional associated costs. This increased flexibility would help to optimize the plan by allowing commercial and industrial property owners to make decisions consistent with their judgment of market effects. Individual flood-proofing recommendations for structures in the 100-year floodplain ͑excluding General Electric͒ appear in Fig. 2. Those structures indicated as being in the floodplain are those having a damage elevation ͑elevation of first opening͒ below the 100-year flood level based on the frequency stage Fig. 2. Protection of buildings in 100-year floodplain curves presented in the ‘‘Feature Design Memorandum’’ ͑USACE 1993a͒. Residential structures identified as being in the floodplain are categorized according to the most cost efficient technology Purchase of Structures that can be considered feasible. The recommendations are based on estimates for the purpose of evaluating the feasibility of a Severely damaged or highly vulnerable structures in flood-prone comprehensive flood risk management plan. Final recommenda- areas will be purchased from voluntary sellers at fair market val- tions for flood proofing individual structures should be based on ues. Purchased structures will then be demolished followed by information gathered at site visits at the time of program imple- site work to establish more appropriate future use ͑open space or mentation. recreational͒ of the flood-prone land. Structures identified as ‘‘Unresolved’’ ͑Fig. 2͒ represent residential structures that do not have specific recommendations as- Relocation sociated with them. Some of these structures are unresolved be- Relocation is usually more expensive than raising buildings because the data did not match the assumptions of the computer cause it involves lifting and transporting a building to a new code used in the analysis. The vast majority of the unresolved location. structures were marked unresolved because they did not demon- strate positive net benefits for any of the technologies that were Additional Techniques for Commercial physically feasible under the assumptions and methodology used and Industrial Property in the computer code. Fig. 3 shows the percentage of unresolved structures as a function of flood depth. For 75% of these struc- A nonstructural flood-proofing program for commercial and in- tures, the flood depth is 0.305 m or less. Therefore, the negative dustrial property should incorporate a wider variety of choices. net benefits are not surprising.

Fig. 3. Percent unresolved structures with elevations exceeding various ﬂood depths

JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT © ASCE / JANUARY/FEBRUARY 2004 / 19 Fig. 4. Ratio of present value to annual value for various interest rates

Methodology of the Flood Prooﬁng Computer Code

Recommendations for flood proofing were based on the results of a structure-by-structure analysis using the computer program SID–OPT developed for this project. There are few computer codes designed for benefit/cost analysis of flood proofing for individual structures ͑FEMA 1995a,b; USACE 1992͒ and none are oriented toward large-scale feasibility studies involving numerous structures. One reason cited by the Corps for the limited study of nonstructural Option 2 was the lack of an appropriate computer Fig. 5. Dry flood proofing of home in Lynn Zone 1 ͑benefits in program ͑USACE 1989͒. The Flood Damage Analysis ͑FDA͒ thousands of $1986 one family, two story, unfinished basement͒ Package ͑USACE 1988; USACE 1990͒, which was used in the Corps’ study, is the primary tool used for inundation benefit analysis by the Corps. This package can be used to analyze inundation reduction benefits associated with dry flood proofing, el- ϱ ϭ ͓ ͑ ͒Ϫ ͑ ͔͒ ͑ ͒ evating, and relocation. It does not have the ability to optimize Expected Benefit ͵ DE y DFP y f y dy 0 benefits on a structure-by-structure basis and, therefore, underes- ϭ ϭ timates potential flood-proofing benefits for large projects. Addi- where f (y) probability density function; DE damages under ϭ tionally, it cannot evaluate benefits associated with wet flood existing conditions; DFP damages under flood-proofed condi- proofing. tions; and yϭflood stage. The SID–OPT code reads a structural inventory input file that Benefits are then transformed from annual values into present has been formatted for use with USACE’s FDA Package. Data values, assuming a project period of 100 years and an interest rate from the Corps’ previous analysis of structural options were pro- of 8.25%. As seen in Fig. 4, the ratio of present value to annual vided in this format. The Corps’ extensive survey of the area value depends primarily on interest rates rather than life span, for includes the address, building type, elevation, damage curves, and life spans over 40 years. The actual change in damages: DD ϭ Ϫ ͑ ͒ approximate value of each structure. SID–OPT then searches for DE DFP , or Delta Damage function DD function , is calcu- structures that would be flooded by the 100-year flood, tests