LIBRARY UNIVERSITY OF CALIFORNIA DAVIS CCP>^ 2 THE RESOURCES AGENCY OF CALIFORNIA Department of Wa ter Resources Bulletin No. 109 COLUSA BASIN INVESTIGATION Preliminary Edition JUNE 1962 EDMUND G. BROWN Governor State of California WILLIAM E. WARNE Administrator The Resources Agency of California and Director Deportment of Water Resources state of California THE RESOURCES AGENCY OF CALIFORNIA Department of Wa ter Resources Bulletin No. 109 COLUSA BASIN INVESTIGATION Preliminary Edition JUNE 1962 EDMUND G. BROWN WILLIAM E. WARNE Governor Adminisfrator State of California The Resources Agency of California and Director Department of Water Resources jstm^* The bottleneck of Colusa Basin drainage where ihe Knighfs Landing Ridge Cut n)eeti the Yolo Bypass. Only two small channels (center foreground and at left adjoining road) are available for controlled release of drainage flows. TABLE OF CONTENTS Page LETTER OF TR/mSMITTAL x ACKNOWLEDGEMENT xi ORGANIZATION, DEPARTMENT OF WATER RESOURCES xii ORGANIZATION, CALIFORNIA WATER COMMISSION xiii CHAPTER I. INTRODUCTION 1 Authorization for Investigation 1 Objective and Scope of the Investigation . 3 Preliminary Reconnaissemce 3 Extent of Problems Studied k Extent of Area Studied h Possible Solutions 5 Levee Protection 5 Flood Control Reservoirs 6 Watershed Management 6 Improved Drainage 7 Engineering and Economic Studies 7 Related Investigations and Reports 8 Organization of Report 9 CHAPTER II. GEOGRAPHY AND ECONOMY 11 Area of Investigation 11 Colusa Basin 12 Colusa Basin Drainage Area 13 Topography and Geology 1^ 111 Page Soils 15 Climate 1? Population l8 Reclsination 19 Sacramento River Flood Control Project 20 Works Constructed by Local Districts 22 fU.ver Levee 22 Back Levee 23 Knights Landing Ridge Cut 2k Colusa Basin Drainage Canal 2U Agricultural Developnent 29 Irrigation Works 29 Irrigation District Developments 30 Private Inrigation Developnent 33 Proposed Irrigation Develonnent 33 Water Quality 3^^ Fish and Game ^ CHAPTER III. EXISTING AND POTENTIAL FLOOD AND DRAINAGE PROBLEMS hi Existing Flood Problems k2 Existing Drainage Problems k2 Potential Flood and Drainage Problems U9 Construction of Major Works Outside the Project Area h9 Improvement of the Channels Tributary to the Drainage CeLnal 31 Cheuiges in Land Use in Colusa Basin Drainage Area 52 iv Page Flood Analyses 53 Frequency and Degree of Flooding 53 Characteristics of KLood Hydrographs 55 Annual Distribution of Floods 56 Extent of Flooding 58 Flood Damages . 58 Crop Damage 60 Miscellajieous Damage 63 CHAPTER IV. POSSIBLE SOLUTIONS 69 Colusa Basin Levee Projects 70 Estimated Costs 7^ Project Benefits 75 Crop Damage Reductions 78 Miscellaneous Damage Reductions 80 Enhancement to Agricultural Lands 82 Enhancement to Urban Lands 82 Economic Justification &i- Foothill Reservoir Project 85 Watershed Management 90 Yolo Bypass Project 92 Check Struct\ire (No. l) 93 Nev Channel 93 Enlarged Tule Canal 9!^ Check Structvire (No. 2) 98 Page Estimated Costs 98 Project Benefits 100 Economic Jxistification IO3 CHAPTER V. CONCLUSIONS AND RECOMMENIATIONS IO7 Conclusions IO7 Reccmnendatlons Ill TABLES Table Number 1 Population Data and Projections I8 2 Principal Water Users in the Colusa Basin in 1959 31 3 Flows in Colusa Basin Drainage Canal at Highway 20 Bridge k^ k Annual Distribution of Floods in Reaches 3, k, and 5 57 5 Annual Distribution of Floods in Reaches 1 and 2 57 6 Estimated Crop Damage Resulting from flooding in Reaches 1, 2, 3, k, and 5 61 7 Present and Estimated Future Crop Pattern Without Additional Flood Protection in Reaches 1, 2, 3^ ^f and 5 6h 8 Flood Conditions and Present Flood Damage in Reaches 2, 3, ^, and 5 ^ 9 Channel Widths and Design Discharges for Col\isa Basin Levee Projects 72 Table Number Page 10 Estimated Capital Costs of Colusa Basin Levee Projects 76 11 Estimated Annual Costs of Colusa Basin Levee Projects 77 12 Estimated Annual Benefits of Colxisa Beisin Levee Projects 80 13 Comparison of Estimated Costs and Benefits of Colusa Basin Levee Projects 85 llf Summary of Foothill Reservoir Project 87 15 Probable Discharge in Willow Creek and the Colusa Basin Drainage Canal During a Once- In- 50- Year Flood 88 16 Probable Flooded Areas in Reaches 2, 3> 1+, 5, and 6 During a Once-In-50-Year Flood 88 17 Estimated Capital and Annual Costs of Yolo Bypass Project 99 18 Duration of Flooding in Reach 2 101 ILLUSTRATIONS Photograph Number Junction of fiiights Landing Ridge Cut and Yolo Bypass Frontispiece 1 Western Foothills of Colusa Basin Drainage Area I6 2 Knights Landing Outfall Gates 25 3 Colusa Basin Dr-ainage Canal 27 U Pumping Plant at Eldorado Bend 28 5 Irrigation Instal lation on Feeder Canal of Colusa Basin Drainage Canal 32 6 Ground Water Pumping Installation 32 vii Photograph Number Page 7 Waterfowl in Coliisa Basin 36 8 Typical Rice Field hh 9 Private Levee along Colusa Basin Drainage Canal '^•6 10 Knights Landing Ridge Cut at the Yolo Bypass ^8 11 Flooding of Yolo Bypass from Knights Landing Ridge Cut ^Q 12 Tule Canal at Vicinity of Highway 20 Crossing 95 13 Tule Canal at Vicinity of Sacramento Bypass $6 FIGURES Figure Number 1 Generalized Geologic Section Across Colusa Basin ^ear Grimes !*<• 2 Pacific Migratory Waterfowl Flyway, Showing Principal Fall Migration Routes 37 3 Frequency of Flooding in Reaches 3, k, and 5 5^ k Frequency of Flooding in Reawihes 1 suid 2 55 5 Probability of Flooding in Colusa Basin and Yolo Bypass 59 6 Probability of Crop Damages in Reaches 2, 3, 1^, and 5 65 7 Probability of Miscellaneous Damages in Reaches 2, 3, h, and 5 67 vlii Figure Nxmiber Page 8 Probability of Flooding in Colxisa Basin With and Without the Colusa Basin Levee Projects 79 9 Probability of Crop Damages in Reaches 2, 3, 1+, and 5 With and Without Colusa Basin Levee Projects 8l 10 Probability of Miscellaneoxis Damages in Reaches 2, 3, \, and 5 With and Without Colusa Basin Levee Projects 83 11 Probability of Flooding (April 1 through September 30) in Reach 1, the Northern Yolo Bypass, With and Without Yolo Bypass Project 102 12 Probability of Flooding in Reach 2, Knights Landing to College City^With and Without Yolo Bypass Project 102 13 Probability of Flood Damage With and Without Yolo Bypass Project 10l4- PLATES (Plates are botuad at end of report) Plate Number 1 Existing and Possible KLood Control and Drainage Feat tires 2 Irrigated and Irrigable Lands, I95I4-56 3 Principal Irrigation Water Service Agencies and Proposed Water Service Areas \ Reclamation ajid Levee Districts 5 Profile and Typical Sections of Col\isa Basin Levee Projects 6 Profile, Plan, and Typical Sections of Yolo Bypass Project Ix WILLIAM E. WARNE Director of Woter Resources B. ABBOTT GOLDBERG Chief Deputy Director REGINALD C. PRICE Deputy Director Policy NEELY GARDNER Deputy Director Peputy Direct) Aaministrotio ALFRED R. GOLZE Chief Engineer EDMUND G. BROWN GOVERNOR OF CALIFORNIA WILLIAM E. WARNE ADMINISTRATOR RESOURCES AGENCY ADDRESS REPL P. O. Box 388 Socrcmento 2, THE RESOURCES AGENCY OF CALIFORNIA DEPARTMENT OF WATER RESOURCES 1120 N STREET, SACRAMENTO June 12, 1962 Honor«,ble Edmimd G. Brown, Governor, and Members of the Legislature of the State of California Gentlemen: I have the honor to transmit herewith the preliminary edition of Bulletin No. 109, "Colusa Basin Investigation." This bulletin summarizes the Investigation authorized by the Legislature in 1959 hy Senate Concurrent Resolution No. 79. Bulletin No. IO9 presents findings and conclusions as to the engineering feasibility and economic justification of providing Improved drainage and additional flood protection for the Colusa Basin. The solutions investigated include plans for both localized and basin-wide improvements. Sincerely yours. Director ACKNOWLEDGEMENT During the course of this investigation, valuable assistsince and data were contributed by many agencies. The Department of Water Resources gratefully acknowledges the cooperation of the following agencies: Bureau of Reclamation, United States Department of the Interior Corps of Engineers, United States Department of the Army Soil Conservation Service, United States Department of Agriculture California Department of Fish and Game California Reclamation Board California Division of Highways University of California at Berkeley and at Davis The Counties of Colusa, Glenn, and Yolo Glenn-Colusa Irrigation District Reclamation District I5OO Laugenour & Meikle, Civil Engineers, Woodland, California Blackie & Wood, Civil Engineers, San Francisco, California Special mention is made of the helpful cooperation of the many private individuals who contributed damage data of great value in the evaluation of project benefits. xi STATE OF CALIFORNIA THE RESOURCES AGENCY OF CALIFORNIA DEPARTMENT OF WATER RESOURCES EDMUND G. BROWN, Governor WILLIAM E. WARNE, Administrator, The Resources Agency of California and Director, Department of Water Resources ALFRED R. GOLZE, Chief Engineer JOHN R. TEERINK, Assistant Chief Engineer NORTHERN BRANCH John M. Haley- John W. Keysor Branch Chief Chief, Planning Section The investigation leading to this report was conducted under the direction of Stuart T. IVle Richard E. Slyfield Denzil M. Carr Joseph N. Soderstrand Armando L. Raimundo ^ Senior Engineer Senior Engineer Associate Engineer Associate Engineer Water Resources Technician