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..... G’~..... ON 7VI~39 APPENDIX A

HYDROLOGY

TABLE OF CONTENTS

3 Paragraph Title 5 5 SECTION I - GENERAL A-1 3 A-1 PURPOSE AND SCOPE A-I A-2 PLAN OF IMPROVEMERT A-I

SECTION II - BASIN CHARA6"fERISTICS A-I

A-3 LOCATION A-I A-4 TOPOGRAPHY A-I A-5 TRIBUTARIES A-2

SECTION III - CLIMATOLOGY A-2

~S A-2 PRECIPITATION A-2

SECTION IV - STORM ANALYSES A-3

A-8 MAJOR STORMS A-3 A-9 STANDARD PROJECT STORM A-3

a. Definition A-3 b. Storm transposition A-3

A-10 PROBABLE MAXIMUM STORM A-4

SECTION V- STREAMFLOW AND FLOOD ANALYSES .A-5

A-II STREAM-GAGINGSTATIONS AND RECORDS A-5 A-12 MAJOR FLOODS A-5 A-13 HYIROGRAPH DERIVATION A-6 A-14 STARDARD PROJECT FLOOD A-6

a. Definition A-6 b. Snowmelt A-6 c. Hydrograph determination A-7

A-i Table of Contents (cont’d)

Title

P/ZERVOIRS A-7

SECTION VI - FREQUENCY ANALYSES A-8

A-16 DISCHARGE-FREQUENCYANALYSES A-8 A-17 RAINFAI~ DEI~I~-DURATION-FREQUENCYANALYSIS A-8

SECTION VII - INTERIOR I~AINAGE A-8

A-18 PROBLEM AREA A-8 A-19 DESIGN CRITERIA A-9

TABLES

Nt~n~er

A-I Precipitationstations in or near Redwood Creek Basin A-2 Major storms of record A-3 Stream-gagingstations A-4 Annual maximum discharge, Redwood Creek at Orick and Smith River near Crescent City

A-5 Unit hyd~ograph data

PLATES l~er

A-I General map of basin A-2 Area - Elevation curves A-3 Normal annual precipitation A-4 Mass curves and isohyetal map, 18-20 January 1953 A-5 Mass curves and ~sohyetal map, 17-23 December 1955 A-6 Hydrologic data and unit hydrograph derivation, 20-25 December 1955

A-7 Hy~ologic data, 29 December 1954 - 2 January 1955 A-8 Hydrologic data, standard project storm-flood A-9 Discharge frequency curves A-IO Rainfall Depth-D~ratiom-Frequencycurves

A-ii HYDROLOGY P E SECTION ! - GENERAL

A A-1. PURPOSE AND SCOPE D E This appendix presents climatic and hydrologic d~ta for Redwood R O Creek Basin, California. It includes derivation of the standazd project flood as a basis for the design of local protective works, and develop- 3 5 ment of a dlscharge-frequencycurve used in the economic eval~tion of 5 the project. This appendix was approved by the Chief of Engineers by 5 2d Indorsement dated 2 ~rch 1960, to letter SPNGP~ dated 24 December 1959, Subject: Report on Standard Project Flood and Discharge Frequency Analysis, Redwood Creek Basin, Humboldt County, California.

A-2. PLAN OF IMPROVEMENT

The plan of improvementas presented in detail in the main report consists of channel improvementsalong the lower four miles of RegwOod Creek. The work would consist of channel rectification,levees and partial revetment. A trapezoidal~typechannel would be used through the urban and downstream rural areas and a system of setback levees with improved channel upstream from the mouth of Prairie Creek°

SECTION IX - BAS~ CHARAC~TICS

A-3. L~ATION

Redwood Creek located between 40°40’ and 41°30’ north latitude, drains an area of 283 square miles along the northern California coast. The basin is situated entirely within Humboldt County and flows directly into the Pacific Ocean at a point 50 miles south of the Oregon-California border° Orick, the only town in the basin, is located about three miles upstream from the mouth of ~dwood Creek and immediately downstream from Prairie Creek. A general map of the basin and locality is shown on Plate A-1.

A~. ~P~RAPHY

The basin consists of an elongated, mountainous,heavily wooded area which extends 56 miles along a northwest-southeastaxis with a maximum width of about seven miles. The elevation of the basin bounde~ies vary from sea level at the mouth to about 5~400 feet mos~lo at :the southeastern extremity of the basin. The most remote part of the basin lies 30 miles inland from the Pacific Ocean ~ud h~ an average windward barrier height of 2,500 feet and average leeward height of 3,500 feet. The area-elevatlon curve, shown on Plate A~2, indicates that approximately50 percent of the basin area lles above elevation 2,000 feet m.s.l° and five percent above elevation 4,000 feet m.s.l. In the lower four-mile reach, Redwood Creek has a fairly uniform slope of about eight feet per mile. The main stream has a watercourse length of about 64 miles. The only significant area of level land is located along the lower reaches of Redwood and Prairie Creeks.

A-5. TRIBUTAR7~

The long, narrow shape of Redwood Creek basin limits the size of 5most tributaries to about equal length and drainage area. Prairie Creek the only major tributary, has a stream length of about 12 miles, drains an area of about 40 square miles and joins Redwood Creek near river mile 3.5.

SECTION III - CLIMATOLOGY

A-6. TEMPERATURES

The lower coastal part of the basin is characterizedby mild, dry summers with frequent local fog and mild, wet winters. Temperatures recorded at Orlck-PralrieCreek Park are representativeof the lower part of the basin. This station has registered a high of 95 degrees Fahrenheit a low of 19°F., and has an average annual temperature of 51.9°F. The inland portion of the basin has little summer fog and a greater diurnal temperature range than 0rick. Temperaturesrecorded at Forest Glen, located on South Fork Trinity River about 52 miles south- east of Eureka, are representativeof inland areas. This station has an average annual temperatureof 51°F., a high of 105°F. t and low of -2°F.

A-7. PRECIPIT~ON There are two U. S. Weather Bureau precipitationstations within the basin. Orick-Prairie Creek Park has been in operation since 1937 and Blue Lake Redwood Creek since 1956. There are eight active U. S. Weather Bureau stations in or near the basin and 13 known private stations for which sufficient records are available to estimate normal annual precipi- tation. Station data are presented in Table A-1. Locations of hydrologic stations ar~ plotted on the Normal Annual Precipitationmap on Plate A-3. Generally, only ten or twelve official and private stations are available for construction of storm isohyetal maps. Basin orientation and topography exert a strong influence on areal distributionof precipitationan~ the pattern of normal annual isohyets is used as a guide in constructionof storm isohyetal maps. Ninety percent of the seasonal precipitationgener- ally occurs during the period, October through April, with monthly distri- bution as follows:

Normal Monthly Precipitationin Percent of Seasonal Total

Jul Au~ Sep Oct Nov Dec Jan Feb Yet Apr May Jun Total

0.7 0.4 1.5 9.7 12.9 16.7 14.3 14.7 13.6 7.2 5.9 2.4 lO0

A-2 The basin normal annual precipitationis estimated to be about 80 inches, _varying from 70 inches at the lower portion of the basin to over 85 inches across the central portion. The high seasonal total compared to coastal basins further south is due to more frequent preclpitationoccur- rencesratherthan to rainfall intensity. The 3-day rainfall value which can be expected to occur on the average of one year in ten is about ten inches, which is not significantlyhigher than values for the central and southern coastal areas of the State having normal annual precipitationof 30 to 40 inches. Precipitationin excess of 0.Ol~inch cam be expected to occur on the average of 120 days each year. Snowfall occurs at the higher 3 elevations but Is of relative minor importance since less than five percent 5 of the basin lies above elevation 4jO00 ~s.lo (the elevation above which 5 snowfall is significant)°Average annual snowfall at elevation 2,500 m.s.1. 7 is estimated to be about 50 inches and at 4,500 m.s.1, about lO0 inches. Snow cover seldom lasts very long or attains more than a foot or two in depth.

SECTION IV - STORM ANALYSES

A’8. MAJOR STORMS

Flood-producingrainstorms in this area result from the passage of one or more extratropical cyclones. These storms cause precipitationover large areas generally exceeding lO,O00 square miles. Most major storms occur during the period between November and April° The storms of October 1950 and November 1926 were exceptions. Although storms sometimes persist for five to ten days, the flood producing portions generally occur within a three-day period. Rainfall records show that notable storms occ~uu~d during February 1915, October 1950, January 1953 and December 1955. Isohyetal maps and mass curves at selected stations are presented on Plates A-4 and A-5 for the January 1953 and December 1955 storms. A +~bulation of daily rainfall at representativestations for the ten largest storms of record is presented in Table A-2.

A-9. STANDARDPROJECT STORM a. Definition. The standard project storm is define~ as the most critical storm of record within a region meteorologicallyhomogeneous to the basin under study, or the most critical storm of record in adjacent regions that can be reliably transposed to the subject basin. The transposition boundaries are limited only by the reliability of methods used to accomplish the transposition.

b. Storm transposition. General-type storms are more critical than the local-type over basins the size of Redwood Creek or over basins receiving high annual precipitation°The major storms, cited in paragraph A-8, were studied to determine which would be most critical when transposed over the Redwood Creek basin. The transposition m~thod generally used in studies on other basins within this District makes use of the ratio of storm precipita- tion to normal annual precipitation.Isopercentual maps were constructed for the storms of 19-24 February 1943, 27-30 October 1950, 17-20 December 1955, and 21-24 December 1955. The October 1950 storm, centered along the coast between Eureka and Klamath, dissipated rapidly as it traveled inland. Coastal stations received much greater rainfall than inland stations during the second part of the storm between noon on 28 October, and 9 a.m. on 29 October. The 72-hour rainfall depth from the transposed October storm was equal to that of December 1955, but time and areal distributionswithin the 72-hour period were not as critical as for the transposed December 1955 storm. The 21-24 December 1955 storm, centered in the Dos Rios-Laytonville area of the Eel River basin is consideredto be the most critical storm that has occurred in a region meteorologicallyhomogeneous with Redwood Creek basin. It was, therefore, adopted as the standard project storm for the subject basin. Transpositionwas accomplishedby the normal annual isoper- centual method discussed above. This transposition resulted in a 72-hour storm depth of 17.8 inches over the 278-square mile basin contributingto runoff at 0rick as compared with 12.5 inches that actually occurred during 21-24 December 1955. Distributionwithin the 72-hour period was based on an average of rainfal~recordedat Laytonville, Willits Howard Forest, and Lake Mountain. A hyetograph representingthis average is presented on Plate A-8. Upper air data recorded at Oakland and temperaturesat Blue Canyon (refer to Plate A-1 for locations) indicate the freezing level during 21-23 December 1955 ranged between 8,000 and 12jO00 feet m.s.1. Since the maximum elevation within Redwood Creek basin is about 5,400 feet m.s.1., the entire storm pre- cipitation was considered to have occurred in the form of rain. The isoper- centual map and transpositionregion are presented on Plate A-8.

A-10. PROBABLEMAX]Zg/M STORM

The probable maximum storm is a hypotheticalstorm that is considered to be the maximum probable from a meteorologicalanalysis based upon a pre- mise of optimum known conditions of dewpoint, air moisture, wind velocity and wind direction. Estimated probable maximum precipitation for the basin above two damsites considered during preliminarystudies was prepared by the HydrometeorologicalSection of the U. S. Weather Bureau. The estimated pre- cipitation in inches, used in studies at the ~Arthur Creek damslte,~for storm durations at 6-hour intervals from 6 to 72 hours are shown in the following tabulation:

Duration Percipitation ( ours) (Zches)

6 8.5 12 12, 3 18 15.1 24 17.2 3o 19.2 36 20.6 42 21.8 48 22.8 54 23.6 60 2}4.3 66 24.9 72 25.4 The probable maximum storm is used to determine the spillway design inflow hydrograph. Since the preliminary study of flood control by reservoirs proved uneconomical,the hydrograph resulting from this storm is not pre- P sented in this report° E S SECTION V - STREAMFLOW AND FLOOD ANALYSES C A D A-11. STRFAM-GAGSGSTATIONS AND RECORDS E R 0 Streamflow records for Redwood Creek are limited to the locations and periods as shown in Table A-3. The two gages in operation at the 3 present time are: (1) Redwood Creek at Orick and (2) Redwood Creek 5 5 Blue Lake. The Orick gage was in operation from 1911-13 and then was 9 placed in operation again in 1953o This gage records runoff from 278 square miles of the 283-square mile basin. The gage near Blue Lake was installed in 1953 and it gages runoff from 67°5 square miles. A staff gage near Korbel was in operation during 1911-13 which gaged runoff from an 82.8~square mile area by means of daily observed readings. In addition to these official gages~ the Corps of Engineers installed a staff gage at Orick in October 1949 for flood observation purposes. High- water marks of maximum stages during water years 1948 and 1950-1953 were obtained from a highwater mark painted on the Orick bridge for 1948 and from local volunteer observations of this gage after 1949. Discharges were estimated on the basis of rating curves developed after the recording gage was installed in 1953. The two existing gages are under the supervi- sion of the U. S. Geological Survey and records are published in the annual Water Supply Papers of that agency. Average annual runoff for the basin above the Orick gage during seven years of published record (1911-iS, 1953-58) is 854,700 acre-feet. The average annual runoff from Redwood Creek during a long representativeperiod is estimated to be about 750,000 acre- feet, representingan average depth of 50 inches over the basin. This estimate was based on a correlation analysis between gage records for Redwood Creek at Orick and Eel River at Scotia~ with adjustment to 45 years of record at Scotia. The following tabulation represents the typical monthly runoff regime in percent of annual runoff: Oct Nov Dec Jan Feb M~r GunJul Aug-Sep:: otal 0.7 5°5 15.2 2_1.6 22.6 16ol llo3 h.8 1o5 0°4 0.20.1 100%

A-12, NAJORFLOODS

Floods on Redwood Creek occur as the result of sustained rainfall for periods in excess of about 18 hours° Although precipitationin the form of snow often occurs at elevations above 4,000 feet mean sea level, it seldom accumulates to great depths and does not add significantlyto flood peaks. The long narrow shape of the drainage basin tends to sustain dis- charges and preclude floods of a flashy nature° Flooding of low lying areas occurs when the discharge at Orick reaches 25,000 to 30,000 c.f.s. Flood

A-5 peaks at Orick occur approximately12 hours after the center of mass of excessive rainfall. During major floods, stages exceed bahk-full for periods of 12 to 48 hours and generally recede to normal base flow within three days after rainfall ceases. The flood of December 1955 remained above 25,000 c.f.s, for 24 hours and during the standard project flood it is estimated that a discharge of 25,000 c.f.s, would be exceeded for about 48 hours. During the 1955 public hearing, the years 1889, 1921, 1927, 1935, 1937, 1950 mud 1953 were mentioned as years during which flooding occurred. Since the hearing, a major flood occurred in December 1955 which equalled the stage of the January 1953 flood. Both floods are rated at a peak discharge of 50,000 c.f.s. The Jaaua~y 1953 flood occurred prior to installationof the stream gage at Orick and the discharge is estimated on the basis of a highwater mark obtained from the Corps of Engineers’ staff gage installed in 1949 and rating curve developed since 1953. Long-time local residents have no memory of the floods of 1953 and 1955 having been exceeded° A tabulation of annual maximum discharges is presented in Table A-4.

A-13. UNIT HYDROGRAPHDERIVATION

A 2-hour unit hydrograph was derived for Redwood Creek at Orick by trial reconstructionof the 19-25 December 1955 gaged hydrograph. Basin rainfall was estimated from the isohyetal map drawn for the period 17-23 December 1955 and from mass curves of station rainfall as shown on Plate A-5. Hourly distributionwas based upon rainfall recorded at the U. S. Weather Bureau station at Kneeland lO SSE. This derivation and rainfall distribution is shown on Plate A-6. Verificationwas based upon reconstructionof the 30 December 1954 to 2 January 1955 gaged hydrograph as presented on Plate A-7. A unit hy~rograph for Prairie Creek (40-square mile area) was derived syathe- tically by comparison of basin characteristicswith Redwood Creek at Orick and lag relations determined in a study of the Eel River basin. The adopted unit hydrographsand basin data are presented in Table A-5 and Plate A-6.

A-14o STANDARD PROJECT ~D

a. Definition. The staudard project flood is a hypothetical flood which should approximatethe flood that would result under existing or specified conditions of basin development,if the standard project storm were to occur when hydrologic conditions are reasonably favorable for flood runoff.

b. Snowm~lt. Contribution to runoff from melting of an existing snow cover during the occurrence of the standard project storm is dependent upon a number of factors such as the initial snow covered area, density of the snowpack, wind speeds and air temperatureduring the storm, and various basin characteristics.Little observed data are available to evaluate the extent and depth of snow cover present during past storms over Redwood Creek. Basin elevation distributionindicates that snowmelt would make only a minor contributionto flood runoff. The general equation for snowmelt during rain periods as outlined in EM 1110-2-1406,"Runoff from Snowmelt", 5 January 1960, was used to compute the snowmelt during the maximum 6-hour period of rain and during the maximum 24-hour period° A forest cover factor of O. 5 and a wind and temperatureindex based on values recorded at Blue Canyon in the Central Sierras during the 2-1-24 December 1955 storm were adopted. This computationresulted in an average melt of 1o2 inches during the maxi~ P E mum 6 hours and 3.9 inches during the maximum 24 hours from a 28-square S mile contributingarea. It was assumed that all snow would be melted during C A the 24-hour period of maximum rainfall. This is in agreement with recom- D mendations for standard project initial snow cover conditions for this E latitude as presented in Chart 15~ ~Standard Project Rain-Flood Criteria", R O April 1957 (revised September 1958)~ U~ So Army Engineer District, Corps Engineers~ Sacramento~California. ~Zhis chart is based on a known critical 3 antecedent condition which existed on 1 February 19~o These assumptions 5 6 result in a basin-equivalentmelt rate of 0.0~-inch during the maximum 1 2-hour rain block. This low value indicates the minor importance of snow- melt comparedto the maximum rainf ~all depth of 2.28 inches during the same period.

c. ~ ~et~rmination. Loss rates as determined in the Decem- ber 1955 hydrograph reconstruction~ere adopted as representingconditions following an antecedent storm of moderate to heavy rainfall intensity and resultant runoff. These loss rates ~uged from OolO-inch per hour at the beginning of runoff excess to Oo08-inch per hour at the latter part of the storm. The hydrog~aph analyses of the December 1954 storm indicates a lower loss rate~ however~ the bas~u average rainfall estimate for this storm is not believed to be as reliable as that obtained from the December 1955 analyses. Rainfall was 20 percent above normal during November 1955 and 50 percent above normal during December 1955~ compared to 15 percent below normal during November 1954 and only 25 percent above normal during December 1954. During the three weeks prior to the December 1955 storm, basin aver- age rainfall was about lO inches~ and there were only three days without rain. Rainfall during the three weeks preceding the December 1954 storm totaled 3o 5 inches and there were lO day~ without rain. The two-hour unit hydrograph and base flow derived from the gaged hydrograph at Orick for the period 21-24 December 1955 is adopted a8 typical during major flood runoff. Similar loss rates are adopted for use with the Prairie Creek unit-hydro- graph. Peak discharge values for the standard project flood obtained from this procedure are as follows:

Redwood Creek at Orick 278 sqo mi. 77~000 c.f.s. Prairie Creek at mouth 40 sqo mi. 16~000 c.f.s. Standard project flood hydrographsare plotted on Plate A-8.