vari- lated as a function of depth at each structure based on the type ous wet flood-proofing options for those structures, and accepts and height of flood proofing, the first-floor elevation and the el- the least expensive solution with positive net benefits. SID–OPT evation of the first opening, and the depth damage curve for the prints summary files with flood-proofing recommendations and structure. associated benefits and costs, as well as depth of flooding associ- As an example of an individual damage reduction curve used ated with the 100-year flood for all addresses in the database. in the study, the curve associated with dry flood proofing for an Additionally, it writes lines that can be inserted into FDA data individual structure in the inventory is presented in Fig. 5. files for testing dry flood proofing for verification. Three functions to test the three flood-proofing options include Wet Flood Proofing elevating structures, wet flood-proofing structures, and dry flood- proofing structures. The path ultimately taken in the search for the For wet flood proofing, the DD function is based on the assump- minimum cost solution depends on the design flood elevation, the tion that the utilities are raised to the elevation of the 100-year elevation of the first floor, and the elevation at which water can flood. Emergency costs, based on the FEMA Region I benefit/cost first enter the structure ͑e.g., basement window͒. analysis used in the recent FEMA minimization program, were Expected benefits from flood proofing are calculated based on added as savings incurred when the otherwise damaged utilities numerical integration of the differences in damages ͑with and were protected. Each DD function has $2,990 in 1986 dollars/ without flood proofing͒ over probability family added for emergency costs foregone because of wet flood

20 / JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT © ASCE / JANUARY/FEBRUARY 2004 Table 1. Benefit Comparison between FDA and SID–OPT a a ͑ ͒ Zone Data file Number of flood-proofed structures FDA benefits SID–OPT benefits Deviation % Saugus 1 sa1–r–e–.s 34 80,920 78,746 2.8 Lynn 1 lyzo1rm.s 96 155,760 176,403 11.7 Revere 2B re2br–t6.s 28 114,630 107,730 6.8 Total 158 80,920 78,746 3.2 aAnnual 1986 dollars. proofing. This is based on the estimates made by FEMA for their The costs of elevating a single residential structure would pilot program and reflect average costs/person ͑instead of family͒ likely range from $30,000 to $40,000 in 1994 dollars. For this excluding replacement costs for damaged items and repair costs analysis, a value of $35,000 in 1994 dollars was used for all that were excluded because the Corps’ data were used to represent structures. direct damages. Utility damage curves based on the 16 ‘‘typicals’’ Residential depth damage curves were developed for each used to depict residential structures are taken directly from the ‘‘typical structure,’’ excluding damage to the property exterior, Corps’ FDA data files. Cost estimates of wet flood proofing are based on data provided by the Corps. SID–OPT detects the ‘‘typi- taken directly from FEMA’s minimization pilot program ͑FEMA cal’’ code number associated with each structure and uses the 1993͒. appropriate depth damage curve. Frequency stage curves used in Community search, rescue, and evacuation and emergency the development of preliminary flood-proofing recommendations food, clothing, shelter, and medicine are excluded because wet are those presented for existing conditions in the Corps’ Feature flood proofing is not expected to affect evacuation efforts during Design Memorandum No. 2 ͑USACE 1993͒, with the exception of the emergency. These emergency costs or the ‘‘cost of being a Zone 1 in Revere. Frequency depth curves used for Zone 1 of flood victim’’ are different from those estimated by the Corps’ Revere were taken from the Feature Design Memorandum No. 2 methodology. The Corps associated ‘‘out of pocket expenses’’ for for the ‘‘modified’’ condition in which the effect of reduced flood- each residential structure type and then separately lumped to- ing caused by the installation of a small floodgate is reflected. gether emergency costs paid out by state, federal, and other organizations. Savings of emergency costs paid out by state, federal, and other organizations have not been listed as a benefit associ- Verification and Sensitivity of the Flood-Proofing ated with the dry flood proofing and elevating techniques applied Computer Code to residential structures. Verification of the SID–OPT code developed at Rutgers Univer- sity was performed through a direct comparison of dry flood- Dry Flood Proofing proofing benefits computed using the FDA package and those The DD function simply reflects those damages to the entire computed by SID–OPT for three data files. The three files repre- structure that would have occurred if the structure had not been sent residential structures located in single hydrologic zones lo- flood proofed to an