I xii CALIFORNIA WATER COMMISSI(»i RALPH M. BRODY, Chairman, Fresno WILLIAM H. JENNINGS, Vice Chaiman, La Mesa JOm W. BRYANT, Riverside JOHN P. BUNKER, Gustine IRA J. CHRISMAN, Visalia GEORGE C. FLEHARTY, Fresno MARICW R. WALKER, Ventura JOHN J. KING, Petaluma NORRIS POULSON, Los Angeles WILLIAM M. CARAH Executive Secretary GEORGE B. GLEASON Principal Engineer xiii CHAPTER I. INTRODUCTIO?! The Colusa Basin is a leading eigricultural area as well as one of the most notable vaterfovl hunting areas in the State. It is located in the Sacramento Valley along the west side of the Sacramento River and extends from Stony Creek on the north to Cache Creek on the south. In the eeirly part of its history, the Colusa Basin produced mainly dry-farmed grain. The area has been progressively developed for irrigated agriculture and is presently a major producer of rice. Several reclamation districts have been formed. An extensive system of levees has been constructed along the Sacramento River and along the various drainage channels to protect the basin from inundation by floods of the Sacramento River each winter. The levees, however, have not solved local problems of shallow flooding of large areas of the basin. During the winter months, runoff from tributary drainage areas backs up behind the levees and along inadequate drainage channels. Such flooding damages fall planted crops. During the late spring months, similar problems of flooding result from return flow from irrigation practices. Authorization for Investigation Interested individxials on several occasions have met with repre- sentatives of the Department of Water Resources to discuss the current drainage and flood problems in the Colusa Basin. The Legislature became interested in the problems and, in 1959> passed Senate Concurrent Resolution No. 79 requesting the department to make a study of the problems of flooding and drainage in the Colusa Basin. This resolution reads as follows: SENATE CONCURRENT RESOLUTION NO. 79— RELATING TO A STUDY OF THE "COLUSA BASIN." "\i/HEREAS, There exists in the Counties of Glenn, Colusa, and Yolo inadequate drainage and flood control facilities that are necessary for the generaJ. area located therein which is known as the 'Colusa Basin'; and "WHEREAS, This condition of inadequate drainage and flood control has annually resulted in great dam- age to the agricultural crops in the area amounting to many thousands of dollars each yeajr; and "WHEREAS, The agricultural and economic development of the area is greatly impeded by these conditions; and "WHEREAS, The creation of new irrigation and soil conservation districts in this axea will compound the damages now being suffered; and "WHEREIAS, It is necessary for an overall plan to be developed for this area to alleviate the damages caused by drainage, seepage and storm water disposal, giving due consideration to the established water rights exist- ing in the area; now, therefore, be it "Resolved by the Senate of the State of CsLlifornia, the Assembly thereof concurring, That the Department of Water Resources is hereby requested to maJce a comprehen- sive study of the 'Colusa Basin' for the purpose of determining the best manner for alleviating the problems resulting from inadequate drainage and flood control facilities, seepage and storm water disposal giving due consideration to the protection of established water rights in the area; and be it further "Resolved, that the Secretary of the Senate is directed to transmit a copy of this resolution to the Department of Water Resources." To support the study directed by SCR No. 19, the Legislature added $80,000 to the Department of Water Resources 1959-60 Budget (item 262.5) to be spent during the 1959-60 and I96O-6I fisceil years. Objective and Scope of the Investigation The general objective of the Colusa Basin Drainage Investigation was to develop the information requested in Senate Concurrent Resolution No. 79- This objective was achieved by conducting engineering and economic studies directed toward the formulation of a plan for alleviating the drainage and flooding problems in the Colusa Basin. Preliminary Reconnaissance In order to comply with the legislative directive "... to make a comprehensive study of the 'Colusa Basin' for the purpose of determining the best manner for alleviating the problems resulting from inadequate drainage and flood control facilities, seepage and storm water disposal, giving due consideration to the protection of established water rights in the area", the first step by the Department of Water Resources was to make a rapid reconnaissance survey of the problems of the area. Information was assembled pertaining to the geography of the basin, existing flood control and drainage works, the hydrology of flooding, and, most important, the identification of areas subject to flood damages. This latter infor- mation came from interviews with residents and landowners. The reconnaissance survey indicated that the Colusa Basin appears to be adequately protected from floods of the Sacramento River, v^ich, in the past, were the major threats. To some extent, floods originating from local runoff have been controlled, although the areas not presently protected by levees continue to suffer frequent damage from floods of a local nature. Inadequate drainage of irrigation retiorn flows at certain periods of the year causes damage to crops planted earlier in the year. -3- The areas presently subject to such flooding are located along Willow Creek and along a 50-mile reach of the Colusa Basin Drainage Canal. The maximum areas flooded in recent years, as indicated on Plate 1, "Existing and Possible Flood Control and Drainage Features", include approximately 100,000 acres. The preliminary survey indicated that inadequate drainage of irrigation return flows during summer months is the most serious problem in the southern reaches, while winter flooding is the most serioiis problem in the northern reaches. Extent of Problems Studied The scope of studies conducted during the subsequent two-year investigation was limited to seeking solutions for existing drainage and flood control problems v;ith consideration of the effect of probable future develop- ment. Primary consideration was given to engineering improvements to the master drainage facilities. The problems on tributary channels and of farm drainage were considered only in their relationship to the major facilities. Consideration of individual farm drainage was not within the scope of this investigation. A reconnaissance level study was made of fish and wildlife in the area of Colusa Basin subject to flooding. Particular attention was given to migratory waterfowl, because the waterfowl habitat is dependent upon natural flooding. A more intensive study than was made would be re- quired to determine the effects that construction of levees and flood control works in the Colusa Basin would have on waterfowl. Extent of Area Studied The Eirea to which studies within the Colusa Basin were confined was determined during the initistl reconnaissance. At that time the U. S. Corps of Engineers was engaged in study of flood control on the upper reaches of Willow Creek and its tributaries. Although a small project was found economically justified in that area, public hearings indicated that local interests were unwilling to assume the operation and maintenance require- ments necessEiry to obtain state and federal financial participation. On December 23, I96O, the Corps of Engineers reclassified this project to an inactive status. Accordingly, no works were considered for the area affected by the Corps of Engineers ' study. Within the main body of the Colusa Basin, studies were confined to the area flooded in recent years. At the southern extremity of the Colusa Basin Drainage Canal, drainage problems associated with the canal extend into the Yolo Bypass. Therefore, the study area was extended south in the Yolo Bypass to the Sacramento Deep Water Ship Channel. Possible Solutions To comply with the objectives of the investigation, several alternative solutions to the existing problems of flooding and inadequate drainage were considered. These were: (l) systems of levees to protect areas subject to damage; (2) flood control reservoirs in the western foot- hills; (3) watershed management to reduce runoff rates; and (k) improve- ment and enlargement of existing drainage facilities. These approaches to a satisfactory solution are discussed in the following paragraphs with an indication of the results that may be expected for each alternative and the emphasis placed on analysis of each possible solution. Levee Protection. Levee projects of several sizes providing substantial flood control protection to the presently flooded areas of the Colusa Basin were thoroxighly investigated and found to be physically feasible. All engineering and economic factors needed to determine the economic justification of these projects were analyzed. A major portion of the work involved in this investigation was directed toward this phase. -5- Tlie largest levee system studied would provide protection from floods reaching the magnitude of that expected to occur once-in-50-years. Evaluation of the benefits provided by this project shoved an extremely unfavorable benefit-cost