A-15. RESERVOIRS

There are no flood control or water conservationreservoirs within the Redwood Creek basin. A study showed that good control could be obtained from a reservoir at the McArthur Creek site~ located about four miles ~- stream from Orick~ as sho-ma on Plate A-lo Fram prelimina~j analys@s, it is concluded that the cost of provid~ !~-ood Oontrol storage would exceed estimated flood control benefits by a wide margin. SECTION VI - FREQUENCY ANALYSES

Atl6. DISCHARGE-FREQUENCYANALYSIS

Records of annual maximum discharge from 1953-60 were supplemented by estimatesbased on observed annual maximum flood stages at Orick’ for the years 1948, 1950-53o This record is too short to provide a reliable long- term trend of annual maximum discharge. A statistical correlation was made with coincident records for the Eel River at Scotia, Trinity River at Lewiston, Smith River near Crescent City, Van Duzen River near Bridgeville, and South Fork Eel River near Miranda, to determine the feasibilityof ex- tending Redwood Creek records on the basis of a station having a greater length of record. The best correlation was obtained with the Smith River near Crescent City which has 29 years of stresmflow records. The correla- tion coefficient for the common period of record (eleven years) is 0.5. Although this coefficientis rather low, it indicates a reliability of adjusted statistics equivalent to that obtainable from about 16 years of record° Other statistical data are presented in Table A-4. The magnitude of the standard project flood should give some indication of the magnitude of infrequent flood events° On the basis of the standard project flood magnitude and the apparent horizontal shift of the short-term versus long- term ~ccumulativefrequency curves at other Northern California coastal stations, the adopted frequency curve appears reasonable. The adopted curve departs slightly from the curve statisticallyadjusted by Smith River but is in reason with the apparent shift indicated by the Eel River at Scotia, 1911-60 shift from the 1932-60 curve. Frequency curves are plotted on Plate A-9 for the Smith River near Crescent City, Eel River at Scotia, and Redwood Creek at Orick. Annual maximum discharges for Redwood Creek at Orick and Smith River near Crescent City are tabulated in Table A-4. The adopted discharge-frequencycurve is used in determina- tion of the economic evaluations of the proposed project (see Plate D-1 in Appendix D).

A-17. RAINFALLDEPT~-DI~ATION-FEEQUENCY ANALYSIS

The rainfall depth-duration-frequencycu~es plotted on Plate A-10 were derived by procedures outlined in Technical Paper No. 28, "Rainfall Intensitiesfor Local Drainage Design in Western United States", U. S. Departmentof Commerce,Weather Bureau, Washington,D.C., November 1956. Values taken from these curves were used in the study for interior runoff and drainage from areas behind the leveed reaches of the proposed plan of improvement.

SECTION Vll - INTERIOR DRAINAGE

A-18. PROBLEM AREA

Drainage facilities must be provided for surface runoff from the area adjacent to the proposed levees. There are three general areas to be considered: (1) 884 acres adjacent to the right bank levee downstream from the town of 0rick~ (2) 281 acres adjacent to the right bank levee at and upstream from the town of Orick~ and (3) 2,230 acres adjacent to the left bank levee and extending the entire length of the project. These P areas consist of about 60 to 65 percent of steep hillside rising to ele- E vations of 800 to 1,200 feet above mean sea level° Areas (1) and (3) S adequate natural drainage to the lower end of the project. Area (2) C A cut off from the lower end of the project by a natural ridge. With open- D end levee design as proposed in the plan of improvemen% no water will be E R trapped behind the levee in areas (1) and (3)o 0 A-19. DESIGNCRITERIA 3 B 6 Runoff hydrographswere estimated for Area (2)~ based on storms con- 3 sistent with criteria set forth in the Preliminary Manuscript of an Engineer ~nual "In+~rior Drainage of Leveed Urban Areas." The criteria for an urban commercialarea are~as T611ows~

"Insofar as practicable~gravity outlets should be provided to discharge runoff from 100-year frequency (i.eo, 1 in lO0 years) all-season rainfall without interior ponding exceediug acceptable ~ levels; storm- water pumping stations if provided~ should have a capacity at least adequate to dischargerunoff from rainfall having an average frequency of once in tp 30-years,coincident with the design flood stage in the main river ......

A 100-year storm of six hours duration was selected from the appropriate curve presented in Plate A-9o Total storm depth is 5.00 inches with run- off estimated to be 3.76 inches. A 15-minute unit hydrograph was derived syntheticallyand a peak discharge of 440 c.f.So computed for the 281-acre contributing area. For the alternate criteria of a 30-year storm coincident with the design flood in Redwood Creek, a rainfall depth of 6.60 inches was selected for a duration of 24 hours. This duration was based on the estima- ted period of gate closure of the gravity outlets. The 24-hour rainfall follows the standard project storm distribution°The storm depth was extra- polated and duration extended to seventy-twohours by ratio of the maximum 24-hour depth to the total depth of the standard project storm, to give a total storm depth of 8°4 inches over the interior area during the occurrence of the standard project flood° Interior runoff was estimated to be 5.1 inches and an inflow hydrograph computed. The computed hydrograph has a peak discharge of 143 c.f.So which occurs prior to the time of gate closure. Details of pump and/or ponding requirementsare presented in Appendix C, "Bases for Design and C~st Estimates~"

A-9 APPENDIX A TABLE A-I PRECIPITATIONSTATIONS IN OR NEAR REDW00DCREEK BASI~ Survey Report Redwood Creek, Humboldt P Count~. Calif. E Normal Lat. and Long° Super- Period Elev. annual t~ m.s.l, precip. ~/ A Station name i/ in degrees and vising of D minutes agency record (ft.) (inches) E R O Blue Lake (Guest) 40-53.8 123-59.2 Private 1951-* 125 45.8 Private 1953-* 750 - 3 Blue Lake (Pon Ranch) 40-57.7 123-50~i 5 Blue Lake (Preston 6 Private 1952-*~ 1,850 70.7 5 Ranch) 40-56.4 123-52~6 Blue Lake (Redwood Creek) 40-55 123-49 USWB 1956-* 975 - Burnt Ranch (Ambrose) 40-50~2 123-32,7 Private 1953-* 2,200 42.1 Burnt Ranch, Camp 36 40-48~3 123-28~7 CSDH 1942-* 1,475 32.9 Burnt Ranch [Kaut) 40-47~7 123-28~7 Private 1946-* 2,250 33.7 ~WB China Flat, A 40-52.5 123-35~2 US 1909-37 600 - China Flat, B 40-5L8 123-34~7 USWB 1931-55 600 46.0 Crannell (Demo) 41-01~8 124-06.7 Private 1949-* 20 49.4 Crannell Camp 41-00.6 124-04~ 8 Private 1933-48 40 52.6 Eureka, B 40-48.1 124-O9® 8 USWB 1887-* 65 36.8 Hoopa, B 41-02.9 123-40®6 USIS 1940-42 359 - Hoopa, C 41-02.9 123-40.6 USWB 1941-* 350 48.7 Hoopa, 2 SE 41-02 123-39 USWB 1954-* 315 - Hyampom 40-37.0 123-27® 2 USWB 1913-* 1,240 39.1 Kneeland, l0 SSE 40-38 123-54 USWB 1954-* 2,356 Korbel (Morrison) 40-52.2 123-57o5 Private 1937-* 120 57.1 Orick ~rcata- Redwood) 41-19.3 124-02.6 Private 1955-* 40 - Orick (Davidson) 41-19.4 124-02.5 Private 1950-* 60 67.7 Orick (Dutton) 41-12.8 124-06.0 Private 1951-* 500 79.3 Orick, Prairie Creek Park 41-21.9 124-01°2 USWB 1937-* 152 70.9 Orleans, B and C 41-182 123-32.4 USWB 1903-* 410 48.5 Orleans (Gephart) 41-14o4 123-39.4 Private 1938-* 420 63.3 Patricks Point State Park 41-08o2 124-09~2 CSDP 1947-* 225 54.8 Salyer Ranger Station 40-54~0 123-35~3 USWB 1928-* 600 45.0 Trinidad Big Lagoon Camp 41-09.8 124-06~i Private 1947-* 50 49.8 Trinidad Head, L.H° 41-03ol 124-09~0 USCG 1891-43 198 42.5 Weitchpec, A 41-17.6 123~40~9 USWB 1910-17 1,700 77.0

LEGEND: - USWB.- U. S. Weather Bureau CSDH - California Division of Highways USIS - U. S. Indian Service CSDP - California State Division of Parks and Beaches USGC -United States Coast Guard NOTE

2~SeeAdjusted Plate to3 for 1907-56 location base withperiod° respect to basin. TABLE A-I APPENDIXA "TABLEA-2 SurveyReport -RedwoodCity, Humboldt County, California Ori0k Orisk Station ¯ ureka -China Flat "Hoopa ~rairieCreek "Kneeland31ue Lake 31ue Lake near "Weitchpec Orleans "Hya~pom i0 S~ (Preston) (Guest) "(Dut%o,) Obs. Time Mid.lght5 p.=. Mi~ight 4 p.m. stor~ MidnIzh% 5 p.m. 7t30 p.m. 6 a.m. p.m. ~ p.m. p.m. Mar. 17 3.36 1907 18 1.00 19 1.62 20 .28 21 .74 22 1.41 23 .65 24 .77 25 .53 26 10.72 Nov. 18 .66 1926 19 1.31 20 .12 21 .05 22 .44 23 .78 24 .59 25 .73 Monthly Monthly 26 .35 total total 27 .75 only only 28 .42 available 2g avail- 4.05 able 30 1.09 Dec. i .40 1926 2 2.49 14.23 Est. 19.0 Eat. 21.0 Jan. 30 .41 ;80 .78 .19 .68 1915 31 .99 .79 1.00 2.61 2.02 Feb. i 4.45 7.11 5.00 2.88 6.25 1915 2 1.07 1.65 2.36 1.14 3.34 3 .~6 7.40 10.94 11.03 7.28 13.35 Dee. 7 .01 .43 .05 1939 8 2.41 1.87 2.62 9 1.09 3.23 2.63 I0 3.77 1.70 3.05 ii ___9_ -61 7.28 7.84 8.62 Dee. 17 1.44 1.19 .64 3.08 1940 18 .27 2.66 1.74 1.38 19 .01 .04 .Ii .ii 2O 1.32 2.86 2.30 2.61 21 .23 1.38 .72 1.47 22 .05 .09 .68 .15 23 1.33 .99 .73 1.25 24 1.54 2.55 3.24 2.6L 25 .71 .31 .37 1.25 26 1.55 2.62 2.16 1.63 27 8.45 15.57 13.80 16.52 Jan. 20 1.61 3.70 2.08 1943 21 .73 2.81 1.95 22 .53 1.07 .94 23 2.91 8.41 5.43 0ct. 25 .84 .06 1.33 1.33 .45 1950 26 .76 .99 2.11 .65 1.99 27 1.58 .94 3.~ 1.48 2.28 28 1.90 2.25 3.68 4.69 3.45 29 5.04 3.15 I.~ 11.50 2.33 30 __J.l _2~ 10.33 10.02 12.38 21.05 i0.70 Dee. 4 2.41 .65 2.34 1.49 3.08 2.63 .21 1952 5 .76 2.46 1.12 i.56 1.33 .63 3.14 6 2.73 2.36 3.68 1.81 3.06 1.38 .95 7 .37 2.25 2.13 .29 .75 .13 2.22 8 .25 .47 .48 .56 .47 .25 .57 9 .21 .68 .86 .28 .46 1.25 .39 i0 .99 iJm 7.72 9.74 11.66 7.53 10.65 6.40 7.88 Jan.° 16 .92 1.21 1.42 2.00 1.60 1.81 .30 1.22 1953 17 3.70 3.32 5.01 4.88 6.90 4.88 2.88 4.20 18 1.84 3.83 2.47 5.19 7.53 1.75 6.45 3.57 19 .38 .50 .90 1.00 1.07 .68 1.91 1.22 20 ___Q 7.35 9.84 10.76 14.60 18.35 9.12 13.94 11.54 Dee, 17 1.58 .41 1.93 2.10 .07 .88 1955 18 .81 2.36 1.90 .72 I.~ 1.52 19 .90 1.39 1.90 1.28 2.50 1.95 2O .41 .36 1.25 .78 .70 .96 21 .96 1.82 5.46 4.95 .98 3.05 22 1.38 1.63 2.11 5.57 3.98 3.50 23 1.20 9.62 15.11 16.60 11.88 12.85 TABLE A-2 APPERDIX A TABLE A~3 . p STREAM-GAGING.STATIONS E Survey Report RedwoodCreek, HumboldtCOo ~ Calif A D E R - ’ 0 ..... Drain- - age Period Lato & LOtto Super- Extremes 3 Station Area of in degrees vising 5 Agency Diachar~e DLte, 6 (S~ mi) Record ,,& Minutes~.~ 7 RedwoodCr. 1911-i ~/ 1%7oo. / ,L17/. @ Orick~ 278 1955~J ,~1=17o5 12~-05o~ USGS 5o,ooo. 12/.22/.55 1949-5~/ " " C ore so,oooi/ls/ss

Redwood.Cr. nr Kor~el~ 82°8 1911-13 &0-57o5 125-50o6 USGS 7,412~/ 2/17/12

Redwood Cry, r~ Blue Lake~ 67°5 1955~/ ~0-5~o3 lZ5®~8.9 USGS 12,100 18/21/55

LEGEND

USGS - U. So Geological Survey C of E - Corps of Engineers ,~ Water stage recorder - Mean daily, instantaneousvalue not available ~ Station in operation ~ZStaff readings of maximum stages during flood periods

TABLE A-5 APPENDIX A ~___~MAXIMUMDISCHARGE Redwood Creek at Orick and Smith River near Crescent City

S e Re rt Redwood Creek, Humboldt County. Calif, 1~ater Redwood ear Smith RiverCreek Date 1932 6i~vO0 !933 51~500 1934 33~i00 1935 33~900 1936 55~500 1937 70~i00 1938 78~900 1939 51~000 !940 37~200 1941 46~000 1942 62~400 1943 91~ 400 1944 40~ 600 1945 56~ 500 1946 123~ooo 1947 50~000 1948 83~I00 30~000 i/ 7 January 1949 64,300 No data~vailable 1950 91,400 37,000 18 January 1951 152~000 28,000 2/ 17 January 1952 61~500 13~500 ~ 1 Eebruary 1953 139~000 50,000~J 18 Jannary 1954 141,000 27,200 24 November 1955 70,200 28,100 31 December 1956 165~000 50,000 22 December 1957 67~i00 24,100 12 March 1958 94,300 22,200 13 November 1959 90~400 17,500 12 January 1960 74,300 25,000 8 February 4 o 99 4 o 46 12-year mean log discharge. o85 4°43 29-year mean log discharge. 00149 0~155 12-year standard derivation~ 0 o 190 0 o 163~/ 29-year standardderivation. 0°24 ~ coefficientof determination. 0.5 - coefficient of correlation.

!/From high~ater marks° 2/From Corps of Engineers staff observationand rating curve developedafter 1953o ~/ Adjusted to Smith River°

TABLE A-4 TABLE A-5 UNIT HYDROGRAPH DATA Survey Report Redwood~ Greek, ~;:c~:’, ~. Humboldt~Oo~4ty<,<.0alif. 2-hour 2~hour P Orick Prairie Creek ~t mouth E Re~wood Creek at 0 0 0 A 2 94O 80O D 4 2,200 3,100 E 2,500 R 6 4,400 O 8 6,990 i, 600 i0 9~ 870 i, i00 3 5 12 8,070 9OO 6 14 6,800 7OO 9 16 5,710 55O 18 4, 800 45O 20 4,030~: 35O 22 3,390 270 24 3,020 2OO 26 2,690 150 28 2,400 I00 30 2; 210 7O 32 2,030 4O 34 1,870 2O 36 1,720 0 38 I, 580 40 1,450 Basin Data 42 1,340 Redwood Prairie 44 1,230 Creek Creek 46 I, 130 48 I, 040 Basin Area (square 50 960 miles) 278 40 52 88O Stream Length (mi.) 61 12 54 810 Length to Center of 56 75O area (~i.) 25 4 58 690 Slope (ft./mi.) 79 67 60 ~630 Lag time (hrs.) 16 6 62 580 Normal Annual Pre- 64 530 cipitation(in.) 78 75 66 490 68 440 7O 4OO 72 350 74 3OO 76 260 78 220 8O 180 82 14o 84 1oo 86 60 88 2O 9O 0 TABLE A-5 U.S. ARMY

1"i.f’~ \ \ VALLEY\\ \\ \\ \ RESERVATION\

~.o..._~o.