elevation 0.9 m above the first structural cated in Saugus, Revere, and Lynn, Mass. Only dry flood- opening. Because flood-proofing costs vary widely structure-to- proofing benefits are evaluated and compared because the FDA structure, a fixed figure of $13,200 in 1988 dollars per structure package does not compute benefits for wet flood proofing and was developed early in the study based on the Corps’ estimates computes benefits for elevating structures using assumptions in- for flood proofing basements in the 1989 feasibility report. These consistent with those used in the SID–OPT program. figures appear high in comparison to those used in the FEMA For each data file used, the structures recommended for flood minimization pilot program ͑FEMA 1993͒. Estimation of costs proofing by SID–OPT were selected in the Structural Inventory associated with exterior minimization based on 16 implementa- Damage Analysis ͑SID͒ database for dry flood proofing to an tions appear to range between $3,000 and $6,500 in 1993 dollars. elevation of 0.9 m above the first opening. The FDA benefits For the purposes of this analysis, two different costs are associ- represent the difference in expected annual damages calculated ated with dry flood proofing of a structure. The greater is $13,200 using the FDA package’s SID and Expected Annual Damages in 1988 dollars and was used whenever the 100-year flood eleva- ͑EAD͒ programs with and without flood proofing of the specified tion was greater than the first-floor elevation of the structure. The structures. Results are presented in Table 1. lesser cost, employed when the 100-year flood elevation is below For the three data files, the deviations in calculated benefits the first-floor elevation of the structure, is based on the average of range from 2.8 to 11.7%, and the average deviation and standard the Corps’ estimate and the cost of wet flood proofing the struc- deviation were 3.2 and 10%, respectively. Three reasons have ture as described in the previous section. been identified for these deviations. First, the numerical integration methods of the FDA package and SID–OPT differ slightly. Second, the truncation of depth damage curves related to flood Elevating proofing and start of damage is performed differently. Third, loss The damage reduction curve for elevating structures is based on of information occurs within the SID code due to aggregation of the most likely implementation scenario for elevating a structure depth damage curves for structures in a zone before performing with a basement, i.e., combined with wet flood proofing of a the integration. basement. The three options for elevating a structure with an ex- The FDA package uses a higher accuracy Gaussian quadrature isting basement are wet flood proofing ͑least expensive and gen- approach that accounts for subtle changes in curvature of the erally implementable͒; dry flood proofing ͑more costly and not damage-frequency relationship between two points; whereas, the ͒ ͑ always implementable ; and backfilling basement generally un- SID–OPT program uses an average value between individual desirable to homeowners͒. points. Because the frequency range over which the numerical

JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT © ASCE / JANUARY/FEBRUARY 2004 / 21 integration occurs is discretized identically using 100 elements, the predicted deviation in results because of the first reason was expected to be small. The truncation of depth damage curves differ at elevations such as at the top of flood proofing, at the first opening, and the start of damages. The SID program of the FDA package simply removes the damages at the closest node, leaving a depth damage curve along that distance as an interpolation between the trun- cated point and the adjacent point. In contrast, the truncation of depth damage curves in SID–OPT is accomplished by adding points at the exact point of truncation and at a point 0.01 ft above the truncation point causing a ‘‘sharp’’ cut in the depth damage curve. These sharp cuts can be clearly seen in Fig. 5. In general, because this difference would result in slightly increased benefits for the start of damages and slightly decreased benefits associated with exceedence of the flood-proofing elevation in the SID–OPT program, the net result, after weighting with the estimated probability ͑higher for the lower elevations͒, would tend toward slightly greater benefits for SID–OPT in comparison to the FDA package. The third source of deviation is associated with the shifting of the damage points along the stage axis in order to align an individual structure’s curves with the curve used for aggregation. This process is depicted in the top panel of Fig. 6, using data taken directly from output files generated by the FDA package for a structure located in Saugus Zone 1. Because damages are inte- grated for each individual structure in the SID–OPT code, no aggregation and no shifting of the flooding stage axis are needed, thus reducing one potential