ratio. Annual costs vould exceed annual benefits by approximately 3 to 1. Consideration was given to providing a lesser amount of protection by reducing the size of the levee system. If protec- tion from floods expected to occur once-in-ten-years was provided, costs would exceed benefits by approximately 2 to 1. For the present level of development in the Colusa Basin, therefore, a levee project would not be economically justified. Flood Control Reservoirs. About 80 percent of a flood entering the Colusa Basin is contributed by 17 streams draining the foothills to the west. The cost of constructing flood control reservoirs on these streams was estimated and found to exceed that of a levee system. Further- more, the resei^oirs could provide a reduction only of about 50 percent in the area flooded as compared to the once-in-50-year levee protection project discussed above. Any flood control reservoir project, therefore, would require a supplemental levee system and be more costly than a levee system alone. Designs and cost estimates were prepared at a reconnaissance engineering level, and the results did not indicate that more detailed work would be warranted. Watershed Management. A brief investigation was made into the feasibility of limiting flood flows by improved watershed management. With proper watershed treatment, some reduction in flood flows could be expected; but it is considered highly improbable that, by watershed protection measures, adequate control of flood waters could be realized. The investi- gation of watershed management was quite limited in scope and, because of -6- the complexities involved, would require an extensive analysis to evaluate fully its potential. Improved Drainage. The construction of improved drainage facilities from the mouth of the Knights Landing Ridge Cut through the Yolo Bypass vas found to provide a limited degree of protection to lands at the southerly end of the Colusa Basin and within the upper portion of the Yolo Bypass. This project, designated the Yolo Bypass Project, woiild provide benefits approximately 3^ percent greater than its cost. Although the drainage project is economically justifiable, it provides only a very limited amount of protection to the lands presently damaged by flood flows in the Colusa Basin. Engineering and Economic Studies Studies to analyze properly the engineering feasibility and economic justification of the above-stated alternatives, particularly the levee and drainage projects, may be grouped into four general categories; hydrology, hydraiilics^ economics, and design. Hydrology studies included estimates of the magnitude of floods and probable frequency of flooding with existing drainage channel facilities under present and future conditions of land use. The development of these relationships was based on a combination of regional hydrologic studies and streamflow records in the area. Hydraulic studies consisted of analyses of the effects that the varioixs proposed projects would have on flows of various magnitudes. The results of these studies were used primarily in the design of projects for the control of the various sized floods investigated. The hydraulic capacity of existing chsinnels was determined from rating curves for stream gaging stations or by field survey methods. -7- Economic studies were made to determine the benefits \Aich would accrue to the various projects considered. Since the benefits would consist primarily of damages prevented, extensive field work was done in estimating the types and amounts of historical damages. In determining these benefits, a land use study was made for existing and projected future land use within the historically flooded areas. Design studies were limited to preliminary designs and estimates of cost. While these designs are not of the detail required for actual construction, they are of sufficient accuracy to provide a measure of project feasibility by comparing estimated costs with benefits. After the economic Justification of the Yolo Bypass Project was determined, a detailed review of design and cost estimating criteria was made. The costs reported for the Yolo Bypass Project reasonably represent I961 construction costs, and are adequate for the purposes of this investigation. Related Investigations and Reports A review of related investigations and reports, both published and unpublished, has provided much of the background and data needed to conduct this investigation. A great deal of infonnation relative to the history and reclamation of the Colusa Basin was obtained from files of the Reclamation Board of the State of California. Basic data concerning stream flow and floods were obtained from publications of the U. S. Geological Survey, the U. S. Corps of Engineers, the U. S. Bureau of Reclamation, and the State of California Department of Water Resources. The U. S. Corps of Engineers has made numerous studies in con- nection with the Sacramento River Flood Control Project. Although no specific report pertaining to the Colusa Basin has been published, several reports have included information useful in evaluating the flood and drainage problems of the Colusa Basin. -8- The U. S. Bureau of Reclamation, in connection with its responsibili- ties for the Central Valley Project, has also published information useful in evaluating the problems of the Colusa Basin. Investigations and reports in connection with the Sacramento Canals Lhit, Sacramento Valley Project, were particularly helpful in estimating future flows in the Colusa Basin. Organization of Report The report on the Colusa Basin Investigation is presented in the ensuing chapters. Chapter II discusses the "Geography and Economy" of the Colusa Basin and is intended to acquaint the reader with the physical features of the basin, the flood control and irrigation works developed during its history, and the economic development that is affected by its flood and drain- age problems. Chapter III, "Existing and Potential Flood and Drainage Problems, " presents information relating to present and future flood and drainage prob- lems with the hydrologic analysis needed to design corrective works. Flood damages that presently occur, ajid that would occior in the future without project development, are also presented. "Possible Solutions" are discussed and analyzed in Chapter IV. Chapter V is a summary of conclusions and recommendations. In addition to the illustrations and figures included in the bulletin, six plates are bound following the text. Of particular interest is Plate 1, "Existing and Possible Flood Control and Drainage Features," showing the area of investigation, historically flooded areas, and the locations of possible improvements. -9- CHAPTER II. GEOGRAPHY AND ECONOMY The Colusa Basin is a shallow trough lower in elevation than the Sacramento River that borders it on the east. In its natural state, the basin was subjected to overflow from the Sacramento River whenever the capacity of the river channel was exceeded during winter floods and spring snowmelt floods. Annual flooding was common. Precipitation within the area, as well as runoff from the western foothills, added to the flooding. The present agricultural development of the Colusa Basin has been made possible by the flood control and reclamation features constructed by the individual and cooperative efforts of local, state, ajid federal agencies. Many of the flood control works protecting the basin from floods have been construc- ted as part of the extensive Sacramento River Flood Control Project. Agricult\iral activities are the most significant factor in the area's economy. Considerable recreational activity also takes place in the form of hunting for ducks, geese, and pheasants. Waterfowl are attracted to the Colusa Basin in their seasonal migrations by the presence of extensive flooded areas. Area of Investigation The Colusa Basin is one of several similar basins that are located in the Sacramento Valley. The several basins adjoin the Sacramento River ajid are separated by the major tributaries of the Sacramento River System. The Sacra- mento River collects runoff from the entire Sacramento Valley and conveys this water to Suisun Bay. The basins generally can be described as depressed areas or shallow troughs located on each side of the Sacramento River. The Sacramento River flows on an elevated ridge that has been built from the silt and sand carried by the river during times of flood. The basins were formed by the gradual -11- building up of the bemks of the river from sediments deposited as the water overflowed its natural channel. The heavier and larger sediments carried by these flood flows were deposited on the banks and near the main channel while the finer, smaller particles were carried considerably further from the main channel. The slope of the groxind away from the main channel is relatively steep and gradually flattens towards the center portions of the basins, which are generally 6 to 20 feet lower than the river banks. IXirlng seasons of heavy rainfall, and before the present system of levees in the Sacramento Valley was constructed, the flood basins or troughs were filled by runoff from the adjacent plains and hills, and by water from the main river flowing over the banks. The basins usually discharged through