LEGEND ~). Preclgitatlon5tat~ StreamGogir~g ~tollgnt

U.SHigh~ays

,~,,,Rl~tf M{~e4

EUREKA FLOODSURVEYCONTROL~EPORT \. REDWOODCREEK \ HUMBOLDTCOUNTY, CALIFORNIA \ GENERALHYDROLO6YMAPOFBASIN e o = 4 U.S.ARMY~N(O~HEET$ ENGINEERDISTRIC’Ir, SANFRANCISCO,GORP$ OFENGLNEERS, SHEE’fJLII.YNO.1961I PLATEA-I ;ORPS OF ENGINEERS U.S. ARMY

6000

P E S m 5400 MAX IIMUM C A D E 5 000 R 0 3 5 7 3 4000

3000 f-REDWOOD CR. ot ,ORCl(

2000 Z

Z fPRAIRIE CR. ot MOUTH 0 m k- ,I000 _J LLJ

0 20 40 60 80 I00

PERCENT OF BASIN ABOVE GIVEN ELEVATION

FLOOD CONTROL SURVEY REPORT REDWOOD CREEK HUMBOLDT GO., CALIFORNIA HYDROLOGY AREA-ELEVATION CURVES

IN I0 SHEETS SHEETNO.. 2 U.S. ARMY ENGINEER DIST,. SAN FRANCISCO, C OF Ir DRAWN: D,R.B. FILE NO. TRACED: S.L. TO ACCOMPANYREPORT CHECKED:W.R.T.DATED: MUG. mGI 85-46-1 PLATE A-2 CORPS OF ENGINEERS U.S. ARMY

9 S SCALEIN MILES E CR, PARK P \\ E ( DAVIDSON) S ORLEANS C 77.0 48,5 A tL WEITCHPEC D E 41Ol5’ # 4~I°l 5._.~ R J-I-ORLEA INS I -=,, 0 ~..~’~u’~’"(G /EP }HART) 3 5 (DUTTON) 7 5 ,°/ CAMP 7o 54,8 PATRICKS POINT PARK ,.--’@

IINIDAD ~48)Z HO0PA 4EAD ( , LCRANNELL(DEMO) ~ , HOOPA Z SE ’. 41000 52.6 ~ + 4t°00 + ICRANHEL LT\

LAKE RCH.)

45.BBLUE LAKE (GUEST) 45"OsALYERRANGER STATION 57.1 KORBEL 46.0 (MORRISON) CHINA FLAT 42.1 BURNTRANCH(AMBROSE) 32.9 BURNTRANCH W’36 3~.7 BURNTRANCH (KAUT) 4_’ 0°45 + 40°45_~~

iS ~KNEELAND~ IO SSE ~L HYAMPOM / LEGEND DRAINAGEBASIN BOUNDARY. FLOODCONTROL ~’~"~80~..,,.iSOHYETS (BASED ON 50 YEARPERIOD 1907-56.) SURVEY RE PORT REDWOOD CREEK RECORDING RAIN GAGE. HUMBOLDTCO.~ CALIFORNIA HY DR0 LOGY 45.8 NON RECORDINGRAiN GAGE WiTH NORMALANNUAL RAINFALL DEPTH EXPRESSEDIN INCHES AND TENTHS. NORMAL ANNUAL ,,--, DAMSITE PRECIPITATION "~ WATER STAGE RECORDER IN IOSHEETS SHEETNC’. 3 I REDWOODCREEK AT ORICK. ~.1 S. ARMYENGIr~EER D!ST, SANFRANCISCO, C OF E REDWOOD CREEK NEAR KORBEL. DRAWN:D.R.B. FILENO 2 TE’ACEO"S.L. TOACCOMPANY REPORT 3 REDWO00 GREEK NEAR BLUE LAKE. [’hECKED:W.R.T. DATED:AUB. IR61 8,5-46-1 PLATE A-3 " .... - ...... r ...... CORPSOF ENGINEERS , U.$.ARMY I I t i I I I 2 I

18.35"BLUE LAKE ~PRESTON) s-" # ÷ 17.43"BLUE LAKE{PON RANCH) ¢.d .... ° 4. ¢ ¢1 Ii + II 14.60"DRIGK-- PRAIRIECR. PARK TRINIDAD-SPRUCECOVEt3,~. / 10,76 I/ GRANNELL(DEMO)I, HOOPA I 41ooo____~’ CRANNELL+ (CAMP} .6~’ Jr 4I<’00------’ ! ~ / / 0 II. 54"ORLEANS BLUELAKE(PON RANCH) II # 10.76"HOOPA,R ECORDER BLUELAKE (PRESTON) I 4/ o II ¢ 9.84"CHINA FLAT

9./2 /*"i’/s \ BLUELAKE(GUEST) 8.24SALYERR.S. // 7.$fl" EUREKA, RECORDER III~3 9.84CHINAFLAT ~,/X / i 0//j~ /I/ ~ / EUREKA i~t I /’T. / ÷ ,’,jP’f It 16 17I 18I 19 2OI \U KNEELAND10S~E JANUARY1955 MASSRAINFALL CURVES

FLOODCONTROL ISOHYETALMAP REDWOODSURVEYREPORTCREEK HUMBOLDTHYDROLOGYCO.~CALIFORNIA $ 16-20 JAN. 0 1953 MASSCURVES SCALEINMILES ANDISOHYETAL MAP 16-20 JANUARY1953SHEETNO.4’ u..~..!NolOSHEETS/~r~My ENGINEER DIS[r~AN FRANCISCO, FILE"CO! l~OE Oe~W,~D.R.B. ACCOMPANY ITRACED,S.L.CHECKED:W.R.T. TODATED:AUg. ~EPORT,BeD 85-46-1 PLATEA-4 CORPSOFENGINEERS U.S.ARMY i J I 1¸ I I I 1 I I i I ] ORICK-PRAIRIECR.PARK / ¯ ,_--0 6.60"BLUELAKE (PRESTON} ,’~ 15.11"KNEELAND 7SSE - RECORDER I ¯ ., J, ~’~ -- 13.BO"HYAMPOMRECORDER It.85 ORLEANS // ~ . ..--~" / ’t’, 41015’ ~, t2.64 R.$. ~ D II.BB’O Q’Z~, . .f "X-9.6~"ORICK-PRAIRIECR.PARK

’ I ¯ / + 7.62"CRANNELL(OEMO] / ’ *:_2.J _ ~ ~- ..... 6.45"EUREKARECORDER

_17 18 19I ZO 211 22 SALYERR.S...... DEI~,EMBER 1955 BURNT\RANCH No36 i0,~610,30 MASSRAINFALL CURVES BURNTRANCH EUREKA (KAUT) ~ 40e4~ ~4004’ S_.~

\b IS,II \ KNEELANO~ Lt HYAMPOM/3,80 g SURVEYFLC’3DCONTROLREPORT REDWOODCREEK ISOHYETALMAP HUMBOLDTHYDROLOGYCO..CALtFORNIA 17-23DECEMBER1955 5 o 5 MASSCURVES ANDISOHYETALDECEMBER t955MAP SCALEIN MILES 17-23 SHEETNO,5 INI0 SHEETS DiSTSANFRANCISCO,~ OfE DRAWN,3.S.ARMY D.R.B.ENGtNEFR FiLENO. CHECK".~W.R.T.TPACEO:S,L.~0OARED:ACCOMPANY AUeREPORTl~e~85-46-1 PLATEA,-5 COR~OFENaI~EP.RS- U.S.ARMY

RAINFALLDISTRIBUTATIONBYKNEELAND I0SSE I i I I0 ~..._.-~,90ToRED*OODC.F.S. GR. ATORICK f I ..... t I t BASIN8lUNIT HYOROGRAPHDATA I I I REDWOODCR.PRAIRIE CR. RUNOFF J AREA 270Sq.ml. 40Sq.mi. RAINFALL-RUNOFFDATA 8 LEN~ITHOFWATER COURSE 61.2miI2.Oml I REDWOODCR. PRAIRIE GR. LENGTHTOCENTER 25.3ml4.3mi 72-HR.RAINFALL 12.5iM. 6.5i~.’u’ ~zOVERALLSLOPE 79.2fVrnl66.6ft/ml LOSS 4.74tN. 3.31N.t LLco/S 174 B.4 I SURFACERUNOFF 7.7IN. 3.21N,K- LAG(TIME AT50% ULTIMATE) 16hrs. 6hrs. i ’ MIN.LOSS RATE .CIN/HR. .OBI~/HR.t NORMALANNUALPRECIP. 78in. 75in. I 1 I BASEFLOW 500G.F.S. BOOC.F.S.e 6d I 1 I J eESTIMATED VALVES=, 0 I t UNCAGEDAREA o t I z ,.I ~’°°°°I¢,F.S.I " °"’4 I <~ .31ooc..$.! O PRAIRIIrtGR.ATM )UTH I J ~.o.,OOCR.6A(3EO I I I \ I r/ [ 24TIMEIN48 HOURS72 96 I I 2-HOURUNIT HYDROGRAPHS I ., I .C..io.,,,,olIo. I I 1 ~,~L\ ESTIMATEO [ I : I , 1 \~J,~NATURA"R/C,,’SS,ON

FLOODCONTROL REOWOOOSURVEYREPORT CREEK ’ I I HUMBOLDTHYDROLOIYCO..CALIFOR~’IA ....."~-’r23..... 424 25 HYDROLOGICDATAANDUNIT HYDROGRAPH20-25 DECEMBERDERIVATION~1,55 DECEMBER1955 SHEETNO.¯ U.S.INI0 ARMYSHEETS ENGINEER DIST.,SANFRANCISCO,~ OFE UNITHYDROGRAPH DERIVATION [;F,AWN: D.R.B. FILENO. CHECKE~,W.e.’r.~RACED:3.L. OATEO:TOACCOMPANY AU~.iS61REPORT85-46-1 =t .... PLATEA-6 I U.$,ARMY F- [I 41i 3"~ AVERAGERAINFALLOFDISTRIBUTIONKNEELAND IOSSEBY U ANDKLAMATH RECORDERS. I -l_ J I SURFACERUNOFF-- I I I I I r2~ , I 3O I I I ’ jf~%~Z8,100 C.F.$. GAGED s REDWOODCR.AT ORICK ,,r r DO c.,.,.,,,o, FFDATA I I/ ~ II RAINFALL-REDWOODRUNOCR. PRAIRIE CR. I I/ ~ AREA 278=o,. mi. 40sq.mi. ~’!1 ~~ I TOTALRAINFALL 7.20Inches TOTALLOSS 3.08inches rr ~\ I MJN.LOSSRATE 0.05in/hr. / ’~ BASEFLOW I. 05inches 2O ,,.I TOTALRUNOFF 5.17inches l~

40°4’5’ 40o4~

.¢.._~e250C.F.$. I STIMATED ~ ~’~ ¯ ’. PRAIRIEC~. AT MOUTH ’ I "~ ¢,.,, .EELA,D SSEJt~ < ;!IISOHYETALMAP STORMOF29DECEMBER1954-I JANUARY1955 SURVEYFLOODCONTROl.REPORT REDWOODCREEK ._.______-J-~- _’--~-- ~-- I HUMBOLDTCO., CALIFORN|A -~-~~"I--.--30DEC.- 31iDEC." ...... I~ JAN...... 2JAN. HYDROLOGICHYDROLOOYDATA 29DECEMBER 1954-2JANUARY 1955 ~jN.~OSHEETS SHEETNO.7 DISCHARGEHYDROGRAPH- REDWOODCR.otORICK DRA#N:.. ARM~D.R.I.ENGINEER DIST.,SAN FRANCISCO, FILECOF NO.E 30DECEMBER-,. 1954-2JANUARY 1955 TOACCOMPANY REPORT UNITHYDROGRAPH CORROBORATION CHECKED.if.TRACED:S.L. R-T. DATED AUG. lttll 85-46-1 i . - i i i J PLATEA-7 ...... i U.$. AR MY

RAINFALL-RUNOFF DATA I REDWOODCR. PRAIRIE CR. i i | AREA 278 sq.m|.40=q.mi. TOTALRAINFALL I 7.8inches18.0inches TOTALSNOWMELT .4 inchesO inches iI~,L,~ " I i...... TOTALLOSS 3.26inches3.22inches .-I ...... MIN.LOSS RATE .08in/hr...08in/hf. BASEFLOW 5000c.f.s.700¢.f.$. l, . LJ- II Ji sU,FA.RUNOFF J I LEGEND I ~ZO~,,,~ISOPERCENTUAL LINES il f ---- ADAPTEDLIMITS OF TRARSPOTION I i . e~- rl RECORDINSPRECIPITATION STATIONSUSEDTO DISTRIBUTE TOTAL ~.’ i ] STORMPRECl PITATION 80 ..... I I , I /~--J~-77,000C.F.$. +lO SCALEIN _~MILES I / \1 REDWOODCREEKof ORICK illlrl ,,-v;60 d 0 0 IO,OOO -40 AREAIN SQUAREMILE¯ Z I1 AREA-DEPTH CURVE (9 1 ~20~ I 16,000I..-i \IC.f.S...... ! RAIRIECREEK I atMOU iI ISOPERCENTUALLINES I I STORMOF21-23 DEC. 1955 I "------4-i " f ~. - I iI I TOTALSTORMPRECIPITATION IN FLOODCONTROL 21 22" 23 24 25 26 PERCENTOFNORMAL ANNUAL PRECEPITATiON REDWOODSURVEYREPORT CREEK HUMBOLDTCO.,CALl FORNIA STANDARDPROJECTFLOODHYDROGRAPHS HYDROLOGICHYDROLOSYDATA STANDARDPROJECTSTORM-FLOOD TRANSPOSEDGENERALSTORM 21-23 DEC, 1955 IN10 SHEET~ SHEETNO. ¯ DRAWN:U.S.ARMY D.R.B,ENGINEER DIST,SAN FRANCISCO, FILECOF E TRACED:S.L. TOACCOMPANY REPORT CHECKED:W.R.T,DATEDAUe.=S=~ ~5-46-1 PLATEA-8 CORPS OF ENGINEERS U.S. ARMY

EXCEEDENCE INTERVAL IN YEARS 2 5 I0 20 50 I00

9O0 SO0 P 700 E S 600 f C J_/ A 50O :’k"1f D EEL RIVER d E ot SCOTIA R 400 0 3 5 8 el 7 SM ITH RIV f -/,// nr. CR:.SCENT CIT’ / 9 r Y / ® 0 qje" < ® 0 / 0 J J / d J I00 J j ® ® X 90 Z 80 / x p,- 70 REDW~POD CR. f ot ORICK LIJ 60 / / 50 <~ ’1- (.~ 40 .> >"~---ADCPTED CURVE X 0 J 3O G

f SHORT TERM o/ / 194e--60 2O f L ESS 1940 o/ J f

I0 2 I .5 90 80 70 60 50 40 30 20 I0 5 EXCEEDENCE FREQUENCY PER I00 YEARS

FLOOD CONTROL SURVEY REPORT REDWOOD CREEK HUMBOLDT CO., ~ALIFORNIA H YDROLOeY DISCHARGE-FREQUENCYCURVES

IN IO SHEETS SHEET NO. 9 U.S.. ARMY ENGINEER DIST., SAN FRANCISCO, G OF E DRAWN: D.R.L FILF NO TRACED:II.L. TOACCOMPANY REPORT O~,,l’~, == a~...,1 CHECKED:W, R.T. DATED: AUQ. 1961 P E S C A D E R 0 10,(3 I I I I I I I I I I" __ 8.0 3 - 50 yr.- 5 - 30 yr. 8 e.o 9 ,o,, 5.0 ~ yr:- _/~- .~ ~,~. 2yr:-

z_ -

.6

.4

DURATION IN HOURS

REFERENCEU.S.W;B. T.P. NO. 28

FLOODCO~I~TR OL SURVEY REPORT REDWOOD CREEK HUMBOLDT CO., CALiFORNiA HYDROLOGY RAIN FAL L- DE PTH - DURATION FREQUENCY CURVES IN I0 SHEE’rS SHEETNO. I0 U.S. ARMY ENGINEER DIST.. SAN FRANCISCO. (; OF DIIAWN: D.R.B. IRI, E NO. TRACED: Y.~.Q. TO ACCOMPANY ~EPORT .... CNECKED:W.R.T.DATED: AUe. t~l 8~-46-1 PLATE A- I0

APPENDIX B GEOLOGY, SOILS, AND SOURCES OF CONSTRUCTION MATERIALS

P TABLE OF CONTENTS Es Paragraph Subject A D TOPOGRAPHY AND GEOLOGY B-I E B-1. R B-2. FIELD EXPLORATION B-I B-I O B-3. LABORATORY TESTING B-4. SUBSURFACE CONDITIONS B-I 3 B-2 5 B-5. GROUND WATER 9 DESIGN VALUES B-2 3 B-6. B-7. STABILITY OF SLOPES B-3 B-8. SLOPE PROTECTION B-4 B-9. TOE DRAIN B-5 B-IO. TYPICAL LEVEEAND CHANNEL SECTIONS B-5 B-If. SOURCES OF CONSTRUCTIONMATERIALS B-6 a. Riprap B-6 b. Embankment Materials B-6 c. Filter Material B-6

LIST O~ TABLE AND PLATES Table and Plates i Title Table B-I Summary of Soil Test Plate B-I Location of ExplorationHoles Plate B-2 Logs of ExplorationHoles Plate B-3 Logs of ExplorationHoles Plate B-4 StabilityAnalysis Plate B-5 StabilityAnalysis Plate B-6 StabilityAnalysis Plate B-7 StabilityAnalysis Plate B-8 Filter Material Plate B-9 Typical Materials Plate B-lO Triaxial CompressionTest Plate B-11 Typical Levee Sections APPENDIX B GEOLOGY~ SOILS~ AND SOURCES OF CONSTRUCTIONMATERIALS

P B-1. TOPOGRAPHY AND GEOLOGY E S C Redwood Creek heads in the mountains about 20 miles east of A Eureka, flows north-northwesterlyfor 50 miles through a narrow, D E V-shaped gorge to a location about 2 miles upstream from Orick. Here R the creek turns generally westerly, flows through a wide alluviated 0 valley and enters the ocean about 2 miles downstream from 0rick. The 3 upstream 40 miles of the creek essentiallyis along a fault contact 5 between the Kerr Ranch schist on the west and Franciscan Group sediments 9 5 on the east. However, the downstream l0 miles of the canyon iscut entirely in Kerr Ranch schist and schist apparently underlies the alluviated valley. The alluviated valley ranges from 700 to 1500 feet in width and the alluvium is deeper than any of the subsurface exploration. The Kerr Ranch schist is a product of low-grade metamorphism,is hard, with alternating bands of light and dark colored minerals, and generally breaks into 2-foot sized blocks rather than into slab-shaped pieces. Outcrops usually show relatively unweathered schist.