loss of accuracy. These factors combined create an increase of expected annual benefits from $603 using FDA code to $728 using SID–OPT code in 1986 dollars. When an identical ‘‘aggregate’’ depth damage curve is used instead of the usual SID OPT generated curve, – Fig. 6. Comparison of depth damage curves for home on Spencer SID–OPT calculated $606 for the same scenario. Thus, a discrepancy of approximately 0.5% resulted from omitting the use of St., Saugus, Mass. splines and Gaussian quadrature, and a discrepancy of 21% resulted from different manipulations of the depth damage curve associated with truncation and aggregation. The results from the time of implementation, the primary investment in overhead costs limited verification analysis indicate that these combined sources already will have been made. At that point, only marginal net of deviation are not significant, particularly in light of the high benefits should affect decisions at individual structures, i.e., net benefit-to-cost ratio observed for most of the residential flood- benefit calculations without imposing overhead costs. proofing analysis. The results are relatively more sensitive to han- Because the Corps used indirect costs in their cost analysis for dling of the depth damage relationship than they are to the actual flood proofing at individual structures in their 1989 study, sensi- integration method employed because of the high resolution used tivity analysis of the preliminary recommendations to contin- in both programs. gency and overhead costs incorporated in the structure-by- In the Corps’ feasibility study, indirect costs were added to structure analysis was performed and is presented in Fig. 7. These costs for each structure before the net benefits were calculated in results, generated by the SID–OPT code, indicate that recommen- order to ascertain the cost-effectiveness of flood proofing. These dations, benefits, and costs are not greatly sensitive to the indirect costs, particularly that of overhead, have been excluded from the cost factor used. As expected, the number of ‘‘unresolved’’ struc- structure-by-structure analysis, and a figure of 30% is used for the tures increases, however, even for an indirect cost factor of 60%, entire flood-proofing plan after testing for positive net benefits at this increase is relatively low ͑11% of total structures in flood- each structure. The inclusion of a contingency cost may be desir- plain͒. Similarly, costs increase and benefits decrease but not sig- able at each structure at the time of implementation in order to nificantly. The marginal benefit/cost ratio for total residential reflect the uncertainty involved in costs associated with the work flood proofing falls from 4.2 to 3.9 when an indirect cost factor of to be performed. This factor should be relatively small, however, 60% is used. because the information gathered during the site visit should reduce the uncertainty substantially. Uncertainty for the entire plan during this feasibility study is higher, however, and a contingency Flood Proofing of Nonresidential Property cost plays a more important role in safeguarding against gross in Alternative Plan errors in the plan. Overhead costs are applied to the plan as a whole because they involve the organization and implementation Structure-by-structure analysis of costs and benefits at nonresi- of a program to be offered to individual homeowners regardless dential structures was not within the scope of this project because of whether they ultimately qualify and agree to participate. By the of the wide variability in both flood-proofing options, costs, and

22 / JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT © ASCE / JANUARY/FEBRUARY 2004 At the GE plant in Lynn, dry flood proofing is recommended because the majority of manufacturing operations are performed at ground elevation. Flood-proofing costs at GE, estimated to be $630,000, were based on the review of costs at several large manufacturing facilities. This value lies between the lowest ͑$500,000 based upon dry flood proofing͒ and the highest ͓$1,704,000 for a ring wall ͑USACE 1989͔͒. The stipulation that individual elements of the plan only be implemented if positive net benefits are associated with them suggests that the benefits will at least equal the costs. Annual benefits associated with 0.9 m of flood proofing of structures at GE were estimated as $559,400 in 1994 dollars using the Corps’ EAD computer code. Estimation of benefits associated with flood proofing of nonresidential property other than GE has not been performed because the benefits will depend on the flood proofing techniques implemented. Assuming indirect costs of 30%, the re- sulting total estimate of a lower limit for commercial benefits is $1,334,170/year. This can be considered a conservative estimate when considering the Corps’ estimate of over $2,300,000/year in nonresidential damage reduction under an Option 3 floodgate plan designed for the 100-year level of protection.