sloughs, either back into the main channel, or into the next lower flood basin. In times of great prolonged floods, these basins performed a dual fiinction, acting both as large shallow flood water channels and as temporary storage or equalizing reservoirs that reduced the peak of the floods. The basins would remain full of water xintil the river receded to a stage that would allow the basins to drain. Colusa Basin The Colusa Basin is one of two major basins lying west of the Sacra- mento River. The Yolo Basin, located southerly of the Colusa Basin, is sepa- rated from the Colusa Basin by the Knights Landing Ridge. This ridge was formed by sediments from Cache Creek deposited in a manner similar to those deposited by the Sacramento River. The Colusa Basin extends over portions of the counties of Glenn, Colusa, and Yolo. The exact limits of the Colusa Basin are not precisely defined, but generally include those lower lands that may be covered by flood water. The Colusa Basin has an overall length of approximately 70 miles and a maximiun width of about eight miles. It is divided into an upper -12- and lower basin by a small ridge created by the sedimentary deposits from Upper Sycamore Slovigh. The upper basin is a comparatively narrow tract of land, generally not more than four miles in width. Colusa Basin Drainage Area The drainage area of the Colusa Basin extends from the Sacramento River on the east to the crest of the foothills on the west. Stony Creek and Cache Creek are the approximate northerly and southerly boundaries, respec- tively. The Colusa Basin drainage area, identified on Plate 1, includes about 1700 square miles. Plate 2, "Irrigated and Irrigable Lands, 195'+-56" shows the location of the agricultural lands within this area. Water agencies serv- ing the area are shown on Plate 3> "Principal Irrigation Water Service Agencies and Proposed Water Se]*vice Areas." The physical works of the water agencies and the various reclamation and levee districts located within the area are important factors in the agricultural economy of the Colusa Basin. The various reclamation and levee districts are shown on Plate k, "Reclamation and Levee Districts." ■13- Topography and Geology Figure 1, a generalized east-west geologic section across the Colusa Basin near Grimes, depicts the topography of the Colusa Basin drainage area. The geologic classification of the subsurface materials also is indicated in this figure. The foothills and uplands which are shown in about the western one-third of the figure are part of the Coast Range. The remainder of the figure shows the relatively flat floor of the Sacramento Valley. DISTANCE IN MILES Figure I GENERALIZED GEOLOGIC SECTION ACROSS COLUSA BASIN NEAR GRIMES The hills and mountains of the Coast Range are composed mainly of sedimentary sandstones, shales, and conglomerates. These hills, in the western portion of the Colusa Basin drainage area, resemble a giant deck of cards stacked nearly on edge. The more resistant strata stand out as ridges, while the intervening, less resistant have been worn down by erosion. .Ik- This is illustrated by the photograph on pagelo. The sedimentary strata dip beneath the valley, lie thousands of feet beneath the central part of the valley, and emerge on the other side in the foothills of the Sierra Nevada. The valley floor was formed primarily by the deposition of mate- rial carried by flood waters of streams. Geologically, the principal formations of the valley are the alluvial fan deposits, the flood basin deposits, and the river deposits. The alluvial fan deposits were laid down by streams draining the Coast Ranges and vary in composition from clay to gravel. Deposits of the Sacramento River include channel deposits, natural levees, flood plains, and flood basins. All but the flood basin deposits were laid down by active waters and are primarily coarse grained. The flood basin deposits, which make up a major portion of Colusa Basin proper, are mostly composed of fine-grained material deposited by slowly moving or standing water. Soils Soils in the Colusa Basin vary in their chemical and physical characteristics in accordance with differences in their parent material, drainage, sind age or degree of development since their deposition. The soil characteristics exercise a strong influence on the relationship be- tween precipitation and runoff. The principal influence of the coarse- textured soil in the western foothill area is that runoff results only after very heavy, sustained storms. The soils of the valley floor are finer-textured and much less pervious; consequently, a higher percentage of the precipitation tends to run off. However, the valley lands are relatively flat and runoff is slow. Most of the fine-textured valley floor soils having slow to very slow permeability rates were dei*ived from slow moving flood water. •15- The more resisfanf sfrafa stand ouf as ridges, while the intervening, less resistant have been removed by erosion. A large part of these clayey soils are affected to varying degrees by concentrations of soluble salts or exchangeable sodium. Those affected by soluble salts are called saline soils, and those with an excess of exchangeable sodium are known as alkali soils. Both of these conditions have occurred primarily as the result of poor drainage, a slow permea- bility rate, a high ground water level, and a high rate of evaporation during the summer. Alkaline soils resulting primarily from sodiiun sul- phate (glaubers salt) occur in most of the basin. The crop adaptability of these fine-textured, salt-affected soils is greatly restricted at the present time. The improvement of drain- age conditions would assist markedly in bringing about their reclamation. Dispersed throi:ighout the area are relatively small bodies of coarse - textured soils which were derived from depositions of fast-moving flood waters and lie adjacent to stream channels. These soils have good perme- ability, are free of soluble salts or exchangeable sodium, and are suitable for a wide ramge of climatically adapted crops. Climate The climate of the Colusa Basin is characterized by dry sximmers with high daytime temperatures and warm nights, and wet winters with moderate temperatures. More than 80 percent of the precipitation occurs during the five-month period from November through March. The growing season between killing frosts is long; the average for Colusa, located centrally in the area, is about 288 days. The average for Willows is 22^4- days. Temperatures at Colusa have ranged from 1^4- F. to ll4 F. for the ^7 years of record; the monthly average ranges from '+5°F. in January to 78 F. in July. Temperatures at Willows have ranged from 15°F. to ll6°F., 8Lnd the monthly average ranges from h^ F. in January to 80°F. in July. -17- Population The Colusa Basin has had a gradual increase in population as indi- cated by census figures from I920 to I96O. Table 1 shows this trend by counties as well as projected increases over the next 60 years. Population figures for the northern part of Yolo Coxmty, Knights Landing Division, located in the Colusa Basin, indicate an increase more similar to that expe- rienced in Colusa County than that in the remainder of Yolo County. Future population increases in the Colusa Basin drainage area are expected to follow the trend predicted for Colusa and Glenn Counties. TABLE 1 POPULATION DATA AND PROJECTIONS- (in thousands) 1/ Years : Colusa County : Glenn : County : Yolo : : County : Yolo County Knights Landing DLvisionl' 1920 9.3 11.9 17.1 1930 10.3 10.9 23.6 2.8 l9i^o 9.8 12.2 27.2 3.1 1950 11.7 15. i^ i+0.6 3.2 i960 12.1 17.2 65.7 3.0 1970 13.8 22.6 91.8 1980 17. k 30.0 136.0 — 1990 27.0 U2.8 209.0 2000 ^+3.7 60.3 319.0 2010 6k.5 80.5 i+53.0 2020 89.0 lOi^.O 6ih.o — 1/ Projections of population are Department of Water Resources estimates as ~ of September I96O. 2/ The Knights Landing Division is defined by the U. S. Bureau of the Census in the I96O census. For other years, the svm of the populations of the Blacks, Cacheville, Dunnigan, and Grafton Townships are used. -18- Reclamation The development of Colusa Basin into a productive agricultural area has been dependent upon the progressive reclamation of the area to prevent flooding, improve drainage, and provide irrigation. Individ\ials, local districts, state and federal agencies, through the yearr. have con- structed various works necessary to the farming of the fertile acres lo- cated within the basin. Local reclamation districts were the first agencies to develop the area for agricultural purposes. Investigations and proposals by the state and federal government, in the early 1900's, concerning flood protection in the Sacramento Valley greatly influenced the subsequent devel- opments within the Colusa Basin. In 1850, through the passage by Congress of the Arkansas Act, the State of California obtained from the federal government approximately one and three-quarter million acres of swamp and overflow lands. In accepting these lands, the State was obligated to reclaim them as far as practicable. Laws in lQ35, I856, and I859 provided for sale of these lands to the public at a price of $1.00 an acre in tracts not to exceed 6hO acres, with the con- dition that the purchaser should reclaim portions of the land. A