B-2. FIELD EZPLORATION

Field explorationwas conducted during the period, August 1956, October 1958, and March 1960. Twenty-one hand or Power auger holes ranging in depth from 3 to 25 feet were drilled along the banks of Redwood Creek. All holes were drilled to a depth of 25 feet or to a depth of 5 feet into gravelly material unless caving prevented drilling to the required depth. Disturbed samples of the various soils encountered in the auger holes were taken for identificationand classification. Borrow investigationfor the pervious materials consisted of obtaining samples of streambed sand and gravel. Samples were obtained from two locations by a dragline. The locations of the exploration holes are shown on Plate B-1 and the logs are shown on Plates B-2 and B-3.

B-3. LABORATORYTESTING

Laboratory testing consisted of mechanical analyses and Atterberg Limits tests made on selected samples to verify the field visual classificationof the materials encounteredin the explorationholes. Soil classificationsare shown on the logs of explorationholes on Plates B-2 and B-3 and the test results are shown on Table B-1. A consolidated-drainedtriaxial shear test was made on a representative sample of streambed sand and gravel. The results of the triaxial shear test are shown on Plate B-9.

B-4. SUBSURFACECONDITIONS

Field exploration indicates that the subsurfacematerialsare predominatelyfine silty sand and sandy silt with some clays overlying sands and gravels. The depth of sands and gravels has not been determined.

B-1 In the right bank, the fine grained material is approximately8feet in depth between Station 165~60 (upstream end of levee) and Station 140100, approximately5 feet in depth between Station 140100 and Station 90~00, and from 16 to more than 25 feet in depth downstream of Station 90#00. In the left bank, except between Station 123~00 and Station ll0~O0, the fine grained material is more than lO feet in depth. Between Station 123~00 and Station llOiO0, approximately5 feet of fine grained materialsoverlie the sand and gravel.

B-5. GROUNDWATER

Stabilized groundwater table was not established as the explora- tion holes were backfilled immediatelyupon completion of the drilling. During exploration,ground water was encountered in the explorationholes from 6 to 12 feet below the existing ground surface. Materials were saturated to the ground surface at most locations as a result of heavy rains just prior to and during explorations. Due to the pervious zone of sand and gravel in the foundation, groundwater encountered in the explorationholes drilled near the creek channel reflected the water level in the channel. Water level readings made during explorationsare shown on the logs of explorationholes on Plates B-2 and B-3.

B-6. DESIGN VALUES

Based on laboratory tests, field descriptionand experience with similar soils, the following design values are adopted for the various materials.

Foundation(Undisturbed)

(1) Overburden - Silty Sand~ Sandy Silt~ Sandy Clays

Dry Weight ...... 90 lbs. per cu. ft.

Moist Weight - 104 lbs. per cu. ft.

SaturatedWeight ll9 lbs. per cu. ft.

Buoyed Weight 57 Ibs. per cu. ft.

25 degrees

Gravelly Material~ Sand and Gravel Dry Weight 120 ibs. per cu. ft.

Moist Weight ...... 126 ibs. per cu. ft.

Saturated Weight ...... 137 lbs. per cu. ft. Buoyed Weight ...... 75 ibs. per cu. ft. 31 degrees

B-2 b. ~mbankment Materials

(i) ImperviousFiil from OverburdenSoil.s P E lOO lbs. per cu. ft. S Dry Weight ...... - ...... C A Moist Weight ...... 115 lbs. per cu. ft. D E R Saturated Weight .... 126 lbs. per cu. ft. O 3 Buoyed Weight .... 63 lbs. per cu. ft. 5 9 26 degrees 7

(2) StreambedSand and Gravel

Dry Weight ..... 120 ibs. per cu. ft.

Moist Weight 126 lbs. per cu. ft.

SaturatedWeight 137 lbs. per cu. ft.

Buoyed Weight --° 75 ibs. per cu. ft...... 31 degrees

B-7. STABILITYOF SLOPES

a. Channelside. The levee and channel slopes are to be i vertical to 3 horizontal. The stability of the channelsideslope was analyzed by the circular arc method. As the foundation consists of materials with varying strength, the analyses were made for the most critical foundation as represented by the depth of fine grained overburden material extending to the full depth of the channel bank. The following conditions were analyzed:

(I) ~ Forces. Stability analysis for gravity forces wlthwater surface at half slope height is shown on Plate B-4. A most critical safety factor of 1.24 was determined for a 1 vertical to 3.O horizontal slope.

(2] Gravity and qol~__~rthquakeForces° Stability amalysis for gravity plus O.lg earthquake forces is shown on Plate B-5. Since the probability of high water and earthquake occurring simultaneouslyis very remote, normal flow condition of approxi- mately 2 feet depth of water in the channel was used for this analysis. A most critical factor of safety of lol0 ~s determined for the 1 vertical to 3.0 horizontalslope°

B-3 (3) Sudden Drawdown. Except for the impervious central core, the levee will be constructedof pervious materials and sudden drawdowa seepage force will not develop in the embankment. Since the relatively impervious foundation materials are underlain by pervious sands and gravels, seepage forces in the fine grained foundation materials would be essentiallydownward and would not influence the stability of the slope. In view of the above conditions,stability analysis for this condition was not made.

b. Laudside.

Due to the impervious central core of the levee and the short flood duration, steady seepage through the levee would not be developed and analysis was not made for this condition.

As explorationindicated that the foundation materials to the ground surface in most locations were saturated, stability analyses were made for the landside slope of the levee with the water at the ground surface.

(1) Gravity Forces.

Stability analysis for the gravity force was made by the circular arc method and is shown on Plate B-6. A most critical factor of safety of 1.28 was determined for a 1 vertical to 2.5 horizontal levee slope.

(2) Gravityand O. lg EarthquakeForces.

To the most critical arc determined for the gravity forces, an earthquake force of O.lg was added for this stability analysis. A safety factor of 1.O0 was obtained for the 1 vertical to 2.5 horizontal slope. Stability analysis is shown on Plate B-7.

B-8. SLOPE PROTECTION

Except at the highway bridge and near the downstream end of the levees, the average channel velocity is 12 feet per second. Through the highwaybridge section the average velocity is 12.7 per second and near the downstream end of the levees, the average velocity gradually increases from 12.0 feet per second at Station 74#90 to 19.1 feet per second at Station 40~00, downstream end of the levee. Riprap slope protection would be provided for the levee and thechannel slopes in accordance with Civil Works Engineer Bulletin 52-15,"SlopeProtection," and Technical Bulletin 2-265, "Velocity Forces on Submerged Rocks." Since the velocity against the channel banks would be less than the average channel velocity, a 12-inch layer of riprap is considered adequate for average channel velocities of 12 feet per second. The thick- ness of the riprap layer and filter blanket would be increased by 50percent when placed under water. Except for the setback levees between Stations 179/50 and 165160, riprap would extend from the top of the levee to an P elevation 5.0 feet below the lowest elevation of record of the bottom of E S the existing channel or proposed channel, whichever is lower. Riprap for C setback levees between Stations 179/50 and 165/60, left bank, would extend A from the top of the levee to the stripped foundation. Riprap will also be D E placed around bridge piers located in the channel. A six-inch layer of R filter-gradedsand and gravel would be required under all riprap placed 0 on fine grained materials exposed in the channel slopes. Following are 3 the required riprap thicknessesof the various reaches of the project 5 where riprap is placed above water level: 9 9 Stations Thickness of Riprap Layer

24 inches

18 inches

44/50 to 74/90 15 inches

74/90 to 127/36 12 inches

127/36 to 127/64 15 inches 1 /64to 179/5o 12 inches

B-9. / TOE DRAIN

Between Stations 90/00 and 140/00 on the right bank and between Stations llO/O0 and 123~00 on the left bank, where the overburden material is approximately 5 feet in thickness, a trench drain backfilledwith streambed sand and gravel would be placed 5°0 feet landward of the land- side toe of the levee. The trench drain would be excavated to a sufficient depth to tap the pervious zone of the foundation. This drain is provided as a safety measure against boils and piping behind the levee although the likelihood of excessive hydrostaticpressures developing at the toe of the levee is considered remote.

B-IO. TYPICAL LEVEE AND CHANNEL SECTIONS

Typical levee sections are shown on Plate B-11. The levee and channel slopes would be 1 vertical to 3 horizontalon the channelside. The levee slope would be 1 vertical to 2.5 horizontal on the landside. The crest of the levee would be 12 feet in width. A vertical core 12 feet wide consisting of fine grained impervious materials would be placed in the center of the levee. The central core would extend fromthe stripped foundation to 2 feet below the crest of the levee. The outer portions and the top 2 feet of the levee would be constructedwith streambed sands and gravels. All levee materials will be compacted to 95 percent of standard AASHOmaximumdensity. B-If. SOURC/ESOF CONSTRUCTIONMATERIALS

a. Ripra~.

The closest source of rock that has been approved for quality for use as riprap is at the Trinidad quarry, 20 miles to the south. The rock is hard, blocky greenstone that has an excellent service record from use in the Humboldt Bay jetties. Outcrops of Kerr Ranch schist along Redwood Creek within 1 mile of the project levees might be developed for use as a riprap but as yet the outcrops have not been evaluatedfor that purpose.

b. EmbankmentMaterials.

Embankment materials wouldbe obtained from the required channel excavation. Quantity estimates indicate that there~Lwotuld~a sufficient amount of sand and gravel and an excess of approximately 175,000 cubic yards of fine grained materials. The excess material would be wasted in the abandoned channel near the downstream end of the project. A SUl~plementalsource for sand and gravel would be the gravel bars located near the confluence of Prairie and Redwood Creeks.

c. //FilterMaterials.

Sand and gravel for the filter material would be obtained from streambed deposits within the project site. Some blending of these materials may be required to obtain the desired grading. Reference is made to Plate B-8 for the required gradation of the filter materials.

B-6 TABLEB-1 SUMMARYOF SOIL TESTS I~CHANICAL ATTERBERG DEPTH(FT.) FIELD ANALYSIS LIMITS SPECIFIC HOLE SAMPLE NO. CLASSIFICAT ION GRAVITY NO. H LL PI FRCM TO %0

22-5 9.5 14.0 Silty SAn~ (SM) 0 62 38 21 3 22-6 0 4.5 1 SiltySand (SM) 0 59 41 NP 22-7 7.8 9.7 3 Sandy ClayeySilt (ML) 0 ~0 70 28 2,76 22-10 0 5.4 1 Sandy Silt IC~ML) 0 4o 6O 35 9 22-10 1%.8 25.5 3 Sandy Clay 0 21 79 26 6 22-11 5.3 9.5 2 Silt (MH) 0 2 98 59 26 2F-14 7.5 8.9 3 Silty Sand (SM) 1 15 NP 2F-18 9.2 14.3 4 Silt(ML) 0 97 43 14 2.77 4B-I 0 i0.0 1 ClayeySandy Gravel(GW-GC) 66 27 7 21 4 2.70 CORPSOFENGINEERS U.$. ARM’

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P APPENDIX C E S C BASES FOR DESIGN AND COST ESTIMATES A D E R TABLE OF CO~I~TS 0 3 6 2 7 SECTION I - BASES FOR ~SIGN C-I C-1 PURPOSE AND SCOPE C-I

a. Purpose C-I b. Scope C-I

PLAN OF IMPRO~ C-I

a. General C-I b. Hydraulic design C-I c. Structures and improvements C-3 d. Drainage facilities C-4 e. Relocations C-4 f. Construction materials C-4

SECTION II - PROJECT COSTS AND ALLOCATIONS C-4

C-3 COST ESTIMATES C-4

a. General C-4 b. Federal cost C-5 c. Non-Federal costs C-5 d. Annual charges C-6 e. Aversge annual maintenance and opera- tion costs C’7

ALLOCATION OF COSTS AND IRTERESTS c-7

a. General C-7

C-i APPENDIX C

BASES FOR DESIGN AND COST ESTIMATES P E SECTION I - BASES FOR DESIGN S C A C-I. PURPOSE AND SCOPE D E R a. Pur2ose. This appendix is prepared to present details per- 0 tinent to the selected plan of improvement.It includes factors regarding planning design, cost estimates, and allocation of costs among interests in accordance with benefits to be derived. Studies have been made in conformancewith and pursuant to policies and pro- cedures set up in ~ ll20-2-101 and appropriate references thereto.

b. Scope. The scope of studies and the extent of information presented in this appendix are sufficient to support selection of the proposed plan of improvement,the features of design, and the conclusions and recommendationstherein. It will permit a satisfactory review by higher echelons, members of Congressionaldelegations, and interestedpersons.

C-2. PLAN OF IMPROV~T

a. General. The work proposed in this report would consist of channel improvementsalong the lower 4 miles of Redwood Creek. It woul~ include channel rectification~levees and partial revetment. A major channel change near the ocean would provide a more direct route for stream flow. A trapezoidal type chaunelwith riprapped side slopes would be used between river miles Oo8and 3.3, and the remainder of the project would be an offset-leveet~pe channel with partially rip- rapped slopes. The left bank levee would extend downstream from river mile 4 to about river mile 0°8. The right bank levee would extend downstream from river mile 3.3 to about river mile 0.8. The improved channel would be located to minimize disturbanceof developed areas in the town of Orick. It is considered that a relatively high degree of protection is warranted for the urban area. The design discharge selected for the project is 77,000 c.f.s., which is equal to the stan- dard project flood. This is about 50 percent larger than the greatest flood of record.

b. H~draulic design. Redwood Creek in the lower four-mile reach in the vicinity of Orick has a minimum bank full capacity of about 17,000 c .f.s. Observationsmud records have been made of the 1953, 1955 and 1958 floods, at which time waters inundated portions of the town of Orick and the adjacent farm lauds. Hydraulic design data were secured from tracings of enlarged aerial photographs,a line of field levels, and cross sections taken at about 1/4 mile intervals along the main stream within the project limits. Highest estimated tide

C-1 .~ is elevation 5.2 m.s.l, which is well below the design water surface at the dispersal area into the Pacific Ocean, smd is used as the starting point for backwater computations. The highest estimated tide would cause no increase upon stream stages under the project design flood, but would have some effect upon stages of low flow as far upstream as about River Mile 2. Proposed improved channel grade throughout the lower fo~ ~les of river is based on an average of the present stream thalweg, it is considered that the sandspit at the ocean would be lowered by scour to at least the proposed improved channel bottom and the opening at the peak of the 77,000 c.f.s, design flood would have a section equivalent to a bottom ~idth of 400 feet and side slopes of 1 on 3- The channel cutoff immediately upstream from the sandspit would be constructedwith a bottom width of 250 feet and 1 on 3 side slopes. There would be no levees in this lower reach and flood waters would overflow the low lying natural banks as occurs under present conditions. Even if the sanspit did not fully erode, it is considered that there would be adequate drawndown to preclude adverse effect on design water surface elevations. The next 3 miles of improvementupstream to about 0.8 miles above Highway U. S. lO1 Bridge at Orick would be a fully improved trapezoidalchannel with side slopes and levee face protected with dumped stone riprap. The channel would have a bottom width of 250 feet with 1 on 3 side slopes. The downstream 250 feet of the levees would flare to each side and have open ends. This would allow flood waters to spread and inundate some agriculturallands on the landward side of the levees, but to a lesser extent than under existing conditions. At about 0.8 mile upstream from the 0rick Bridge, the right bank levee would tie into high ground landward of Highway U. S. 101° From the upstream end of the trapezoidal channel, the left bank protection would consist of an offset-typelevee, with partial revetment, which would extend up- stream about 0.6 mile to tie into high ground on bench lands near river mile 4. The water surface profile was computed for the project design flood of 77,000 e.f.s, under improved conditions. Computations

~w~bythe backwaterfor the trapezoidal method usinga channel ManD~ings and~or coefficientoverbank areas. !’n" --S~a~c coefficients applicable to con~at the 0rick Bridge, the downstream open-ended levees and the upstream funnel effect were used to determine bridge losses and transition losses. Mean computed velocities are about 12 feet per second except at the lower end of the trapezoidal channel section, where velocities up to 19 feet per second would be experienced.A tabulation of stream velocities and a profile along centerline of improved channel are shown on Plate 2 of the main report. The improved direction of flow created by the proposed channel cutoff is expected to become a permanent condition and the old channel and slough .soul~ gradually become silted in. The only interior drainage that needs facilities through the levee is on the right bank about 800 feet downstream from Orick Bridge. It is proposed to install drainage culverts at this location and in order to prevent excess ponding behind the levee while the creek is in flood stage, it also will be

C-2 \ necessary to provide a pumping plant. The culverts have been ,designed to discharge the peak flow of 440 CofoS. caused by a lO0-year rainfall on the tributary ~hi]e Redwood Creek is at low stage. The pumping / plant is designed to dischargethe runoff ~from the 30-year storm on the ti~ibutarycoincident with occurrenceon Redwood Creek of the project / design flood of 77,000 c of.s. dischai~ge° The required pumping capacity // is 40 ~.f~s. This hyc~raulic design is equivalent to criteria set up J% by ~-~Ci~v!l Works Construc~ion~_PartcX=TV~_ Chapter ~ for Class u-i (Urban Commercial)oThe proposed degree of protectiqn is considered adequate and would allow ponding behind levees without appreciable damage. Details of drainage facilities and the location of pump plant are shown on Plate 2 of the main report. The culverts would be equipped with automatic flapgates at the discharge end, emergency slide gates at the ~i~ward side of the crest of the levee,~~on- c~ headwalls as re, red.

c Structures and imorovementso The principal features of work proposed are charm.el excavation,levees and revetment° The trapezoidal channel and the channel cutoff near the ocean would have a minimum bottom width of 250 feet. Channel excavation and bank shaping would not be carried below the bottom of improved channel, except for toe trench excavation and formationof the temporary low-flow fish channel. All excavated channel slopes would be 1 vertical on 3 horizontal. The fish channel required by U. S. Fish and Wildlife Service and California Fish and Game Department would have a six-foot width and a one-foot depth. The levees would be constructed with slopes of 1 on 3 on the channel side and 1 on 2.5 on the landside. The finished crest of the levee would have a 12-foot ~idth. A central core of impervious material 12 feet wide would extend from 2 fee~~ below top of levee to the stripped earth foundation. The outer and top portions of the levee would be made of streambed sand and gravels secured from designated reaches of the chanuel when constructionis performed. The impervious central core would be made of the fine-grainedmaterials secured from channel excavation and bank shaping. Applicable shrinkage factors have been applied to levee embankment quantities in determiningthe amount of material required° Road approaches and passing turnouts would be made as found necessary. Slope protection would be provided by a blanket of dumped stone riprap ~hich would vary from 12 to 24 inches thick. The thickness would be increased by 50 percent when materials are placed in water° Throughtout the trapezoidal section, the bottom of riprap would be placed five feet below improved channel bottom or natural stream thalweg, whichever is the lower. Along the offset- type levee, the riprap would be placed on the stripped foundation. All riprap would extend up to the elevation of top of leve~. A six-inch thick blanket of filter gravel would be placed over all fine grained material prior to placement of riprapo ~is gravel thickness would be increased also by 50 percent when placed in water~ Riprap would be extended around the flared levees at the lower end and would extend upstream a distance adequate to prevent erosion of the levees. Transition

c-3 of riprap to unrevetted levee faces would be designed as required. See Plate 2 of the main report for general details of the slope pro- tection and stream velocities under improved conditions.

d. Draina~me facilities. Facilities for drainage from behind the levees would be provided as described in the precedingparagraph on Hydraulic Design. Ponding areas where accumulationsof local runoff might occur during high flood stages and location and i~_~ofPiPe~s~ ~ are shown on Plate 2 in the main report. A toe-drsln on the landward side of the levee would be required along a reach on each side of the stream. ~is would relieve saturated conditions of levee embankment and would concentrateinterior drainage downstream from the business center of 0rick. See plan on Plate 2 of the main report for location.

e. Relocations. The proposed project would require relocation of several small buildings near the banks of the river. Relocation of county roads, private roads, and raising of Highway U. S. lO1 at the upstream end of the right bank work ~uld be required° Incidental amounts of fence reconstruction;sewer and water &rain extensions or closures; and telephone, power or other pole limes changes would be required. Relocation costs are a responsibilityof local interests and details are itemizedin Table C~-2.

f. Construction materials. Materials for construction are available within econo~Licdistances, as discussedin detail in Ap- pendix B.