Fig. 7. Sensitivity of recommendations and Economics for Residen- Conclusion tial Flood Proofing—Saugus River Coastal Flood Risk Reduction Plan ͑cost and benefits reported in 1994 dollars͒ The greater flexibility accompanying the EOEA/UHI/Rutgers combined structural and nonstructural approach is expected to increase net economic benefits over the limited nonstructural ap- benefits. Costs and benefits for implementing a large-scale flood- proach ͑Option 2͒ developed and rejected by the Corps during proofing plan are instead estimated on a conservative basis using their feasibility study ͑USACE 1989͒. This advantage is aug- relatively high cost and low benefit estimates. Therefore, the final mented by the incorporation of a wider variety of nonstructural figures are somewhat ‘‘qualitative’’ and are intended to be used techniques with lower associated costs. Additionally, lower costs primarily to evaluate the overall economic feasibility of the plan are expected for traditional nonstructural techniques considered as a whole. by the Corps based on updated and augmented cost information. The SID–OPT program establishes recommendations for non- Development of a computer program for optimizing the nonstruc- residential structures based solely on flood depth. Wet flood tural portion of this plan was essential. Testing of the SID–OPT proofing is recommended for a small portion of commercial struc- program demonstrated the sensitivity of results to programming tures in the 100-year floodplain for which the 100-year flood el- choices regarding the handling of damage curves. evation is below the first floor. The vast majority of commercial The estimates of the cost of the alternative plan appear in structures in the 100-year floodplain ͑83%͒ have 100-year flood Table 2 and represent approximately one-third of the total first levels above the first floor but less than 3 ft above the first open- cost estimated for the Corps’ floodgate plan. Benefits of the alter- ing, making traditional dry flood proofing the most likely option. native plan are estimated at a value of $7,872,070 and appear in However, some of these could receive some form of wet flood Table 3. This estimate does not include additional inundation re- proofing, depending on the type of building and the type of busi- duction benefits associated with sea level rise, which accounted ness. At 46% of the 252 structures recommended for traditional for 16% of the inundation benefits calculated for the federally dry flood proofing, the estimated 100-year flood elevation is 1 ft authorized plan. The alternative plan would meet state objectives or less above the first opening. Structures that would need to be for flood-risk reduction in the study area in what would appear to flood proofed higher than 0.9 m would require other forms of be a significantly more cost-effective manner. Similarly, opera- flood proofing, such as elevating or surrounding them with a flood tions and maintenance costs would be significantly less. The an- wall or berm. nualized first cost is $3,292,640 in 1994 dollars. This results in an Cost estimates for flood proofing nonresidential structures in overall benefit-to-cost ratio of 2.5 and annual net benefits of at the Saugus River floodplain are based on the Quantity and Cost least $4,680,430 in 1994 dollars. A direct comparison of the Curves for Flood Control Measures of the Passaic River Basin, Corps’ floodgate plan and the alternative plan appears in Table 4. New Jersey ͑USACE 1980͒. Flood-proofing costs were estimated Although total benefits are lower, net benefits are significantly for 120 commercial structures in Lynn based on the area of each higher than the Corps’ floodgate plan because of substantially building identified on maps provided by the New England divi- lower costs. sion of the Corps. This resulted in an average flood-proofing cost In the alternative plan, structures are protected in two ways. In of $25,080/structure in 1994 dollars without overhead or contin- some areas, shoreline protection and other structural solutions re- gency costs. Through extrapolation, the cost estimate for flood sult in a reduction of the estimated 100-year flood elevation. This proofing the 288 nonresidential structures ͑excluding GE͒ was type of flood protection is referred to as ‘‘flood reduction’’ for $7,223,040. Of the 290 nonresidential structures to be flood- those structures that are no longer in the 100-year floodplain be- proofed, 53% are in Lynn, 10% are in Saugus, and 37% are in cause of these effects. Other structures, still in the 100-year flood- Revere. plain are protected by ‘‘flood proofing’’ if some form of flood

JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT © ASCE / JANUARY/FEBRUARY 2004 / 23 Table 2. Estimate of Project Costs Table 3. Estimate of Benefits of Project Operations Expected annual and Type of benefit benefits in 1994 dollars First costa maintenance Reduced flooding in Revere Beach Areaa Not estimated Project element ͑$1994͒ ͑dollars͒ Reduced emergency costs for dry flood Not estimated b Sales Creek tide gate—Revere 22,200 900 proofing and elevating structuresb c Augmented ponding area—Revere 250,600 860 Increased benefits associated with sea level rise Not estimated Dune restoration, revetments and wall 5,155,600 12,880 Environmental benefits associated with At least 480,000 d,e modification—Point of Pines purchase and protection of wetlandsc f d Park dike —Revere 3,134,500 14,340 Flood-proofing commerciald At least 1,334,170 Wet flood proofing 540 residential structures 1,674,700 Flood-proofing residencese 3,702,050 Dry flood proofing 383 residential structures 5,649,000 Flood risk reduction—Point of Pinesf 1,660,000 Elevation of 96 residential structures 3,359,500 Reduced shoreline protection costs—Point 113,800 Flood proofing of 288 nonresidential 7,223,000 of Pinesf structures Recreational benefits—park dikef 477,250 Flood proofing at the General Electric plant 631,000 Reduced flooding, Revere Zone 1—small 104,800 Contingency and overhead on flood 5,561,200 tide gateg proofing ͑30%͒ Total At least 7,872,070 g Purchase of wetlands 6,021,400 None aFrequency depth curves needed for analysis. Subtotal 38,682,700 28,980 bEmergency costs currently used reflect Corps’ estimate of victim out of Enhanced floodplain management and enforcement pocket expenditures. of existing floodplain regulations cBased on market value of wetlands. Comprehensive plan to facilitate owners of dBased on cost estimates of flood proofing and benefits calculated for infrastructure in dealing with flood risks flood proofing at GE plant using EAD program. a These values do not include cost of interest during construction. eBased on SID OPT results. b – A5Јϫ5Ј tidal gate as described by USACE ͑1989͒. fBased on 1989 USACE feasibility study. cThe ponding area, as described by USACE ͑1989͒, won’t involve dredg- g Based on 1989 USACE feasibility study and corroborated by SID–OPT ing and/or excavation. program at Rutgers. dConcerns have been raised regarding the potential for encouragement of development. Thus the applicability of Executive Order 181 must be development team, their previous engineering work has been addressed. e heavily relied on, and their cooperation in providing information Redesign of protection measures at Carey Circle required in order to to the team has been invaluable. minimize environmental impacts. Dune construction recommended for ͑ ͒ beach area between General Edwards Bridge and proposed location for The interdisciplinary study Hayes 1995 has been instrumen- the Corps’ selected floodgates in lieu of seawall originally proposed in tal in subsequent decisions related to the federally authorized original detailed project report. project, as well as local projects in the area. The nonfederal por- fPossible design modifications are in order due to Revere Beach renour- tion of funding for the floodgate project was never authorized. ishment project. Although there has been discussion regarding participation by the gSome of these wetlands have already been acquired by MDC. Corps of Engineers in various components of the alternative plan, none has so far occurred. Portions of the alternative plan have, nonetheless, been moved forward through a combination of other federal, state, and local funding mechanisms. These include the proofing has been recommended based on an individual benefit- purchase of tidal wetlands, repair and upgrade of existing tide- cost analysis. As seen in Table 4, 27% of the structures protected under the alternative plan are protected via ‘‘structural’’ methods while 73% receive flood proofing. The alternative plan does not Table 4. Comparison of Corps’ Floodgate Plan and Alternative Plan contribute to sea level rise problems by encouraging development Corps’ floodgate Alternative in areas that could later become flood prone if the Corps’ flood- plan plan gate were to be constructed and then abandoned after 35 years. Protection for residential and commercial interests hardest hit by Fully funded first cost in 1994 $114,000,000 $38,682,700 direct exposure to wave run up from Broad Sound and for loca- dollars tions in a study area where public safety is of greatest concern Yearly maintenance and operations $270,000 $28,980 relies primarily on structural measures. The alternative plan re- cost duces the likelihood of adverse environmental impacts and pro- Portion of plan costs associated 87% 27% vides flood protection to a level consistent with the National with structural measures Flood Insurance Program. Annual benefits in 1994 dollars $13,390,000 $7,872,070 The involvement of representatives from state agencies in the Portion of buildings protected in 100% 80% development process has increased the plan’s potential to incor- 100-year floodplain porate region specific opportunities and experience. The process Benefit/cost ratio 1.3 2.5 itself serves as an example of combining sponsor preferences and Level of protection SPNa and 100-year 100-year storm expertise with federal resources typically employed for regional storm problems that surpass the resources of an individual state. Al- Annual net benefits in 1994 dollars $3,230,000 $4,680,430 though the Corps of Engineers has not worked directly with the aStandard project northeaster with exception of Point of Pines.