more defi- nite system of reclamation of swsjnp and overflow lands was established in 1861 when the State assumed direct responsibility for reclsimation. In doing so, it established a board of Swamp Land Commissioners to plan, authorize, and supervise reclamation works; and it impowered districts to levy assess- ments to raise funds for reclamation projects. These duties and responsi- bilities undeirwent numerous changes until the reclamation districts as presently constituted were established. Reclamation districts have been effective agencies to accomplish initial reclsimation, not only in the Colusa Basin but also in extensive areas of the Delta, and Sacramento and San Joaquin Valleys. Their -19- activities hastened agricultural development in California. However, recla- mation was accomplished bit by bit, without coordinated planning; and im- provements in one area often would worsen flood hazards in another area. The Sacramento River Flood Control Project, a Joint venture of local, state, and federal agencies, received federal sanction in 1917' Because initial reclamations by local districts have been modified subsequent- ly to conform to the general plans developed for the Sacramento River Flood Control Project, a brief discussion of that project will be presented first. The description of works constructed by local districts, which in some instances were initiated prior to the conception of the Sacramento River Flood Control Project, will follow the discussion of that project. Sacramento River Flood Control Project The Legislature of the State of California, on December 2k, I9II, approved the California Debris Commission plan for controlling floods of the Sacramento River and created the State Reclamation Board to supervise the carrying out of this project. The Sacramento and San Joaquin Drainage District, which included practically all of the overflow land in the valleys of Sacramento and Saji Joaquin and which comprised some 1,750,000 acres, was organized in 1913« The Reclamation Board was charged with its supervision. The Sacramento River Flood Control Project, as adopted by the State of California in I9II, was authorized also as a federal flood control project in 1917 • Although subsequent modifications to the basic plan have been authorized by both the state and federal governments, the original con- cepts proposed by the California Debris Commission have been substantially followed. The bypass concept was adopted after the floods of I907 and I909 demonstrated the insufficiency of the proposals to confine flood flows to the main river channels. The bypass concept is based on the diversion of -20- flood flows from the main channel to an aiixiliary channel or bypass. The concentration of flooding in the winter months has made it possible to utilize the bypass areas for agricultural pursuits during the remainder of the year in all but those years when flood flows persist beyond the planting period for crops. The project, now substantially completed, consists of a compre- hensive system of levees, overflow weirs, drainage pumping plants, and flood bypass channels. The bulk of the flood flows passing through the Sacramento Valley is conveyed by weirs from the Sacramento River to the Sutter Bypass and Yolo Bypass. Flood waters then continue downstream and return to the Sacramento River in the vicinity of Rio Vista. The original proposal to construct a bypass in Butte Basin has never been implemented. Floods continue to discharge by over-bank flow into Butte Basin which acts as a natural detention basin reducing inflow to the upper end of the Sutter Bypass. Work on the Sacramento River Flood Control Project within the Colusa Basin has been done by the state and federal governments as recently as 1958. This work resulted in the improvement of the back levee of Recla- mation District No. IO8 from PCnights Landing to high ground in the vicinity of Colusa. In early years, proposals were made for a bypass through the Colusa Basin, generally along the alignment of the Colusa Basin Drainage Canal. This bypass would have carried Sacramento River flows safely through the Colusa Basin area, as well as collecting and providing drainage for local runoff occurring within the Basin. The construction of the Sutter By- pass, on the east side of the river, as part of the Sacramento River Flood Control Project to cariy Sacramento River flood flows eliminated the need -21- for a similar bypass in the Colusa Basin. Consequently, desirable drainage features which would have been included with the proposed Colusa Basin by- pass were not constructed. Works Constructed by Local Districts The levee system and reclamation works within the Colusa Basin in many instances have been constructed by the reclamation districts, the locations of which are shown on Plate h. Construction activity by these districts staji^ed in 1868. In the discussion which follows only the more significant activities as related to the key flood control and drainage features will be discussed. The activities of the several districts involved are discussed in regard to the major reclamation features including the river levee, the back levee, the Knights Landing Ridge Cut, and the Colusa Basin Drainage Canal. River Levee . Flooding from the Sacrajnento River was the initial concern of Reclamation District No. IO8, and its early activities were devoted to providing a levee system which would prevent this flooding. The district eventually constructed and maintained a levee on the right, or west, bank of the Sacramento River between Knights Landing and the town of Sycamore in Colusa County. The total length of this levee system was about 39 miles. The district also was interested actively in the extension of this levee upstream about kO miles more. It contributed the greater portion of the funds required to construct the upper portion. Throughout early years, construction work was continued, maintenance was performed, and weaker sec- tions of the levee were strengthened. In 1915 the Sacramento River West Side Levee District assumed the maintenance of the river levee upstream from Eldorado Bend. Reclamation District No. 787, formed in I908, assxamed the maintenance of the lower nine miles of river levees extending southerly from Eldorado Bend to Knights Landing. -22- The construction of this river levee blocked the natural drainage outlets from the Colusa Basin. Each spring the accumulated drainage would be released back to the river by the cutting of the levee at Knights Landing. This necessitated the reconstruction of the levee before the next winter's river floods. As early as I883, a structure with automatic gates was pro- vided to allow for drainage from the basin. This solution, however, was not effective because it was generally late in the planting and growing season before the accumulated drainage waters could be released. To permit releases while high stages prevailed in the Sacreunento River, a drainage pumping plant at lower Sycamore Slough was constructed in I885 . Back Levee . The back levee of Reclamation District No. IO8 has been improved and strengthened progressively to conform fully with require- ments of the Sacramento River Flood Control Project. Its present alignment easterly of the Colusa Basin Drainage Canal is shown on Plate 1. The back levee extending from Knights Landing to high ground near Colusa protects lands to the east from flood runoff of the western foothills. In early years, considerable difficulty was encountered in maintaining portions of this levee. Limited funds were available and, consequently, levee sections were not nearly as massive as they are at present. In flood periods, an extensive lake would form west of the back levee; then wind-caused waves would wash away the levee sections. In early years, breaks were frequent. In some years ponding became so extensive that flood waters would overtop the levee and flood the reclaimed area, and would also overflow the Knights Landing Ridge to flood lands in the Yolo Basin. Drainage through the Knights Landing outfall gates was impossible because of high water in the Sacramento River. Not until 1958 was the back levee brought to full stand- ards of the Sacramento River Flood Control Project. -23- Knights Landing Ridge Cut . In 1913 > the Knights Landing Ridge Drainage District was formed to develop a plan to provide an outlet for water ponded between the back levee and high ground on the west and south. Drainage of this water would be further restricted from flowing through the Knights Landing outfall gates by high stages in the Sacramento River. The district proposed a cut through the high ground on the south to pro- vide an outlet for the ponded water. The Knights Landing Ridge Cut subsequently was dredged through the Knights Landing Ridge for a distance of about seven miles. This cut terminated in low lying land in the Yolo Basin at the western edge of what is now known as the Yolo Bypass. The cut is about ^4-00 feet wide on the bottom and has a raaxiraum depth of nearly 20 feet. It has a discharge capacity of about 20,000 second-feet when the water surface elevations (used datum) are 39 feet at Knights Landing and 35 feet at the Yolo Bypass. The ridge cut was completed and in operation during the flood of September 1915. The Knights Landing Ridge Cut provides a gravity outlet for floods occurring in the Colusa Basin. The outlet does not prevent the flooding of extensive areas along the Colusa Basin Drainage Canal during flood periods, but it greatly reduces the length of inundation. Colusa Basin Drainage Canal. As development of the irrigated lands in the Colusa Basin continued, return flows from irrigation during certain periods of the year created flooding problems downstream from the areas irrigated. Because of the inadequacy of the drainage facilities within the Colusa Basin, Reclamation District No. 20^7 was formed on Dscember 16, 1919* This district developed a plan and constructed physical works designed to handle the anticipated irrigation return flow. .2k. T3 .S —- 5g- -0 e o 0) 0) ID E D) 11 1^ — o d) "^ -C c .