SECTION II - PROJECT COSTS AND ALLOCATIONS

C-3. COST ESTIMATES

a. General. Unit prices used for estimates in this report are based on price levels as of July 1960. In establishingthese prices, considerationwas given to bid prices for similar type work in northern California areas during recent months. An allowance of 20 percent has been included for all contingencieson constructionitmes. The total cost of the project is estimated at $2,900,000. The principal features of cost are sho~u~ in the followingsummary:

SUMMAEY OF PROJECT FIRST COSTS

Costs Feature Federal Non-federal Total

Channels $ 72 5,000 Levees i, 445,000 Relocations $i10,000 Lands Easements R/W 160,000

C-4 Costs Feature Federal Non-Federal Total P E PreauthorizationStudies $ 50~ 000 Engineering and Design 190~000 A Supervision and Administration D E X Total cost $2,630,000 $~ 270, ooo$ z, 9o%ooo 0 3 G 3 b. Federal cost° Government first costs are considered/as gross 3 amounts before determinationof participationcharges to local interests due to land enhancement benefits. The items of work have been~separated into major features of work in accordance with the Uniform Cost Account Numbers. Waste excavation includes removal of materials which cannot be used in levee embankments°The fine-grainedmaterials of overburden along the stream wouldbe used in the outer portions of the levee. The zone of impervious material could be placed @n slopes up to 1 on 1 in order to use large amounts of overburden channel excavation,if necessary. Drainage facilities have been shown as a lump sum item. In- direct costs include amounts for preauthorizationstudies, engineering and design, and supervision and administration°These include en- gineering costs for preparing a design memorandum and plans and speci- fications. Supervisionand administrationincludes costs for surveys, investigations,supervision and A~spection of constructionand dis- trict overhead. Total gross Federal first cost of the project is estimated at $2,630,000,of which $450,000 is the estimated amount of government costs° Preauthorizationstudy costs of $50,000 are made up of the portion of the PreliminaryExamination Report costs and the

portion of the Survey Report costs considered applicable to the channel i improvement project proposed herein° It is estimated that $4,000 of the funds expended for general investigationstudies are applicable to dam studies which are not a part of the work recommendedfor authorization. See Table C-1 of this Appendix for detailed estimate of Federal cost. Costs for the principal items of work are ~ized in the main report.

c. Non-Federal costs. Costs to local Interes~include: (i) lands, easements and rights-of-way~and (2) relocation of Utilities including structures, roads, pole lines, and miscellaneous facilities. The cost of land includes rights-of-wayand easements for constructionof pro- posed project and access at all times for maintenanceand operationof’ the project. The rights-of~wayhavebeen estimated at current market value for lands needed for construction°This is all lands within the extreme outer edges of constructionplus a lO-foot work area strip on the border and side of the levees. The affected lands are in four price categories: river channel, rural, undeveloped urbananddevelopedur~n.

c~5 Increased land use is considered applicable to undevelopedurban la~ds on the left bank which lie between and adjoin two portions of the developed portion of 0rick. Costs for acquisition have been estimated at lO percent of the land costs. Total non-Federal costs are estimated at $270,000 which is about l0 percent of the total gross Federal constructioncost. r ......

d. Annual char~es. Average annual economic costs are approximately one percent greater than the average annual financial costs, as a result of loss of land productivity. For the purpose of this report, only the average annual economic cost is presented. The estimate of average annual costs is based upon a 50-year economic life of project. Interest rates are~ based upon the expected average long-term return on risk-free investments and are in accordance with the latest applicable Federal and non-Federal rates. The adopted rates of interest are 2-5/8 percent for Federal costs, and 4 percent for non-Federal costs. A 5 percent interest rate is used for lands, exclusive of acquisitioncosts, to allow for loss of productivityof the lands within the project bouudaries.The Federal interest~ rate conforms to the current rate established by the Bureau of the Budget. The rate for the non-Federalcost is that furnished by the State of California and is co~idered applicable since the period of constructionis less than two years and benefits are expected to accrue simultaneouslywith construction. Costs for maintenanceand operation, and replacementsare a non-Federal responsibilityand are important in determiningtotal average annual char- ges for the project. These costs are included in the following derivation and details of the value are shown in the next paragraph.

AVERAGE ANNUAL CHARGES Federal First constructioncost Interest and amortization(.03614 x 2,630,000) $2,630,000I./’ 95,000 Non-Federal First constructioncost Interest and amortization(.04655 x 2701,000) 270,000 13,000 for loss of prod_uctivity ~ustment¯o5 - .o4)x 148,ooo) Maintenanceand operation i,500 19t500 TOTAL NON-FEDERALANI~JAL COST TOTAL AVERAGE ANNUAL COST ,34~00o 129,00o l~ Includes PreauthorizationStudies Costs

c-6 e. Average annual maintenance and operation costs. The estimate-for average annual maintenanceand operation costs is an amount considered realistic for the average amount of money needed each year to keep the improved project in condition to function satisfactorilyfor the life of the project. It is based on an amount for repair of the project including an amount for replacementof culverts and gates within a 30-year period. This average annual maintenanceand operation cost is estlmated at $19,500 and is derived as follow

Channel clearing and snagging B mi. @ $3,000 $9,000 Levee repairs 7 mi. @ 300 2,000 3 6,500 6 Revetment 6.5 mi. @ l, O00 3 Drainage facility maintenance B and replacement lump sum l, 500 Flood patrol, engineeringand overhead, lump sum 5oo,

Total average annual M & O 19,500

0-4. ALLOCATION COSTS AMONG INTERESTS

a. General. The plan of improvement proposed herein is for the single purpose of preventing future flood damage in the community of Orlck and the adjacent dairyland area~ Therefore, an allocation of costs among purposes for project i~nctions is not required. TABLE C-I

Detailed Estimate of Federal Cost P (J1tly 1960 Price Levels) E S C Survey Report - Redwood Creek, Humboldt County, California A D Cos t E R Account Unit Feature 0 No. Feature end Item Unit Price Quantity Amount Cost 3 6 09. Channels $725,000 3 7 Stripping,waste C.Y. $0.25 140,000 $ 35,000 Excavation,pervious C.Y. 0.60 463,000 278,000 Excavation,impervious C.Y. 0.65 294,000 191,000 Excavation,waste C.Y. 0 ~35 287,000 i00,000 Contingencies,20% 121,000

ll. Levees $i,455,000 Clearing and grubbing Job L.S. 1 26,000 Embankment,pervious C.Y. 0.25 390,000 98,000 Embankment,impervious C.Y. 0.40 113,000 45,000 Backfill, toe-trench C.Y. 0.35 2,800 I, 000 Riprap Ton 4.50 184,000 828,000 Filter gravel Ton 2.50 60,000 150,000 Drainage facilities Job L.S. i 17,000 Pump Plant Job L.S. i 50,000 Contingencies,20% 240,000 Sub-Total, Gross Federal ConstructionCost 2, 180,000

29. PREAUTHORIZATIONSTUDIES 50,000 30. ENGIN-~NG AND DESIGN 190,000 31. SUPERVISIONAND ADMINISTRATION 210,000

’-TOTALNON-FEDERAL FIRST COST $ 2, 630,000

TABLE C-i TABLE C-2

DETAILED ESTIMATE OF NON-FEDERALCOST (July 1960 Price Levels)

Survey Report - Redwood Creek, Humboldt County, California

Unit’ Feature Feature Unit Price~ Quantity Amount Cost

RIGHTS-OF-WAY $16oooo

Lands and easements

River channel Acre $ i0 90 $ 1,000

Rural Acre 700 70 49,000

Urban - undeveloped Acre 3,000 3 R,O00

Urban - developed Acre 4,500 14 63,000

Acquisition,10g 12,000

Contingencies,20% 26,000

RELOCATIONS SiIo,000

Buildings Job L.S. I i0,000

Roads Job L.S. I 60,000

~Utilities Job L.S. i 20,000

Ccntingencies,20~ 20,000

TOTALNON-FEDERALCOST $270,000

TABLE C-2

APPENDIX D P E S FLOOD DAMAGES AND FLOOD CONTROL BENEFITS C A D E TABLE OF CO~TE~S R 0 Paragraph Title 8 6 SECTION I - GENERAL 1 PURPOSE AND SCOPE D-I LOCATION AND DESCRIPTION OF BASIN D-I POPULATION D-2 OCCUPATION AND INDUSTRIES D-2 AREA SUBJECT TO INUNDATION ~B

SECTION II - FLOOD DAMAGE ANALYSIS

~6 GENERAL D-7 HISTORICAL FLOOD DAMAGES D-8 FLOOD DAMAGES UNDER PRESE~ CONDITIONS D-9 AVERAGE ANNUAL DAMAGES D-IO ADJUSTMENT FOR ANTICIPATED ECONOMIC DEVELOPME~ D-11 AVERAGE ANNUAL DAMAGES

SECTION III ® FLOOD~CONTROLBENEFITS

D-12 BENEFITS FROM FLOOD-DAMAGEREDUCTION I~13 LAND-ENHANCEmENT

SECTION IV - PROJECT BENEFITS UNDER 100-YEAR PERIOD OF ANALYSIS ~9 POLICY AND CRITERIA ~9 SUMMARY AND COMPARISON OF FLOOD-CONTROL BENEFITS D-lO

Number PLATES

D-I FLOOD DAmaGES AND FLOOD CONTROL BENEFITS APPENDIX D

FLOOD DAMAGES AND FLOOD COI~I~OL BENEFITS P E SECTION I - GENERAL S C D-I. PURPOSE AND SCOPE A D E The purpose of this appendix is to present the findings concerning R 0 present and anticipatedfuture flood damage and prospectivebenefits from possible flood-controlimprovements in the Redwood Creek Basin, California; 3 the scope of the investigations;and the procedures followed in developing 6 4~ the estimates of present and future flood damages and prospectivebenefits. 3 Investigationswere made of flood damages and possible benefits frc~ flood- control improvementsthroughout the developed sections of the basin. Particular attention was given to the areas which would be affected by channel improvements along the lower reaches of the creek. Estlmates were made of flood damages and possible benefits from flood control over periods of 50 and lO0 yesms pursuant to Senate Resolution 148, amended 28 January 1958, and recorded in Volume 104, pages lO18 and lO19 of the Congressional Record. The amended resolution states in part, ’With respect to the pro- ject recommended for authorization~the information~hould include, but not limited to o.. benefit-costfor lO0 years and 50 years, except where the economic life of the major proSect facility is less."

D-2o LOCATION AND ~ESCRIPTION OF BASIN

Redwood Creek drains an area of approxim~+~ly283 square miles located entirely in Humboldt County. The drainage basin is roughly rectan- gular in shape, extending about 56 miles along a northwest-southeastaxis, and having a maximum width of about seven miles. With the exception of the lower five miles, the stream flows through a narrow deep canyon. The flat valley area contains approximatelyl~000 acres of agriculturallands, practically all of which are devoted to dairy farming and production of forage crops. Elevations of the drainage basin vary from sea level at the ocean to 5,000 feet mean sea level at the southeasternextremity of the basin. The largest tributary is Prairie Creek which drains the northern part of the basin and joins Redwood Creek just upstream from the town of Orick. The terrain is mountainous and heavily wooded. Level land is found in small areas along the streams. The only significant area of level land is located along the lower four miles of the stream, which con- tains the town of Oricko The problem area of this investigation is the channel and flood plain of the lower four miles of Redwood Creek, ap- proximately from the confluence with Prairie Creek downstream° Develol~ ments in the area are the town of Orick, about five sawmills, one large loggimg pond, and about 1,O00 acres of relatively flat agricultural lauds.

D-1 D-3. POPULATION

The basin population is approximately2, 500. Historic population data for H~mboldt Coun’t~ indicate that the county has experiencedrapid growth since 1940, as illustratedin the following tabulation:

Humboldt Count~ and NorthwesternCalifornia

Humboldt Year , County 1910 33, 847 192o 37,413 1930 43, 233 194o 45,812 1950 69, 241 1960 104,308 1970 125,000 198o 157,ooo 1990 200,000 2000 250,000 2010 290,000 2020 340,000

The population in Orick postal district has been estimated to be about 1,800 of which about one-half resides in the town or Orick. Population forecasts for 0rick are analyzed more fully in paragraph D-10.

D-4. OCCUPATION AND INDUSTRIES

Redwood Creek drainage basin is situated in an area important for its extensive stands of timber. Although there are substantial quanti- ties of Douglas Fir, California Redwood is the most important timber resource. Timber in the drainage basin has been estimated at about five billion board feet. A large part of the timberlands are operated on a sustained-yieldbasis which reduces the threat of depletion of timber resources and assures the economic future of the area. M~ch of the com- mercial and practically all of the industrial activities in Orick are dependent upon the lumber industry. The remainder of the commercial sector of the economy consists of stores, motels, service stations, garages and other service oriented enterprisesneeded to accummodatethe community. Other commercial activities provide service for hunting and fishing enthusiasts of the nearby mountains and streams. The Orick area is near two State parks with campgrounds. Practically all the areas suitable for agriculturein the Redwood Creek basin are located within the proposed project l~ts. Agricultural activities are devoted mainly to the dairy industry. The area is noted for its small dairies and hlgh-grade Guernsey cattle°° There is some raising of beef cattle, sheep, and forage crops. Agriculture is not diversified in this area. Climatic conditions are favorable to field and forage crops and livestock P raising as a general rUle, but not favorable to growing truck or orchard E crops. Highway U.S. i01 is the princilx~l transportationroute serving t~ the Redwood Creek dmainage basin, and the only main highway al0mg the A north coast of California° The upstream portion of the basin is tra- D E versed by Highway U.S~ 299, the transmountainhighway from the Pacific R Coast to the Sacramento Valley° Bus and truck lines provide passenger O and freight service for the area. 3 6 ])-5. AREA SUBJFL~ TO INUNDATION 5 The area subject to inundation within the limits of the proposed project begins approximatelyat the confluence of Prairie and Redwood Creeks and extends downstream to the mouth. Subsequent economic deter- minations in this report are based on this specific area, unless other- wise stated. See Plate 1 in the main report for delineation of flood plains. This reach of the flood plain contains most of the agricultural area, the town of 0rick, and several lumber mills° The agricultural area is estimatedat about 1,O00 acres; the urban development,residential, commercial and industrial developmentscover about 275 acres; and water- ways,~ uncultivatedlands, and wastelandamount to about 675 acres for a~ total of 1950 acres. The estimated gross value of land and improvements in the flood plain is summarizedin the following tabulation:

Residential $ 4, 375,000 Schools and churches 725,000 Commercial 2, 000,000 Industrial 2, i00,000 Agriculturallands and improvements it 300t 000 Total $i0,500, 000

SECTION II - FLOOD DAMAGE ANALYSIS

Floods result from high intensity rainstorms. The season for sig- nificant storms usually extends from October through April. Flood- waters cause extensive damage by inundation,bank erosion, flood wash of top soils, and debris deposition° Damages are sustained by urban, business and industrial properties;and by agriculturallands, crops, and developments. Three floods of damaging proportions are known to have occurred during the last decade° The floods of 1953 and 1955, the greatest ever recorded with discharges of 50, 000 c.f.s., each inundated the ~usiness section of Orick and the adjacent farmlands to depths of 4 feet. Flood damages will increase as additional developments continue and more people reside in or travel across the flood plain. Flood-&~ge surveys were made for the floods of 1950, 1953 and 1955. These ap- praisals were supplemented by historical data on floods of earlier years. All available sources of information were used by field ap- praisers to determine damages. Care was exercised in separating flood damages due to local conditions from main streamflow and tributary flow. The following paragraphs present detailed flood damage data and describe methods used in flood damage analysis under conditions at the time of occurrence and adjustments made to represent present conditions. Only the tangible flood dsmages are evaluated on a monetary basis. In- tangible flood dsmages such as loss of life, impairment of health and living conditions, loss of ability to obtain credit, and other factors not subject to monetary evaluation are not included.