24 / JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT © ASCE / JANUARY/FEBRUARY 2004 gates and other drainage improvements, revisions to local flood Hayes, B. D. ͑1995͒. ‘‘Coastal flood risk reduction plan—Saugus River hazard bylaws, and a new tide gate at Sales Creek. Two commu- and tributaries.’’ Report submitted to Massachusetts EOEA, Rutgers nities have received flood mitigation grants from FEMA, and re- Univ., Piscataway, N.J. ͑ ͒ ͑ ͒ petitive loss data critical to FEMA funding have been updated. National Research Council NRC . 1987 . ‘‘Committee on engineering Participation in FEMA’s hazard mitigation programs has been implications of changes in relative mean sea level.’’ Responding to changes in sea level, National Academy Press, Washington, D.C. particularly important because it increases the likelihood that fed- Platt, R. H., Miller, H. C., Beatley, T., Melville, J., and Mathenia, B. G. eral funding of the most cost-effective flood-proofing opportuni- ͑1992͒. Coastal erosion, has retreat sounded?, Institute of Behavioral ties will occur. Science, University of Colorado, Boulder, Colo. Typical of most large-scale water-resources plans, progress to- Scodari, P. F. ͑1990͒. Wetlands protection: The role of economics, Envi- ward implementation has been less than speedy. The study was ronmental Law Institute, Washington, D.C. reviewed and found to be sound in 2000. Because funding from Soil Conservation Service ͑SCS͒. ͑1987͒. Bailey Creek flood prevention the federally authorized plan cannot be transferred directly to the RC&D measure plan and environmental assessment, Soil Conserva- alternative plan, the plan has not been pursued on a comprehen- tion Service, Conn. sive level. Instead, the most cost-effective and implementable Soil Conservation Service ͑SCS͒. ͑1990͒. Yantic River Watershed: Water- portions have moved forward because of their inherent advan- shed plan/environmental assessment, Soil Conservation Service, tages. Conn. Soil Conservation Service ͑SCS͒. ͑1992͒. Bailey Creek flood prevention measure RC&D fact sheet, Soil Conservation Service, Conn. Soil Conservation Service ͑SCS͒. ͑1994͒. Watershed plan— Acknowledgments Environmental assessment for upper french broad river watershed, Soil Conservation Service, N.C. Support for this project from the Executive Office of Environ- U.S. Army Corps of Engineers ͑USACE͒. ͑1979͒. Blizzard of ’78, coastal mental Affairs of the Commonwealth of Massachusetts is grate- storm damage study, New England Division, Waltham, Mass. fully acknowledged. The cooperative efforts of team members U.S. Army Corps of Engineers ͑USACE͒. ͑1980͒. Quantity and cost from the five departments of EOEA and from the University of curves for flood control measures, New York District, New York. Massachusetts were essential to the work presented in this paper. U.S. Army Corps of Engineers ͑USACE͒. ͑1983͒. Economic and environ- Richard Thibedeau, the state hazard mitigation officer, is recog- mental principles and guidelines for water and related land resources nized for his innovation and leadership. Cooperation from the implementation studies: NED benefit evaluation procedures—Urban New England Division of the USACE as well as other individuals flood damage, Section IV, Washington, D.C. U.S. Army Corps of Engineers ͑USACE͒. ͑1988͒. Flood damage analysis at FEMA and the USACE was also greatly appreciated. package, Hydrologic Engineering Center, Davis, Calif. U.S. Army Corps of Engineers ͑USACE͒. ͑1989͒. Saugus River and tributaries flood damage reduction study, Lynn, Malden, Revere and References Saugus, Massachusetts, Waltham, Mass. U.S. Army Corps of Engineers ͑USACE͒. ͑1990͒. Flood damage analysis Farmer, W. H., Hinton, M. J., and Webb, J. E. ͑1994͒. Development of a package on the microcomputer: Installation and user’s guide, Hydro- public law-566 nonstructural plan to reduce flood damages in the logic Engineering Center, Davis, Calif. Upper Frend Broad River, North Carolina, Soil Conservation Service, U.S. Army Corps of Engineers ͑USACE͒. ͑1992͒. Computer program N.C. users manual for the nonstructural evaluation program, Sacramento Federal Emergency Management Agency, ͑FEMA͒. ͑1993͒. Region I, in- District, Sacramento, Calif. dividual and family grant minimization pilot program, Washington, U.S. Army Corps of Engineers ͑USACE͒. ͑1993͒. ‘‘Hydrology and hy- D.C. draulics, Saugus River and tributaries, flood damage reduction Federal Energency Management Agency, ͑FEMA͒. ͑1995a͒. Benefit-cost project, Lynn, Malden, Revere and Saugus, Massachusetts.’’ Feature program, coastal A-zone flood model, Washington, D.C. Design Memorandum No. 2, Waltham, Mass. Federal Emergency Management Agency, ͑FEMA͒. ͑1995b͒. Benefit-cost U.S. Army Corps of Engineers ͑USACE͒. ͑1994͒. Floodproofing technol- program, coastal riverine flood model, Washington, D.C. ogy in the Tug Fork Valley, Washington, D.C.