£ 0) "D c o o c ^ D O O 0) The principal feature of Reclamation District No. 20^+7 ' s plan was the Colusa Basin Drainage Canal. South of its junction with Willow Creek the canal proceeds southerly to the vicinity of Colusa and then follows the alignment of the back levee constructed by Reclamation District No. 108 and others. The borrow pits used for obtaining material in building the back levee were utilized for this channel. Considerable excavation was required in some reaches to provide a continuous drainage canal of desired capacity. This canal terminates at the Knights Landing outfall gates on the Sacramento River in Yolo County. The design capacity of this canal is 1,^50 second-feet with the elevation of the water surface at a minimum of one foot below the adjoining land so as to provide drainage to the lands along its entire align- ment. The canal was designed to convey irrigation return flows from 101,000 acres of rice located in Reclamation District 20^7 and in production in 1920. In addition to this main canal, a branch chsuinel was constructed. This channel followed the common boundary between Reclamation Districts 108 and 787, and connected to the Sacramento River at Eldorado Bend. A pumping plant at this point was originally constructed to pump flood waters into the Sacramento River during periods when the Knights Landing outfall gates were closed because of high stages in the Sacramento River. The pumping plant is not used for flood relief however, but pumps water from the Sacramento River to irrigate several thousaind acres adjoining the branch canal and within Reclamation Districts IO8 and 787. The Colusa Basin Drainage Canal also serves as a water supply facil- ity for lands adjoining the canal. To be effective as a source of supply, the water surface must be maintained at a level adequate for pumped diversions. A small control structure with limited outlet capacity at the lower end of the Knights Landing Ridge Cut accomplishes this purpose. The elevation of this control at the mouth of the Knights Landing Ridge Cut is sufficiently low that the major floods, usually occurring during the winter flood season, can be -26- 0) > Si o 2 c o 00 o o c % o o c o . 0) 0) H o c CO o ? ° A pumping planf on a branch of fhe Colusa Basin Drainage Canal was originally con- sfrucfed fo pump flood waters info the Sacramento River. However, it is not used for flood relief, but supplies irrigation water to lands in the Colusa Basin. discharged into the Yolo Bypass. In the fall, when large irrigation return flows are conveyed by the Colusa Basin Drainage Canal, the water level in the Saci"amento River is sufficiently low so that the water can be readily discharged through the Knights Landing outfall gates. In the spring, how- ever, irrigation return flows cannot be adequately discharged. At this time, the water level in the Sacramento River usually is too high to permit gravity drainage. Also, discharge of water into the Yolo Bypass creates further problems at this time. The problem of inadequate drainage will be discussed more fvlly in the next chapter. Agricultural Development Settlement of the Colusa Basin commenced shortly after surveys were made by General John Bidwell in the l8ij-0*s. Early settlers took up laJid grants from the Mexican government. Navigation of the Sacramento River and the proximity of available land to the river were responsible for the first settlements taking place along the river. The production of grain became of major importance in the years that followed. Grain raising received its impetus from the demand created by the large number of freight teams hauling supplies to the mines in the Sierra Nevada. Large acreages were planted to dry-farmed wheat and barley; but near the turn of the cen- tury, production of those grains declined and the emphasis turned to irri- gated crops. Irrigation Works In conj\inction with the reclamation of the Colusa Basin, irriga- tion works were developed. Irrigation facilities have been provided by irrigation and other type districts, as well as by individuals. The waters of the Sacramento River initially were developed for irrigation use. After -29- construction of the Colusa Basin Drainage Canal irrigation return flows were used by irrigators along this channel. Irrigation District Dsvelopments . One of the earliest irrigation schemes was promoted by Will S, Greene of Colusa in l86U, and was to consist of a large irrigation and navigation canal to serve Colusa and Yolo Counties. Not vmtil after passage of the Wright Act in I887, however, was progress made toward bringing water from the Sacramento River to the lands. The Central Irrigation District, organized in November I887, was the fourth irrigation district to form in the State. This district embraced an area of 156,550 acres in what was then Colusa Coiinty (now Colusa and Glenn Counties). A por- tion of the Central Canal was constructed, but financial difficulties post- poned progress for several years. In 19^3^ private interests provided capital to complete the cajial and constructed a pumping plant at the river intake. The first water was delivered in I906. In the years that followed, the dis- trict was plagued with n\:imerous problems, involved in litigation, and troubled with financial problems. As a result, six districts were formed between I916 and 1920 to take over the system and the area originally embraced in the Central Irrigation M-strict. The divided area comprised the Glenn-Colusa District, about one -third of the Jacinto Irrigation District, about half of Provident Irrigation District, and most of Compton-Delevan, Maxwell, and Williams Irrigation Districts. The largest of these is the Glenn-Colusa Irrigation District, which now serves about 112,000 acres. Table 2 lists the irrigation districts in the Colusa Basin that pro- vided water in 1959^ and indicates the acreage irrigated and the amounts of water delivered. The table includes similar information for other water serv- ice agencies, as well as for the larger private irrigation developments. The location of the larger public districts is shown on Plate 3» -30- TABLE 2 PRINCIPAL WATER USERS IN THE COLUSA BASIN IN 1959 Name : Water delivered, : Presently irrigated in acre -feet area, in acres Mutual Water Companies Willow Creek Mutual Water Company (included with Glenn -Colusa I.D.) Colusa Irrigation Company 1,15^ 2ti9 Roberts Ditch Compajiy 3,678 1,032 Irrigation Districts Glenn -Colusa 824,455 78,700 Jacinto 85,210 9,738 Maxwell 16,000* 4,000 Princeton -Cordora -Glenn 78,673 6,162 Provident 104,856 8,532 Reclamation Districts Number 108 192,736 26,215 Federal Fish and Wildlife Service 6,572 880 Private River Farms 28,541 4,354 0. P. Davis 25,323 3,615 J. H. Zumwalt 17,344 4,848 Charles W. Welch 13,836 2,691 Layton Knaggs 9,880 959 Beckley, et al. 7,662 579 C. W. Tuttle 5,606 848 Seaver and Byington 5,464 784 Fred Schultz 3,1^^ 1,120 Hershey Estate 5,062 720 ♦Estimated -31- Many of the pumps are locafed on feeder canals some distance from ihe main drainage canal. In fhe western and especially northern portions of the basin, ground wafer pumping provides a water supply. Private Irrigation Development . Outside of the organized dis- tricts, private landowners also have constructed irrigation facilities. These developments began at an early date with pumping from the Sacramento River. Somewhat later, following the establishment of a more-or-less firm return flow through the Colusa Basin Drainage Canal, land was brought under irrigation by pumping from the drainage canal and feeder canals. This latter development has been possible because of the very low land gradient adjacent to the drainage canal. A typical installation located on a feeder canal is shown in the top photograph of the facing page. The water is con- veyed westward by canals in cut and fill with low pump lifts. Irrigation is then accomplished by gravity. In the western and especially the northern portions of the basin, ground water pumping provides part of the water supply . The lands along the Colusa Basin Drainage Canal are served either by pump diversions from the canal or by wells or by both in some cases. Mainy divertors have filed applications for water rights. Filing began shortly after the enactment of the Water Commission Act (Statutes 1913> Chap- ter 586). Due consideration of these water rights and conditions of use is mandatory in planning for flood control or drainage improvements. In this regard, field investigation and interviews