D-7. HISTORICAL FLOOD DAMAGES

Information obtained at the 1955 Public Hearing in Orick indicates that flooding in the Orick area occurred as early as 1890. Large floods Occurred in the years 1921, 1927, 1935, 1937, 1950, 1953 and 1955. Some flood overflow occurs about every other year and considerable bane erosion is almost an annual occurrence. Urban, and rural damages from the 1953 and 1955 floods were heavy and widespread. Approximately 1950 acres were flooded to depths of about 4 feet in 1953. The stream rose with such rapidity that salvage operations were held to a minimum. Resi- dences, stores and other establishments were temporarily abandoned to the floodwaters. Practically all homes and business establishments in Orick were flooded. Large supplies of stored foodstuffs were destroyed. Lack of transportation facilities hampered the delivery of stocks to replace those destroyed by the flood. Floodwaters overflowed State and county roads in the basin, and traffic was suspended for 12 hours during the peak of the flood. Due to highway damage and non-functioning drains~e facilities, the highway was closed over 48 hours. The Orick Bridge, Join~ the two parts of town, was endangered when the left bank of the creek and the approach fill began to erode at a rapid rate. State h~way maintenance crews worked continuously during the peak of the flood %0 protect the bridge. Several large sawmills were badly damaged and required extensive repairs. Plants were shut down while repairs were made. The lay-off of workers necessitated by temporary closing of the mills had some detrimental effect on the economy of Orick. Agricultural damages consisted principally of scouring and eroding of land; deposi- tion of silt, gravel and other debris; and destruction of some pasture. Damages along Prairie Creek, a major tributary of Redwood Creek were not severe. The flood of December 1955 was approximately equal in magnitude to the flood of Jantlary 1953. Some areas along Prairie Creak, which sustained damage during the 1953 flood, were not affected. Of the 1,800 acres of flooded area, exclusive of water areas, approximately 910 acres were agricultural lands° Inundation of non-agrlcultural facilities in the basin was about the same as in 1953. Secondary peaks P E during the latter part of December and early part of January, sad sub- S sequent rises of Redwood Creek, flooded some areas previously flooded, C but the additional dsmage was light° The variation in damages resulting A D from the floods of 1953 and 1955, which were approximatelyequal in E magnitude, is accounted for mainly by the fact that effectivel~reeautionary R 0 measures were taken during the 1955 flood. As a result of the 1953 flood, local residents were alert to the hazard which they faced. In addition, 3 there was sufficient warning to permit the removal of a large number of 6 4~ house trailers,home furnishings,merchandise stocks and other items. 7 Also, some properties located along Prairie Creek which suffered damages in 1953 were not flooded in 1955. There were no reported damages in the upstresm areas of the basin in 1955 although these areas were severely damaged in the 1953 flood. Flood damages for a flood of the magnitude of the 1950 flood were estimated on the basis of damage sustained in 1950 adjusted to present conditions of developmentand 1950 price levels. Damsges from the floods of January 1950, January 1953 and December 1955 within proposed project limits at the time of the event are tabulated below: January1950 January1952 December1955

Discharge 37,000 c.f.s. 50,000 Cof.S. 50,000 c.f.s. Agricultural $ 68,000 $ 106,900 $ 51,600 esidential 17,000 191,5oo 68,7oo Co~®ne.rcial 26~ 000 296,200 215,400 Industrial i, 000 115,000 45, 400 Public utilities 20; 000 231~700 187~lO0 $132,ooo $ 941,300 $ 568,2oo

D-8. FLOOD DAMAGES URDER PRESERT CONDITIONS

In order to present damages at April 1950 price levels~ the his- torical flood dzta was brought to 1960 prices by the applicable price index developed from the following price indices: Agricultural

(ProductionItems)

C~ercial-l_r~ustrial (Constructioncost) 509.62 599.99 659°72 813.58

Residential (~ldir~cost) 375.47 430.78 468.80 555.23 Public facilities (Constructioncost) 509.62 599.99 659.72 813.58

Recurrence of recent floods would cause damages within the limits of the improvementsunder 1960 price levels and developaentsas shown in the following ~ation. In addition, the estimated damages for a flood of standard project magnitude are tabulated.

HISTORIC FLOOD DAMAGES (within project limits only)

(April 1960 Price Level and Development) s~ Type 1950 1953 1955 Project Floo~ ~ricu~tural $ 82, ooo $ ~5, ooo $ 56, ooo $155, 0oo Residential 24, O00 245,000 81, 000 344,000 Commercial 41, 000 403, 000 266,000 568,000 Industrial i, 000 156,000 231,000 206,000 Public facilities 32, 000 315~000 56~ 000 447,000

Total $ 180, 000 $i,234, 000 $ 690,000 $i, 720,000

Total damages sustained in the Redwood Creek Basin from the 1953 flood, based on April 1960 price levels, amount to $1,774,000. Of the total dsmages, $1,234,~ were sustained within the limits of the proposed proj- ect and about $520,000 were suffered in the upstream reaches of Redwood Creek. Damages on Prairie Creek in 1953, resulting from streambank overflow, were about $19,000. D-9. AVERAGE ANNUAL DAMAGES

Average annual damages are computed by standard damage-frequency P analysis. ~he flood frequency curve developed in Appendix A, Hydrology, E S is used as a base for graphic developmentof the followingeconomic C analysis. A discharge-damagecurve was prepared by plotting l~Lst damages A adjusted to present economic conditions for the 1950, 1953, 1955 floods D E against the recorded discharge of those floods. As a fourth key-point R in the graph, and to assist in shaping the curve, damages were estimated O for the standard project flood. The curve was drawn to reflect average 3 conditions in general. There are no assurances %hat a warning in the 6 future would be as effective as that which occurred in the 1955 flood, 4~ 9 when there was full evacuation of personnelj nearly complete evacuation of movable equipment and partial removal of business stock and furnii-ure. Da~a from these curves determined the damage-frequencycurve; plotting the amount of damage against the frequency of the discha ge which would cause such damage. IMmmge-frequencycurves were prepared for conditions without and with the proposed improvements°Average annual damages were estimated by conversion of the area under the damage-frequencycurve to its equivalent value in dollars° Total average anmml damage~within the proposed project area and on the basis of 1960 price levels is estimated at $188,000.

D-IO. ADY0B~4ENTFOR ANTICIPATEDFUTURE ECONOMICDEVELOPMERT

Floed-damagestudies have shown generally that in the future average annual flood damages may be expected to increase with the increase in the economic development in the flood plain. Estimates of damages~ based on a 50-year project life and based on April 1960 prices and con- ditions, require adjustmentsto reflect the changes in increased popula- tion, and developments.Factors influencing new developmentsand improve- ments are discussed in the following paragraphs° In l~ragraph D-S, data on population for Humboldt County were presented° Information on small unincorporatedurban communities,of which Orick is one~ do not follow specificallythe general trend of increasesshown for Humboldt County. Because of the geographic location and the specializedpattern of develop- ment in this area, the trend will follow generally the past pattern. The large concentrationof urban population and industrial and commercial activities are expected in those areas which now have the largest urban population and offer the greatest economic potential. The forecast of economic activities for the Orick area is based in large part on the developmentand rise of recreation resources which are expected to become a major economic sUppOrt for the area° Economic activities associated with the recreation resources, consist predominantlyof services to tourists, sports enthusiasts,and others residing in the area because of the natural attractions°The projection of development trends has been guided by studies in the field of economic geography which show that, as a large rural region becomes more highly developed, its pattern of economic and population growth follows certain trends ° Amo~ these factorsinfluencing the polxulationtrend are:

a. The proportion of total employment in the region provided by extractive activities (agricultural,forestry and mining) and in the manufacturimgof products from local natural resources (i.e. lumbering) steadily declines.

b. Employment and population in urban sections of the region grows more rapidly than employment and population in the rural sections with consequent increases in the proportion of urban population in the region.

Based on the foregoing, economic developmentfor the 0rick area is related to polmlation increases for Humboldt County and for the north- western California area. The poFalation forecast for the Orick area has been estimatedto be about 5, 200 by 2,010, representingan increase of 190 percent over the base. The present population of the town of Orick has been estimated at about 900, with 1,800 for 0rick and vicinity. While the county population has increased significantlyover the last 30 years, the Oriak area has not increased proportionately.With general polm~ation increases expected in California and along the Pacific Coast and the anticipatedlomg-term increase in recreation activities,it is estimated that the (Frick area will participatein this growth. The rate of growth, however, is projected over a deferred growth-ratecurve as it appears that future growth will probably follow such pattern. Given these considerations,the damages were adjusted in direct proportion to projected population increases. Therefore, it is estimated that develop- ments amounting to 190 percent of the base would occur during the 50-year period from 1960 to 2010. On this basis, average mammal flood damages for April 1960 conditions would increase by 190 percent during the next 50 years. However, it is necessary to reduce this percentage increase to its average annual equivalent° When this is done, the average annual equivalent increase is equal to 32 percent of the 1960 development. Therefore, the average smaual dsmages for the project are increased 32 percent to reflect these changed conditions.

D--II. FUTUREAVERAGE ANNUAL DAMAGES

Future average annual damages are obtained by increasing the present average ~ damages of $188,000 by 32 percent, which results in an ad- justed fUture average anm,_al damage estimate of $248,000.

SECTION III - FLOOD-CONTROL ]~EFITS

I)-12. BENEFITSFROM FLOOD-DAMAGEREDUCTION

Benefits from flood-damagereduction creditable to the proposed improvements,with protection against the standard project flood of 77, 000 c.f.s., are the differencein damages with and without the pro- tective improvements°Residual damages of $20,000 are therefore adjusted by the 32 percent increase and ~mount to $26,000° These residual damages P with the project in effect would accrue to approximately200 acres in- E S clud~L~g develolnentswhich lie downstreamfrom the improvementsor would C be affected by flood overflow flankimg behi~ the open-ended levees. A D Flood-controlbenefits creditable to the project are estimmted at E R 0 3 6 5 Land-enhanc~ut benefits are those benefits expected to accrue 1 as a result of higher laud utilizationthan that which woul~ take place without the project and which, on an annual basis, are equivalent to the net increase in earning power of the land and property involved. La~d-enhaucementbenefits in these studies are considered under two categories, agriculturaland urban° The agricultural area subject to flooding amounts to 1,000 acres° Practically all of this area is devoted to forage crops for the dairy enterprises in the area° There are a~out 800 acres of Class I soils in this area which would be suitable for higher income crops. The economy of the agriculturalareas, however, has been devoted to dairying for many years. It is estimated~ that even if a flood-controlproject were constructed,there would be no signifi- cant change in this land use° As a result, no agriculturalland-e~aance- ment benefits are considered for project conditions o Under proposed project co~itions, there are some urban areas in the flood plain which undoubtedly would undergo chmmges to higher uses° The areas most likely to be affected, approximately50 acres, are located on the left bank close to the stream in the downstream portion of Orick. Value of these lands under present conditions is estimated to be about $800 per acre. Land developmentcosts such as constructionof utilities, streets, and sanitary facilities are estimated to be about $1,500 per acre. Based on preset information,the future estimated value of these lauds with propose~im~rovementsis estimated to be about $5,000 per acre. This represents a gain in value of $2,700 per acre or $135~000 for the higher use areas. In this connection, it is believed that the total increase in land v~lue would accrue within a period of approximatelyfive years after construction.Reducing this amount to its present worth with a five percent interest rate~ results in an average annual equivalent of $121,000. Using a five percent interest rate to convert this to an annual amount results in an average annual benefit due to land-e~hauce- ment of about $6,000.

SECTION IV - PR~-ECT BENEFITS UNDER 100~YEAR PERIOD OF ANALYSIS D-14. CURRERT POLICY AND CRITERIA . In accordancewith current Corps of Engineers’ policy and criteria, studies of the economic feasibilityof constructingflood-control works

~9 in the Orlck area on Redwood Creek are based upon a 50-year economic life of the project. Pursuant to Senate Resolution No. 148, subparagraph3, computationsof benefits creditable to the proposed project have also been analyzed on the basis of a lO0-year economic life. Average annual flood damages and flood-controlbenefits under present conditions would be the same over a 50- or lO0-year economic life. The future average annual flood damages and flood-controlbenefits, however, would change in an upward direction if the economic developmentof the area in question were greater over a lO0-year period than a 50-year period. There is suf- ficient land area to sustain the future growth anticipatedfor the first fifty years. In the extension of population projections fr0m which future economic developmentfactors are computed, it is estimated that the rate of increase the second fifty years would be about one-half the rate experienced in the first fifty years of the project llfe. On a per- cent basis, this represents an increase of about 330 percent, or about 6,000 increase over the present population for the area° When considera- tion is given to the fact that the increase occurs over a 100-year period and this prospectiveincrease is deferred over this period with a five percent discount rate, the average aanual equivalent increase is ap- proximately 49 percent of the base. Therefore, the average annual damages and flood-controlbenefits on the 1960 price level are increased, multiplied by 1.49 to reflect average conditions expected to prevail over this lO0-year period. Average amra~l damages thus increased amount to $280,000 and residual damages under project conditions amount to $30,000. Flood-controlbenefits for the lO0-year period of analysis amount to $250,000. In computing land enhancement benefits for the 100-year period, it is considered reasonable to adjust computed damages and benefits for the 50-year period in accordance with the population forecast for the longer period. Population forecasts for the area show an estimate of about 7,800 which represents a 50 percent increase over the base 2010. Computationsshow that with the 100-year period, average annual land-enhancmmentbenefits amount to $9,000.

D-15. S~U~ARYAND COMPARISONOF FLOOD~CO~I~ROLBEHEFITS

From the comparison shown below, the average annual flood-control benefits creditable to the plan of improvementon a lOO-year period of analysis are seen to be about i0 percent higher than those based on the 50-year period.

Peziod of Aual~sis 50 years I00 years

Flood-controlbenefits $ 222, 000 $ 250,000 Lam~- enhancementbenefits 6 ooo 9t ,ooo

Total $ 228, 000 $ 259, 000

I~lO ¯ ...... U.S.ARMY \

I00 U n~ 0 I.-- 80 Or) ECT 0IJ. 0 0 I; PROJECTCONDITIONS 60--t/ :" ¯ j ¯ DEC.i!~ ~ ¯ JA,.1953 ~ " EXISTINGCONDITIONS <"1"40 I Q I

20r ’/

DISCHARGEIN I000GFS ATORICK DAMAGEIN I00,000DOLLARS I’) I! 1,1. 18 It ZO f r ¯ ~p PROJECTCONDITIONS ~-~-~-~" I INGCONDITIONS AVERAGEANNUAL DAMAGE EXISTINGCONDITIONS $ 188,000 PROJECTCONDITIONS" 20OL~QO BENEFITS~ 166,000 PRICELEVEL APRIL 1960 _~L I II I I JlJFLOOOCONlfJlROL ill ...... REDWOODSURVEYIRAIK’JICREEK -J~IOTEDATA IS FOR DAMAGES ANDBENEFITS .~_ PLeODHUMIIOLDTDAMAeES CO.tAND P.~LIFOIII& IE~FITI WITHINPROJECT LIMITS ( ~IEFERENCE F LOODDAMAGES DISCHARGE--FREQUENCY CURVEIN ANOFLOOD CONTROLBENEFITS APPENDIXA-- HYDROLOIY). SHEETNO.I UIN.$1SHEET: DRAWN,.. AI~MYW.M,ENGINEER J, DtS[.,SAN FRANCISCO, F~LECOF NO.E ’~RA~ED:~.L.TOACCOMPANY REPORT CHEC.,K[D:W,It. a. DATED:PLATEAUI; II~D-~i~. I .~ ~.~ ~/ &..

P E S C A D E R 0 3 6 5 5 APPENDIX E

~OMMEN,~o ~iOF...... ~~,0 AOENCIES

P E S C A D E R O 3 E-1 SCOPE E~I 6 5 SECTION!i -~ FEDER$~LA~ENCIES 7 E-2 Uo So FISH AND WILDLIFE SF2J~ICE E-I

E-3 BUREAU OF PL~LIC ROADS E-I

E-A BUREAU OFRECLAMA~ION F~I

E-5 Uo So SOIL CONSERVATIONSERVICE E-I

E-6 PUBLIC HEALTH SERVICE E-2

SECTION~I o=, ~ .... A~EN~:ES

E-7 STATE OF CALIFORNIA E,~2

SECTION IV - RESOLUTIONS

E-8 SPONSORING AGENCY E~2 APPENDIX E

COMMENTS OF OTHER AGENCIES P E S SECTION I - GENERAL C A D E-I o SCOPE E R 0 In accordance with departmentaland interagencypolicy, coordination with Federal and non-Federalagencies has continued during investigationof 3 Redwood Creek for flood control and allied purposes° This appendix presents 6 5 the comments of these agencies relative to the recommendedplan of improve- 9 ment which proposes channel improvementsin the lower reaches of the stream° Discussionof the comments is also included.

SECTION II - FEDERAL AGENCIES

E-2o Uo So FISH AND WILDLIFESERVICE

Exhibit A of this appendix presents the comments of the U. S° Fish and Wildlife Service~ Five recommendationsare made which the Service states will minimize the adverse effects the project would have on fish and wildlife resources° The comments will be given full consideration during definite project studies.

E-3. BUREAU OF PUBLIC ROADS

The Bureau of Public Roads finds that Highway US-IOI, Federal-aid Primary Route No. l, will require raising at one location° Inasmuch as the design has been coordinatedwith the California Division of Highways, the local agency directly responsiblefor the affected Federal-aidhighway, the Bureau’s interests appear satisfied, as stated in Exhibit B.

E-4. BUREAU OF RECLAMATION

Exhibit C of this appendix presents the comments of the Bureau of Reclamation°The Bureau finds that the recommended improvementsdo not con- flict with any of its existing projects or plans.

E-5o Uo So SOIL CONSERVATION SERVICE

The comments of the U. S. Soil ConservationService are presented in Exhibit Do The Service is not as active in this area as in most parts of California but has an interest in the project since agriculturallands are being protected from flood damage.