with irrigators showed that in any proposed summer drainage improvement, water levels must be maintained in the Colusa Basin Drainage Canal to permit existing diversions to continue unimpaired. Proposed Irrigation Development Large areas of land in the Colusa Basin remain undeveloped, partic- ularly the higher lands to the west. The U. S. Bureau of Reclcimation, as -33- part of the Central Valley Project, has plans to provide water to irrigable lands within the Colusa Basin. The service areas in which irrigation water will become available are indicated on Plate 3« Water Quality Water quality is not presently a problem, at least insofar as the quality of an irrigation supply from the Sacramento River or the Colusa Basin Drainage Canal is concerned. Studies by the Department of Water Re- sources indicate that the quality of water in the Sacramento River will continue to be excellent in future years. Water quality information, par- ticularly that applicable to the Colusa Basin Drainage Canal, was reviewed for this investigation. Since 1952, a series of periodic water quality samples have been taken from the Colusa Basin Drainage Canal at Highway 20 and Knights Landing. Mineral analyses of these samples indicate a fairly consistent water quality dviring the irrigation season. Of the 63 samples taken from the lower part of the Colusa Basin Drainage Canal over a period of nine years, only two samples failed to meet the standards of Class I water. Both of these were taken during a very dry spell in April and May 195'+. Fish and Game Recreation, measured in terms of money spent, is one of the most important activities in the Colusa Basin and is exceeded only by agriculture as a factor in the local economy. Hunting, particularly for pheasant and waterfowl, constitutes the principal form of recreation in this area. The many sloughs, channels, and drains in the Colusa Basin also sustain warm- water game fish. Catfish and largemouth black bass are the principal game fish. Lesser numbers of bluegill and green sunfish are also taken. Most of these game fish appear in the Colusa Basin Drainage Canal and in channels or .3h- ponds on permanently flooded gun club lands along Willov Creek. The numer- ous irrigation ditches and drainage ways in the area are also heavily fished. Fishing for striped bass and salmon occurs primarily in the Sacramento River, The Pacific Flyvay, one of the four major waterfowl migration fly- ways within the North American Continent, covers California, Oregon, Washing- ton, Idaho, Montana, Nevada, Utah, and Arizona. Ducks and geese using the Pacific Flyway nest and breed, for the most part, in Alberta and Saskatchewan, sind move southward to winter in California, Arizona, and Mexico. The breeding areas have been affected only slightly by man's activities, although winter- ing areas to the south, particularly in the Central Valley in California, are continually reduced as a result of increases in population and accompanying increases in land use. Consequently, the two areas are seriously out of bal- ance. Waterfowl populations are limited by insufficient wintering areas, even though their northern breeding areas are sufficient to support a larger water- fowl population. Throughout recorded history, California has been the principal wintering ground for migratory waterfowl of the Pacific Flyway. An estimated 60 percent of Pacific Flyway waterfowl winter in California. Extensive marsh areas in the great valleys of the State were used, prior to reclamation, by hordes of ducks and geese. Today these same valleys have a much reduced marsh and water acreage, and are crowded with waterfowl during the winter season. Figure 2 shows the several major routes within the flyway as well as the complex of branching routes, concentration points, and interchanges between subflyways. At least seven migration routes converge at the Tule Lake- Lower Klamath concentration area, one of the largest in the nation. From there the birds move in great flocks down into the Central Valley of California. -35- * X \' c • • v^ o c o V O) o 0) _2 o i T3 c o o E "S § T3 5 ^ o o a, ». E 5 o > s * "X3 Figure 2 PACIFIC MIGRATORY WATERFOWL FLYWAY, SHOWING PRINCIPAL FALL MIGRATION ROUTES The Colusa Basin is vithin the most important wildlife area in the Sacramento Valley. The basin contains two federally-owned national wildlife refuges, the Sacramento National Wildlife Refuge near Willows, and the Colusa National Wildlife Refuge near Colusa. These two refuges, together with the state-owned Grey Lodge Waterfowl Management Area in Butte County, the Sutter National Wildlife Refuge in Sutter Covmty, and adjoining areas provide the bulk of the waterfowl wintering grounds in the Sacramento Valley. This area contains 2'+,000 acres of federal and state -owned water- fowl refuge and waterfowl management areas as well as an estimated 33^000 acres of privately owned gun club lands in Butte and Colusa Basins. U. S. Fish and Wildlife Service records from 1953 through 1957 show that 78 per- cent of the ^+65,000 migratory waterfowl in the Sacramento Valley in September occupy these four refuges. The state and federally-owned areas serve primarily to supply needed habitat for feeding and resting as well as refuge areas for water- fowl and other species of wildlife. These areas also function to alleviate crop depredation. During the period from August to October before rice is harvested, rice fields are subject to serious monetary losses due to depre- dation by ducks. Much of this economic loss has been alleviated in recent years by the growing of crops on the state and federal waterfowl areas, and the attraction of birds to these areas during the critical rice harvest period. The Colusa Basin provides one of the best pheasant producing areas in the State. Each year, Colusa County sustains the heaviest kill of pheas- ants of any county in the State, Other gajne birds in the basin include the widely distributed mourning dove and the far less numerous California quail. -38- Naturally, the vetland habitat associated with waterfowl supports a great variety of wildlife other than game birds. Widely distributed spe- cies of these birds include large numbers of shore birds, egrets, herons, swans, grebes, and pelicans. In addition the riparian habitat existing along ditches, drainage, and waste ways supports large numbers of songbirds. These forms of wildlife, as well as the game species, are part of our wild- life heritage. Skionk, opossum, racoon, fox, otter, mink, and rauskrat occur in the basin. Muskrat, damaging as they are to irrigation works and agricul- ture, provide commerce in the winter months to a few people who trap for furs. The Colusa Basin is the most heavily hunted area of comparable size in the State. Considerable hunting takes place on lands subject to flooding. In the flood of February 1958, 93^000 acres were flooded. In this area, 21,000 acres are devoted to waterfowl management, either in the Colusa National Wildlife Refuge or in commercial or private gun clubs. Most of the rest of these 93*000 acres are devoted to pheasant hunting. In an average year 72,500 hunter-days are expended in waterfowl hunting and 27,000 in pheasant hunting on the area subject to flooding. In the Colusa Basin as a whole, 166,000 acres are devoted to pheasant hunting in cooperative or commvmity hionting areas ajid at licensed pheasant clubs. On these lands, 52,600 hunter-days are expended on pheas- ant hunting annually, and fees of over $60,000 are collected. -39- CHAPTER III. EXISTING AND POTENTIAL FLOOD AND DRAINAGE PROBLEMS Flood conditions, including those arising from poor drainage, impede agriculture and economic development in portions of the Colusa Basin. Problems of flooding exist along V7illow Creek, along the Colusa Basin Drainage Canal and its tributary drainage channels, and in portions of the Yolo Bypass below the Knights Landing Ridge Cut. These problems are caused by improper and insufficient individual farm drainage, inade- quate facilities to remove drainage from low lying areas into the Colusa Basin Drainage Canal and other major drainage canals, insufficient channel capacities of flood and drainage canals tributary to the Colusa Basin Drainage Canal, and inadequate discharge capacity of the Colusa Basin Drainage Canal into either the Sacramento River or the Yolo Bypass. The scope of this investigation was restricted to meet the objectives of Senate Concurrent Resolution No. 79 with available funds and within available tim». Problems investigated in detail vrere those of flooding and drainage along a portion of Willow Creek and along the Colusa Basin Drainage Canal and the inadequate discharge capacity of that canal. Flood and drainage problems along channels tributary to the Colusa Basin Drainage Canal were considered only in connection with their relationship to problems of the main canal. The area of study was limited to that downstream from the Willow Creek area studied by the U. S. Corps of Engineers, and areas downstream from the Glenn-Colusa Irrigation District Canal crossing of Willow Creek just east of the town of Willows. The study area extends downstream along the Colusa Basin Drainage Canal, the Knights Landing Ridge Cut, and the Tule Canal in the Yolo Bypass as fax south as the Sacramento