E-1 E-6. PUBLIC HEALTH SERVICE

The recommendationsof the Public Health Service are contained in their report included herein as Exhibit Eo As is the case with the Uo So Fish and Wildlife Service, the recommendationsof Public Health Service are concerned with constructionaspects of the project which will be fully considered during advanced planning stages.

SECTION III - STATE AGENCIES

E-7. STATE OF CALIFORNIA

The Department of Water Resources has consolidatedthe comments of in- terested State agencies and these are presented as Exhibit F in this appendix.

ao Department of Water Resources. The Department of Water Resources finds that the proposed plan of improvementwould have no apparent conflict with the California Water Plano The estimated land acquisition and relocation costs are questioned by the Department as is the decision not to remove the sand spit at the mouth of the stream° Land costs have beenreviewed and those presented in the report are considered adequate for this stage of project formu- lation° It is anticipated that stream velocities would effectively scour and remove the sand spit prior to occurrence of peak flood flows°

bo ~epartment of Fish and Game° The recommendations of the Department of Fish and Gameare similar to those of the Uo So Fish and Wildlife Service and will be fully considered during the advanced planning stage of the project.

co ~ivision of HiKhwayso The Division of Highways assumes thatit will be contacted by the project sponsors for permission to performnecessarywork within state-ownedrights-of-way during constructionof the project.

SECTION IV -RESOLUTIONS

E-8o SPONSORINGAGENCY

The Board of Supervisorsof Humboldt County, by letter dated 24 January 1961, gave assurances of required local cooperation° The letter is presented as Exhibit Go The cash contribution noted in item (6) of the letter will not be required under current policies of the Corps of Engineers.

E-2 UN ITED STATES PACIFIC REGION DEPARTMENT OF THE INTERIOR (REGION I} FISH AND WILDLIFE SERVlCE CALIFORNIA BUREAUOF SPORTFISHERIES AND WILDLIFE IDAHO 1001 N. E. LLOYD BLVD. MONTANA NEVADA ADDRESS ONLY THE P. O. BOX 3737 OREGON REGIONAL DIRECTOR PORTLAND 8t OREGON WASHINGTON

3 6 6 March 15, 1960 1

Colonel John S. Harnett~ District Engineer San Francisco District3 Corps of Engineers Box 3050, Rincon Annex San Francisco 19, California

My dear Colonel Harnett:

We have reviewed your plan of improvement for Redwood Creek, Humboldt County~ California. Our analysis of the effects the proposals would have on fish and wildlife is based upon data obtained from you prior to December 1959. This is our report prepared in accordance with the Fish and Wildlife CoordinationAct (48 Stat. 401, as amended; 16 U.S.C. 661 et seq. ).

Redwood Creek would be confined to the existing channel by installation of rip-rap and constructionof levees along both sides of tha stream for about one mile in the vicinity of Orick, California. T~ere would be no significant change in channel alignment although the levees would result in some constricting of the channel. Woody vegetation would be removed along the banks. Changes in the channel bed would be limited to some clean-up work between the existing banks above the existing channel grade. Snags, boulders, and flow-retardingmaterials would be removed. Levee material would not be obtained from the channel, but the channel bottom would be affected by constructionactivity.

Reservoirs on Redwood Creek for single purpose flood control and for dual purpose flood control and fishery enhancement have been investigatedbut were not found to be economicallyfeasible.

Redwood Creek flows in a northwesterlydirection through heavily forested hilly terrain in Humboldt County and enters the Pacific Ocean about ll miles south of Klamath River. Streamside vegetation in the project area is composed largely of willow thickets with some alder and cottonwood trees. The understory includls blackberry vines and forbes.

E73EB IT A Prairie Creek, the principal tributary, joins Redwood Creek at the head of the project area about & miles upstream from the ocean. Lesser upstream tributariesare short and precipitous.

Streamflow is highly variable, ranging from a minimum of lO second-feet to a flood peak of 50,000 second-feetat Orick. ~,’lean streamflowfor the period 1896 through 1947, as indicated by synthetic records developed by the California Department of Water Resources, was about 1,100 second-feet at 0rick. Usually at this point in late summer and in early fall prior to the fall ralns, strean~low is about 20 second-feet. (Based upon 6 years of record 1911-13and 1953-56.)

It is estimated that Redwood Creek presently receives average annual runs of 5,000 chinook salmon, 2~000 silver salmon, and lOgO00 steelhead trout. These spawning runs ascend the stream for a distance of at least 48 miles. The lower section of the stream and Prairie Creek support good populations of sea-run cutthroat trout. Chinook salmon and silver salmon utilize Prairie Creek and reaches of Redwood Creek for spawning. A moderate amount of chinook salmon spawning occurs in the project area. The stream section that would be affected by the project is a valuable rearing area for young steelhead and salmon. Steelhead spawn in accessible headwater areas. Fishing pressure on Prairie Creek and lower Redwood Creek is moderate.

Wildlife In the project area is varied and includes nearly all species common to northwestern California. However, only a small number of any species exist in the immediate area to be affected. Ducks, geese, and various shore birds utilize the lower stream reaches during migrations. There are moderate numbers of fur animals in the watershed. Hunting pressure on big game, waterfowl, and upland game in this drainage is light.

Levee constructionand channel modificationcould adversely affect fish habitat unless precautions are taken during the constructionperiod. Con- struction specificationsshould include provisions to preserve all pools and the low flow channel. Should portions of the low water channel be unavoidably destroyed or disrupted these sections should be restored by means of a training channel.

Small numbers of California quail and brush rabbits would be adversely affected by the removal of bank vegetation and clearing proposals. There would be minor losses of mallard and wood duck nesting habitat. Beaver, mink, raccoon3 and skunk habitat would be disturbed during the construction period, but losses to these species would be temporary and minor.

To minimize the adverse affects the project would have on fish and wildlife resources,it is recommendedthat:

1. Insofar as possible constructlon activity be limited to the period July 1 - October 31. 2. Constructionspecifications provide for preservationof the exist- ing low flow channel and pool, and that a training channel not less than 1 foot deep and 6 to l0 feet wide be installed in sections of the existing low water channel unavoidablydestroyed or disrupted.

3. Clearing specificationsprovide for preservationof riparian vegeta- tion.

During the developmentof detailed plans and specificationsand during the constructionperiod, Bureau of Sport Fisheries and Wildlife working in 3 cooperationwith California Department of Fish and Game will be pleased to 6 6 provide general advice on fish and wildlife matters related to Redwood Creek 3 project.

Sincerelyyours, UN ITED STATES DEPARTMENT OF THE INTERIOR PACIFIC REGION (REG ION | ) FISH AND WILDLIFE SERVICE CA L I FORNIA BUREAUOF SPORTFISHERIES AND WILDLIFE P IDAHO E 400! N. E. LLOYD BLVD~ MONTANA ADDRESS ONLY THE S P. O. BOX 3737 NEVADA C REG JONAL DIRECTOR A PORTLAND 8t OREGON OREGON D E WASHINGTON R September 21, 1961 0 3 6 6 5 MAIL

Colonel John A. Morrison~ District Engineer San Francisco District~ Corps of Engineers P. O. Box 3050, Rincon Annex San Francisco 19~ California

Dear Colonel Morrison:

This responds to your August 30, 1961, request for our comments on your report on Redwood Creek~ Humboldt County~ California.

Our letter report, dated March 15, 1960, based on data received from your office in December 1959~ is still to a large extent applicable to your present plan and should be included in your Appendix E together with this letter.

The plan recommendedin your report is considerablymore comprehen- sive than that considered in our March 1960 letter report. It would intensively channelize and confine by levees about 3 miles of Redwood Creak between Prairie Creek and Pacific Ocean rather than i mile. It would be more damaging to fish and wildlife. Recommendations and conclusionsof our report are only briefly mentioned in your report. We consider your discussion of the impact of the work on fish and wildlife to be inadequate.

~he following specific comments refer to paragraphs and pages of your report draft3 dated August 1961~ and its appendices:

lo Paragraph 2, p. i, and pars~raph 49~ p. 15, made no mention of the fact that fishery enhancement was amo~ the purposes fo~ which upstream reservoir constructionwas considered.

EXHIBIT ’A’ Paragraph 19, P. 6, mentions fish and wildlife but unfortunately states, "The gravels in the stream channel in the vicinity and upstream from Orick are an excellent source of aggregates." (italics ours)~ This was stated despite our March 1960 recom- mendation number (2) which recommends in part, "Construction specificationsprovide for preservationof the existing, low flow channel ....

Paragraphs 45 and 50, PP. 14 and 15, mention potential diversion @ to Skunk Cabbage Creek. Although your report rejects this pro- posal, we desire to emphasize that constructionof such a diver- sion would destroy substantialamounts of wildlife habitat and would have potential for damage to migrating fish which would be stranded in the dry channel of the lower reaches of Redwood Creek followinga flood.

~o The discussion of paragraphs 52, 54, and 55, PP- 16-18, gives no evidence of considerationof the fish and wildlife effects outlined in our report of March 1960.

Paragraph 64, p. 21, is unduly optimistic about benefits to fish . and wildlife. Your present plan calls for complete channeliza- tlon with loss of existing pools, and essentiallycomplete removal of vegetation along 3 miles of the creek near Orick. Both fish habitat and wildlife habitat will be destroyed with resultant losses to these resources as discussedin our March 1960 report. Our recommendationsnumbered (2) and (3) specificallyrequested avoidance of this type of damaging construction,yet no comment on this fact is contained in your report. Your paragraph 65, p. 21, makes no mention of these losses among the adverse project effects.

6. Paragraph 73, P- 2S, does not accurately reflect our March 1960 report, nor does it adequately treat the subject of fish and wildlife effects. Each of our specific recommendationsshould have been discussed. If our recommendationswere rejected, as appears to be the case, then an explanationshould have been given.

7. ParagraphB-11b., p. B-6 (AppendixB), mentions the gravel bars near the confluence of Prairie and Redwood Creeks as a source for sand and gravel. These bars are used by salmon for spawning. None of the gravel bars within the channel normally watered by the fall and winter flows (excluding flood peaks) should disturbed unless absolutely essential to the planned channell- zation. Borrow should be obtained entirely from channel sections

2 where excavationis required to produce the needed channel capacity, or outside the normal channels as recommendedin our March 1960 report (recommendation2). Both the low-flow channel and the pools should be preserved insofar as possible in the channelized P E section. Gravels of the stream bottom should not be removed unnecessarily,especially in the area upstream from Orick. t~ A D o ParagraphB-11c., p. B-6, again notes that materials can be E obtained from streambed deposits. In all cases, only the R deposits required to be excavated for channel rectification 0 should be removed as borrow or constructionmaterials. 3 6 6 Paragraph C-2c., p. C-3 (Appendix C), mentions the training 7 channel recommended(recommendation 2) in our March 1960 report. However, our Recommendationsnumbered (1) and (3) do not appear to have been considered among the bases for design as outlined in AppendixC.

We reemphasizethe applicabilityof our March io6c r~port to your present plan and strongly urge that our prevlousAy stated three recommendationsbe given full and carefk~; ~.on~iderationin your planning and report discussion. In a~.~ion, we request considera- tion of the following.

In addition to the three recom~ndatlonsof our March 1960 report, it is recommendedthat:

The Corps of Engineers encourage local ageneies to provide to the public foot access to the river within the project area for purposes of fishing and, where not restricted for safety reasons~ for hunting.

The Corps of Engineers place limitationsupon the project con- tractors to prevent destructionof fish and wildlife habitat. Of particular concern are spawning gravels and riparian vegeta- tion. Silt and other debris should be prevented from entering the river, gravel of the streambed should not be removed except to achieve required lowering of the channel grade, and riparian vegetationshould be preserved wherever possible.

This letter has been reviewed by Bureau of Commercial Fisheries and they concur in its content. Our comments have been discussed with California Department of Fish and Game, and that Department is in general agreement.

3 This opportunity to comment on your report is appreciated.The two advance copies of your report are attached and being returned as you requested.

Sincerelyyours,

Regional Supervisor River Basin Studies

Attachments2. AR~ONA CALIFORNIA NEVADA HAWAII U. S. DEPARTMENT OF COMMERCE BUREAU OF PUBLIC ROADS REGION~SEVEN California Division P. O. Box 1915 p 07-04 SACRAMENTO 9, CALIFORNIA E September 12, 1961 k~ A D E R District Engineer © Corps of Engineers 180 New Montgomery Street 3 6 San Francisco, California 6 9 Dear Sir :

By letter dated August 30, 1961~ you submitted for our review and comments an advance copy of your survey report for flood control and allied purposes on Redwood Creek, Humboldt County, California.

We note that Highway US-101, Federal-ald Primary Route No. I, will require raising at one location. Federal funds participated in the construction of this highway under Project FA 16B, north of Orick and FA 16(4) south or Orick.

As it is understood that your office is in contact with the California Division of Highways, the local agency directly responsible for the affected Federal-aid highway, Public Roads’ interests are satisfied.

In compliance with your request the advance copy of the report and appendices are returned herewith.

Very truly yours,

For D.~J.~ STEELE Divis ion Engineer

Enclosure

EXHIBIT B ADDRImS AM., COMMUNICATIONS TO THE REGIONAl. DIRECTOR UNITED STATES DEPARTMENTOF THE ~NTERIOR BUREAU OF RECLAMATION , P REGIONALOFFICE~ REGION 2 E 0N REPLY P. O. BOX 25t 1 S REFER TO: 2-73o C ~ACRAMENTO, CALIFORNOA A (TOWN AND COUNTRY ARF.A) D E R O 3 SEP15 1161 6 7 i

District Engineer U. S. Army Engineer District, San Francisco Corps of Engineers SauFrancisco 5, California

Dear Sir:

This is in response to your letter of August 30 (file SPNGP), requestingour review and comment on your survey report and appen- dices on Redwood Creek, Humboldt County, California.

We have reviewed your report and appendices,and the plans pre- sented donot conflict with any existing proJectsor plans of the Bureau of Reclamation.

We are returning the report as you requested~ thank you for the Opportunityto review it.

Sincerely yours,

E.F. Sullivan ActingRegional ~reetor

Enclosures 2

|, EXHIBIT C J UNITED STATES DEPARTMENT OF AGRICULTURE SOIL CONSERVATIONSERVICE

2020 l;ilviaStreet Berkeley h, California P E S September19, 1961 C A D E R 0 3 Colonel John A. Morrison, Dist~ct En{:ineer 6 S. Army Engineer District, San Francisco 7 U. 3 Corps of Engineers 180 New Montgomery Street San Francisco, California

Dear Colonel Morrison:

We have r~ceived a copy of Survey Report for i.lood Control and Allied i~rposes, Redwood Creek, ]~boldt County, California,with Appendices,which we are returning here- with. We have no adversecor~ents.

While ~le Soil ConservationService is not as active in the area as in most parts of California,we have an interest in the fact that agriculturalland and agriculturalflood damage are involved in the project. As a general principle, protectionof agriculturalland i’rom flooding facilitates the applicationof beneficialland treatment measures.

We would appreciate your placing this office and that of our Area Conservationiston the list for informationperti- nent to the project. The Area Conservationistis:

Jack E. Woods Soil ConservationService 226 South Main Street Sebastopol,California

Thank you for the opportunityto review the report. Sincerely,

John S. Barnes State Conservationist

C. H. Buell, Acting CC~ Kirk M. Sandals, SCS, Berkeley E. J. Core~ SCS, Portland, Oregon

/ / EXHIBIT D DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE REGIONAL OFFICE

P PUBLIC HEALTH SERVICE September 22, 1961 E 447 Federal Office Building S C San Francisco 2, California A D E R 0 3 6 Col. John A. Morrison 7 5 District Engineer, Corps of Engineers U. S. Army Engineer District 180 New Montgomery Street San Francisco, California

Dear Col. Morrison

As requested in your August 30, 1961 letter, enclosed please find our report on the Public Health Aspects of the Survey for Flood Control and Allied Purposes of Redwood Creek, Humboldt County, California, together with four copies of your report (Nos. 32, 34, 35, & 36) and appendices. We shall return the remaining copy (No. 33) and appendices as soon as we receive the set from the California Department of Public Health.

It is our feeling that the 20 days allotted for this report distri- bution and review were not enough. It would be appreciated, there, fore, if your office would allow a minlmumof 45 days forthe review and submittal of Public Health comments, when submitting future reports.

Sincerely yours,

~/m~-William B. Schreeder St. Sanitary Engineer Division of Water Supply & Pollution Control Region IX

Enclosures

EXHIBIT E REPORT

on P E THE PUBLIC HEALTH ASPECTS S C A of the D E R SURVEY FOR FLOOD CONTROL AND ALLIED PURPOSES O of 3 6 7 REDWOOD CREEK, HUMBOLDT COUNTY, CALIFORNIA 7 for

THE U. S. ARMY CORPS OF ENGINEERS

prepared by

THE U. S. PUBLIC HEALTH SERVICE

DEPT. OF HEALTH, EDUCATION, & WELFARE

REGION IX - SAN FRANCISCO, CALIFORNIA

September 1961

EXHIBIT E PUBLIC HEALTH ASPECTS of the SURVEY REPORT FOR FLOOD CONTROL AND ALLIED PURPOSES P E REDWOOD CREEK HUMBOLDT COUNTY, CALIFORNIA S C A D E R O INTRODUCTION 3 6 7 In accordance with the policies and procedures of the Federal Inter- 9 Agency Committee on Water Resources, this office has reviewed the Survey Report for Flood Control and Allied Purposes, Redwood Creek, Humboldt County, California, as requested by the San Francisco District of the Corps of Engineers. In preparing this report the Public Health Service has requested the comments of the California State Department of Public Health.

PROJECT DATA

Location & Description ~f ProJectArea

Redwood Creek is situated on the western slopes of the Coast Range Mountains in northwestern California. It drains an area of approximately 283 square miles located entirely in Humboldt County. The drainage basin is roughly rectangular in shape extending 56 miles along a northwest- southeast axis and having a maximum width of about seven nttles. With the exception of the lower five miles, the stream flows through a narrow deep canyon. The stream is not navigable for other than small boats. The flat valley area contains approximately 1,000 acres of agricultural lands, practically all of which are devoted to dairy farming and production of forage crops. Elevations of the drainage basin vary from sea level at the Pacific Ocean, about 50 miles south of the Oregon boundary, to 5,000 feet mean sea level at the southeastern extremity of the basin. The largest tributary is Prairie Creek which drains the northern part of the basin and joins Redwood Creek just upstream from the town of Orick. The terrain is mountainous and heavily wooded. Level land is found in small areas along the streams. The only significant area of level land is along the lower four miles of the stream, where the town of Orlck is located. Practicallyall the areas suitable for agriculturein the Redwood Creek basin are located within the proposed project limits, The problem area ~s the flood plain and channel of the lower four miles ofRedwood Creek~ starting approximately from the confluence with Prairie Creek downstream. Agricultural activities are devoted mainly to the dairy industry. Much of the commercial and industrial activities are dependent upon the lumber industry. Developments in the area include the town of Orick, about five sawmills, one large logging pond, and about 1,000 acres of relatively flat agricultural lands.

Problems of the Area

The north-coastal streams of California along the ocean are in areas of high rainfall and flooding is almost an annual occurrence. Due to the long, narrow shape of Redwood Creek basin and the limited area of economic development, the flood problem generally is confined to the town of Orlck and vicinity. In the last 10 years, two major floods along Redwood Creek have severely damaged the community and adjoining farm lands throughout the lower four miles of the stream. The floods of 1953 and 1955 inundated portions of Orlck to depths of four feet, and damages from the more severe of the two, that of 1953, are estimated at about $1,230,000, adjusted to April 1960 price levels and developments. The small valley, with limited area for development and production, is an important factor to the local lumber industry. The degree of economlc development in the community and the cost involved in complete abandonment of the floodplain is not considered practicable or feasible.

Proposed Plan of Improvement

The plan of improvement considered most feasible for resolving the flood problem of Redwood Creek includes construction of earth levees and channel improvements along the lower four miles of the stream. The workwould consist of channel rectification, levees, and partial revetment. A trapezoidal-type channel would be used through the urban and downstream rural areas and a system of s~back levees with an improved channel upstream from the mouth of Prairie Creek.

Zn order to assure adequate interior drainage of local runoff from behind the levee system, a battery of gated culverts through the levee would be provided to prevent flow onto protected areas during high flood stage. A pumping plant would be installed near this drainage facility to remove floodwaters which collect behind the levee when the flapgates are closed due to high water in the stream.

Water Supply

This plan for watershed protection does not contemplate divertingwater for beneficial use. To our knowledge, the proposed plan in no way conflicts with measures in the State of California Water Plan or with existing potable ~ater supplies.

Water Pollution Control

Provisions for debris retention in the flood water retention structures

-2- and concrete lining of the drainage channels will be of general benefit in protectlnglsewage disposal facilities and subsequently the spread of polluted flood waters.

General P Sanitation E S Measures should be incorporated in the work plan to protect the channels C A from belng used as trash dumps and open sewers. All construction camps D and temporary facilities should be in accordance with local health regula- E R tions regarding water supplies and sewage disposal facilities. Inspection 0 of the works of improvement is desirable in the fall and spring, in addi- tion to after each major flood, in order to determine what maintenance 3 6 activities are required. 8 1 VECTOR PROBLEMS

Public Health and Soelo-Economlc Importance

Mosquitoes are the principal vectors which might be affected by the project. Several species of mosquitoes of public health importance may be produced in large numbers in the area when suitable aquatic habitats are present. Encephalltls, commonly known as sleeping sickness or brain fever, is now the most important mosqulto-borne disease in the United States and this area. Mosquitoes transmit the encephalitis viruses among birds and from them to horses and humans. There are no effective chemotherapeutic measures for preventing or treating human cases, and some individuals, particularly children, who recover from encephalltls, often suffer perm- anent mental disability.

Records of the U. S. Department of Agrlculture show that equine encepha- litis cases occurred in Humboldt County during 8 years of the 17-year period, 1939 through 1955, for which records are available. These records of equine encephalitis cases indicate that the viruses of the disease occur in the area. Culex tarsalls, the encephalitis mosquito, is common to the area of the proposed projlct. It is produced in a wtdl range of aquatic habitats, such as roadside ditches, seepage pools, flooded depressions, and other semipermanent and permanent bodies of water which contain emergent vegetation.

Several species of vlcious-bitlng Aedes mosquitoes, including A. dorsalls, A. ni~romaculis, and A. ~ncrepituss are prevalent in the area. Large numbers of these biting mosquitoes may create publlc health problems aside from the transmission of specific diseases. These insects may interfere with the healthful outdoor activities of both children and adults durlngthe summer months. Individuals, particularly children, " frequently require medical attention and sometimes hospltallzatlon for treatment of secondary infections and allergic reactions resultlng from mosquito bites. Overflow pools along streams provide favorable larval

-3- habitat for several species of the highly pestiferous Aedes mosquitoes.

In addition to their public health importance, large numbers of biting mosquitoes also cause severe economic losses by lowering meat and milk production, by reducing the efficiency of agricultural and industrial workers, by interfering with recreational enterprises, and by lowerlng the value of real estate.

Anticipated Effects of the Project on Vector Problems

The project is expected to result in reduced flood damages sustained by the town of Orlck, several lumber mills, and most of I000 acres of agricultural area. The over-all effects of the project should there- fore be beneficial from a mosquito control standpoint. Mosquito production may occur in the channel and behind levees If any of the gated culverts and other drainage facilltles become clogged and water is ponded for periods of 5 days or longer. The aquatic stages of mosquitoes generally occur in shallow water with abundant vegetation and flotage and where they are protected from wave action and water currents; they do not occur in the deep open waters of streams, ponds, and lakes.

Mosquito production can be prevented or minimized if adequate preventive and control measures are planned and built into the project and continued as a part of the regular operation.

RECOMMENDATIONS

Responsibility for Vector Control

Responsibility for vector prevention and control is normally associated with land ownership or operating rights. The agency, group, or individuals responsible for various aspects Of the proposed project should therefore be prepared to accept full responslbillty for the prevention and control of mosquitoes and other vector problems resulting from the design, construction, operation, or maintenance of the project.

Prevention and Control Measures

In order to minimize public health hazards, every possible effort should be made to avoid creating mannmde conditions whichwill increase populations of mosquitoes and other aquatic arthropods of public health importance. It is recommended that the following principles and practices be adhered to in the design, construction, operation, and maintenance of the proposed project:

4m. Lateral drainage should be built and maintainedfor all potentialpondlng areas resulting from channel improvements and constructionof levees.

2. Culverts, inlets, underdralns,etc., should be placed on grade to insure complete drainage° P E S o If permanent ponding areas are anticipated,steep side C A slopes should be provided for these ponds and emergent D vegetation should be controlledperiodically by mechanlcal, E or biologicalmeasures° R chemical, O 4. By-passed natural drainagewaysshould be filled in and graded 3 ~6 to insure complete lateral drainage into the new channel. .8 -~3 5. Borrow areas should be left in a self-dralnlngcondition.

Water should be pumped or otherwise removed from pondlng 0 areas behind levees as rapidly as possible, preferably within 5 to 7 days.

Provisions should be made for periodic removal of debris, . silt, and vegetation from drains and channels to insure free flows.

SupplementalChemical Control Measures

In situations where adequate control of mosquitoesis not obtained through the prevention and source reductionmeasures outllned above, provision should be made for supplementaryuse of insecticides to achieve the desired level of control.

Technical Assistance \ In the event that vector controls are encountered in the proposed project technical assistance may be obtained from the California State Depart~nentof Public Health and the U. S. Public Health Service.

Accident Prevention

Generally, the reduced flood danger should lead to a safer environment. However, the following additions to the planned facilities are recommended:

1. Channels should be fenced through residential areas and should be so designed as to prevent public access, insofar as feaslble°

-5- WarnlnE signs should be placed at all danEerous facilltles and at suitable points on canals to advertise to the public the danser of flash floods.

General

It is further recommended that the California State Department of Public Health and the U. S. Public Health Service be kept currently informed reEardlnE any chanEes in plans, so that guidance and consultation may be provided with regard to health problems associated with the project. EDMUND G. BROWN WILLIAM £. WARNE GOVERNOR ADDRESS REPLY TO DIRECTOR P. O. BOX 388 SAGRAMENTO Z llSO N STREET HI CKORYS-47|1

P E S STATE OF CALIFORNIA C A D eparlmet of Nateresour es E R SACRAMENTO 0 $EP2 7 1961

Colonel John A. Morrison District Engineer U. S. Army Engineer District Corps of Engineers San Francisco 15, California

Subject: Your File No. SPKGP

Dear Colonel Morrison:

This is in reply to your letter of August 30, 1961, which transmittedcopies of your "Survey Report of Flood Control and Allied Purposes, Redwood Creek, Humboldt County, California",dated August 1961, for review and comment by interested state agencies°

The following comments of state agencies concerned are sub- mltted for your consideration.For the sake of brevity, your survey report will be referred to as the "Redwood Creek Report".

DEPARTMENT OF WATER ~ESOURCES

The Department of Water Resources has a direct interest in all projects involvingthe develolmuentof water resourceswithin the State. Of particular interest is the extent to which these projects are compat- ible with the State’s comprehensiveplan for the developmentof the water resourcesof California.

With regard to projects involving ~1ood control, the department has a financial interest in accordance with policies set forth in the State Water Resources Law of 1945 and the Flood Control Fund Law of 1946, under which the State is authorized to reimburse local agencies for the cost of lands, e~sements, and rights of way required for channel improvementsof federal flood control projects.

Plan of Im?rovement

The Redwood Creek Report presents a plan of flood control for tthe lower reaches of Redwood Creek, in and about the community of Orick

EXHIBTT F Colonel John A. Morrison -2- in Humboldt County, California. The plan proposes channel rectification, levees and revetment ~long the lower four miles of Redwood Creek. Interior drainage would be provided by a battery of gated culverts through the levee, and a pumping plant installed near this drainage facility to remove collected flood waters when the flapgates were closed.

The project would produce average annual benefits of $228,000. Annual cost of the project is listed as $129,000, and the ratio of benefits to cost is 1.77 to 1.O0. Total first cost of the project would be $2,850,000. The annual non-federal cost for operation and maintenance would be $19,500, which would be borne by local interests.

Design discharge for the standard project flood is 77,000 second- feet. The improved channel would vary in dimension, but would have a minimum bottom width of 250 feet.

The California Water Plan

The proposed plan of development would have no apparent conflict with The California Water Plan.

1~drology

The standard project flood of 77,000second-feet appears to be reasonable. However, using the same flood frequency of one in 30-years, computations by the department indicate that the pumping plant for~interior drainage should be redesigned to accommodate 338 second-feet in contrast to a design capacity of 143 second-feet as outl~n the report. II Right of Way and Relocation Estimates

Upon review of the rights of way costs as outlined in the Redwood Creek Report, the following is concluded:

i. The land acquisition and relocation costs as outlined in the report appear to be low by approximately $120,000. Adjustment of the benefit-cost ratio to accommodate this increase of expected expenses results in a ratio of 1.56 to l, in contrast with a value of 1.77 to 1 derived in the survey report.

In order to lower land acquisition and relocation costs . mentioned above, consideration should be given to keeping the flood channel upstream from the 0rick Bridge as far to the left as possible, thus avoiding any construction in the urbanized area on the right bank.

Design; Construction and Cost Estimates

The survey report leaves some doubt as to whether the mouth of Redwood~ Creek would remainopen should a sand spit form there as at present. If the mouth tended to fill in, there should be an adequate item for dredging in the annual operation and maintenance costs. The Colonel John A. Morrison -3-

possibilityalso exists that the spoiling of waste excavation in the aban- doned channel would fill in portions of the channel, thus creating new land. No benefit was claimed for this land, and no mention was made ofits P disposal. E S C A DEPAR~.~NT OF FISH AND GA~ D E The Department of Fish and Game recommends that the following be R O adhered to in order to keep d~mage to fish and wildlife resources within acceptablelimits: 3 6 8 1. To permit the ~assage of salmon and steelhead into 7 Redwood Creek during low flows, the channel at the lower end of the project should be modified to concentratethe flow.

o To avoid the destructionof salmon spa~ming areas, gravel should not be removed from areas normally watered by fall and winter flows (excluding peak flows)° Borrow should obtained only from channel sections required to produce needed channel capacity°

To assure the upstream passage of anadromous fishes during low flows, certain channel modificationswould be required. These modifications,such as spaced resting pools, would be in addition to the six by one foot fish channel described in the report.

4. Riparian vegetation should be preserved wherever possible.

Since the final plans for channel ~mrk would be affected by the foregoing recommendations;it is recommendedthat the Corps of Engineers request the assistance of technical fisheries personnel of the U. S. Fish and Wildlife Service and/or the California Department of Fish and Game. Further, technical personnel of these agencies should be available for review of project operationduring construction.

DEPARTMENT OF NATURAL RESOURCES

The Department of Natural Resources reviewed the survey report but had no comments.

DIVISION OF HIGHWAYS It is noted by the Division of Highways that the proposed levees cross U. S Highway lO1 at the Orick Bridge in the vicinity of levee station 163 + 00. It is assumed that the project sponsors will contact the District I office of the Division of Highways in Eureka for permission to perform necessary work within state-owned rights of way. It is also assumed bhat the sponsors will make arrangementsfor possible grade revision to the highway required by levee constructionnear station 163 + 00. Colonel John A. Morrison

CONCLUSI0i~S

On the basis of the review of the Redwood Creek Report, it is concluded that:

i. The Redwood Creek Project~ as outlined in the Survey Report, would not conflict with The California Water Plan.

2. The pumping plant for interior drainage should be redesigned to accommodate 338 second-feet~ in contrast to a design capacity of 143 second-feet as outlined in the report.

The estimates of flood control benefits appear reason- Q able.

4~ The land acquisition and relocation costs appear low by approximately $120,000 and should be reviewed.

Insofar as practical and consistent with the basic . aims of the project, the following recommendations of the Department of Fish and Game should be followed:

(a)The lower end of the project should be channelized in order to permit the passage of salmon and steelhead at low flows.

(b)To avoid the destruction of salmon spawn- ing areas, gravel should not be removed from areas normally watered by fall and winter flows (excluding flood peaks). Borrow should be obtained only from channel sections required to be excavated to produce needed channel capacity.

(c)To assure the upstream passage of anadromous fishes during low flows, certain channel modifications would be required. These modifications, such as spaced resting pools, would be in addition to the six by one foot fish channel described in the survey report.

(d)Riparian vegetation should be preserved when’ ever possible.

(e)Since final plans for channel work would be affected by the foregoing recommendations, it is recommended that the Corps of Engineers request the assistance of technical fisheries personnel of the U. S. Fish and Wildlife Service Colonel John A. Morrison -5-

and/or the CaliforniaDepartmentof Fish and G~neo Further, technical personnel of these agencies should be available for review of project operation during construction.

The Corps of Engineers should contact the Division of Highways, District I Office, in Eureka in order to coordinate planning problems in connection with state-o~nedrights of way and grade 3 revision of U. S. Highway lOlo 6 8 9 The foregoing comments are subject to such revision as may be con- sidered advisable upon official receipt by the State of California of the report of the Chief of Engineers. The opportunity to review the report is very much appreciated.

Sincerelyyours,

Director 9TATE OF CALIFORNIA COUNTY OF HUMBOLDT BDARD OF SUPERVISORS VETERANS ~ MEMORIAL BUILDING P. 0, BOX 1014 E:UREKAo CALiFORNiA PHONE HI LLBID£ 3-0811 AREA CODE 415

JA:~.rUARY24, I~I.Uo

DISTRICT ENGINEER IJ. S. ARMY ENGINEER DISTRICTp SAF’,.t FRAMCISCO QORPS OF ~NGINEERS SOX 30.50, ’."2., INCOF~ANNEX SAH FRANC ISCO 19, CALIFORNIA

D~:AR S I R "

REFERENCE IS [,.,’lADE TO YOUR LETTER OF 19 OCTOBER1960 COP,,!(:ERN- ING A PROPOSED FLOOD CONTROL PROJ_CT ON ~EDWOOD CREEK II’J THE COMMUNITY OF ORICK., AT THE PUBLIC HEARINGS HELD 10 OCTOBER 1960, THE COMMUNITY OF 0RICK MOST UNANIMOUSLY EXPRESSED ITS APPROVAl_ OF THE PROJECT., THE ~OARD OF SUPERVISORS HAS D IS~CUSSED THE MATTER AND HAS AUTHORIZED ME AS THE CHAI RL/IAN OF THE ~OARD OF SUPERVISORS TO COMMUNICATE TO THE CORPS OF -r"NGII~JEERS THE COUNTYVS WILLING- NESS TO INSURE THE LOCAL COOPERAT O[,,I REQUIRED BY THE CORPS OF ENGINEERS, NAMELY:

(1) TO PROVIDE WITHOUT COST TO THE UNITED STATES ALL LANDS, EASEMENTS, AND RIGHTS OF WAY FOR THE CONSTRUCTION OF WORKS.

(2) To HOLD AND .SAVE THE UN TED STATES FREE FROM DAMAGES DUE TO THE CONSTRUCTION WORKS.

(3) To MAINTAIN AND OPERATE ALL THE WORKS AFTER COMPLE- TION IN ACCORDANCE WITH REGULATIONS PRESCRIBED BY THE SECRETARY OF I’HE ARMY,

(4) To PROVIDE WITHOUT COST TO THE UNITED STATES ALL RE- LOCATIONS OF BUILDINGS, ROADS~, AND UTILITIES REQUIRED BY THE PROJECT.

(,.5) PROVIDE ASSURANCE THAT ENCROACHMENT ON IMPROVED CHAN- NELS, OR ON PONDING AREAS, WILL NOT BE PERMITTED.

PROVIDE A CASH CONTRIBU-FIOr,,I IN VIEW OF SPECIAL BENEFITS.

Exhibit G ii

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© .._22-_ [,! 12_ C CO co cL n- O "T- O O P SPDGP (Aug 61) Ist Ind E SUBJECTs Report of Survey on Redwood Creek, Humboldt County, for Flood S C Control and Allied Purposes A D E U S Army Engr Div, South Pacific, San Francisco, Calif 26 September 1961 R O TO: Chief of Engineers, DA, Washington, Do C~ 3 .6 I concur in the conclusionsand recommendationof the District 9 3 Engineero

Colonel,C,erps Division Engineer

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