Deep Water Ship Channel. -l;l- Existing Flood Problems During the winter flood period, roughly October through March, floods are caused by precipitation within the basin and runoff from the foothill region to the vest. The magnitude of the discharge in these winter storms is very large when compeired with the channel capacity of the Colusa Basin Drainage Canal. The channel capacity in the upper reaches, for example, is exceeded when the discharge at Highway 20 near Colusa is greater than 2,100 second-feet. The maximum mean daily discharge of record occurred on February 21, 1958> and vas 23,900 second-feet at that point. Because the channel is inadequate to handle the discharge, the excess flows flood an extensive area alor^g the channel. In 1958? the flooded area extended continuously from Knights Landing to Orland, a dis- tance of 70 miles. The flooded areas are frequently large at this time of year, but the damages are relatively light since the lands inundated are principally agricultural and idle during the winter. Highways, roads, and public utilities, as well as the limited urban or domestic development within the flood plain, are also subject to damage. Existing D'-ainage Problems In the spring months, April through June, flooding is caused principally by irrigation return flows rather thnxi by precipitation. During the spring, precipitation is generally insignificant. The channel capacity of the Colusa Basin Drainage Canal is usually adequate to handle the irrigation return flows, except in the reach between College City and Knights Landing where flooding of a small area occiirs regularly. The resulting damages are large since this flooding occurs in the normal growing season. This spring flooding results from local agricultural -1;2- practices which cause irrigation return flows that cannot be dissipated by- works constructed to relieve winter flood conditions. Virtually all of the rice in the Sacramento Valley is planted between April 15 and May 15- In order to control weeds, the rice fields are flooded to a depth of 10 to 12 inches for a period of three to four weeks. In this time, both the rice and weeds germinate, and both would be drowned out if this depth of water were retained. The rice has a somewhat longer life under the deep water, however, and, after the weeds have died but before the rice is harmed, 4 to 6 inches of water is dumped from the fields. The acreage of rice in the Colusa Basin is very large; in recent years, it has averaged around 100,000 acres, reaching a peak of 131,000 acres in 195^' Since the planting and flooding schedule for all this rice is about the same throughout the basin, the dumping practice creates a considerable flow that generally reaches a peak in May. The resulting flow may be augmented by water that must be released from rice fields during sustained north winds prevalent at this time of year. Most rice fields are large and have a considerable fetch, particularly in a north-south direction. Conse- quently, the water piles up at the south end of the field. In order to protect his checks, the grower must allow part of the ponded water to escape. Several conditions contribute to the inability of existing works to handle spring flooding. High water in the Sacramento River prevents the drainage water from escaping through the Knights Landing outfall gates into the river. The outlet of the Knights Landing Ridge Cut is inadequate to release the required flow. Backwater resulting from these conditions causes flooding of lands along the west side of the Colusa Basin Drainage Canal. Whatever water does escape into the Yolo Bypass causes additional damage by flooding farm land which has been planted at this time of year. .1+3- ^*- '^ «* ■^t? o o o o o c 3 O 0) '5> o > o ^~ la c o o CQ s _3 o U 01 -c Q) o *C 0) **- >v .^ c a between College City and Highway 20; Reach k, between Highway 20 and the Colusa-Glenn Coiinty line; Reach 5^ between the Colusa-Glenn County line and Willows. Reach 6, an area northwest of Willows, was considered briefly in the study of the foothill reservoir system. Frequency and Degree of Flooding Studies of flood frequency were based upon historical records of precipitation and flood runoff in the Colusa Basin. A statistical de- termination was made of the possibility of occurrence of various sizes of floods. The February 1958 flood in the Colusa Basin in Reaches 3, ^, and 5 was of a size that probably would be equalled or exceeded two percent of the time, or an average of once-in-50-years. The expression of probability of annual occurrence of various sizes of floods as a percentage is preferred because it does not imply that this size of flood occurs only at widely spaced intervals. -53- Figiu-e 3 shows the probability of aimual occurrence of various sizes of floods in Reaches 3, ^, and 5« This probability was determined by statistical analysis of records of flood discharge of the Colusa Basin Drainage Canal at Highway 20 near Colusa. The gating station on the canal at Highway 20 measures all the flow from Reaches k and 5? and is considered to be representative of the flow continuing through Reach 3- 100 DISCHARGE OF COLUSA BASIN DRAINAGE CANAL AT HIGHWAY 20 NEAR COLUSA IN 1000 CFS Figure 3. FREQUENCY OF FLOODING IN REACHES 3, 4, AND 5 On February 21, 1958, the mean daily discharge of the Colusa Basin Drainage Caxial at Highway 20, was 23,900 second-feet. Because the channel capacity of the drainage canal in this vicinity is about 2,100 second-feet, flooding occurs when this flow is exceeded. There is suffi- cient slope in the drainage channel in Reach 3 that this reach is not influenced by backwater conditions prevalent in Reach 2. In Reach 2, the degree of flooding can be related more satisfac- torily to the water stage in the Colusa Basin Drainage Canal at the Knights Landing outfall gates than to flood discharge. Factors other than flood .^k- dischsirge from the tributary area have a marked effect upon the degree of flooding. A high stage in the Sacramento River and flov through the Yolo Bypass, combined with only a minor flood discharge from the tributary area, can cause backwater in the drainage canal and significant damage in this reach. The probability of annual occurrence of various sizes of floods in Reaches 1 and 2 in terms of gage heights of the Colusa Basin Drainage Csinal at the Knights Landing outfall gates is shown in Figure k. In the 1958 flood, the stage in the drainage canal reached a peak elevation of 36.? feet (USED datum). PROBABILITY OF ANNUAL OCCURRENCE IN PERCENT \ \ 25 30 35 40 45 GAGE HEIGHT OF COLUSA BASIN DRAINAGE CANAL AT KNIGHTS LANDING OUTFALL GATES (USED Ootum) Figure 4. FREQUENCY OF FLOODING IN REACHES I AND 2 Characteristics of Flood Hydrographs Flood hydrographs were prepared for the Colusa Basin to provide information relating to peak discharges, the time required for a flood to pass through the basin and total quantity of water involved in a flood. Basically, a flood hydrograph is prepared by plotting the acutal or estimated discharge of a stream at intervals of two to eight hours throughout the duration of the flood. The result is a graph, or pictiire, of the rise and fall of the stream as the flood passes a given point. This information was used primarily in designing works to alleviate flooding. -55- Typical flood hydrographs were developed for each of the tributary areas. Preparation of such hydrographs postulated quantities of flood runoff resulting from a uniform amount of precipitation on each watershed and used the pattern of the hydrograph experienced in the February 1958 flood. These synthetic floods were combined and routed through the existing channels to determine the extent of flooded areas possible under present conditions. Also, the same synthetic floods were combined and routed through proposed systems of protective works to determine the effectiveness of the proposed works. The same characteristics, or sequence of time and volume, of the typical hydrograph were assumed to prevail for all sizes of floods. Annual Distribution of Floods The seasonal variation in flooding was determined from ainalysis of historical discharges of the Colusa Bsisin Drainage Canal at Highway 20 and historical stages at the Knights Landing outfall gates. For this purpose, the year was divided into three time periods as an aid to the economic analysis of flood damage to crops. As previously stated, the greatest monetary damage occurs dur^'ng the spring floods. Tables h eind 5 show the amoimt of flooding during each of the time periods selected. Table k, representing Reaches 3, h, and 5, indicates that nearly all floods larger than 11,000 second-feet at the Highway 20 Bridge will occur during the period February 1 through March 31. However, eight percent of the floods smaller than 2,i+00 second-feet, including the spring drainage floods, will occur during the period April 1 through September 30. Table 5> representing Reaches 1 and 2, shows that nearly all flood stages higher than 35 feet (USED latum) in the Colusa Basin Drainage Canal at the Knights Landing outfall gates will occur during the two -56- TABLE k ANNUAL DISTRIBUTION OF FLOODS IN REACHES 3, ^, AND 5 Magnitude of flood, in second-feet :Time of year of flooding, Probable number: in percent of time of floods : April 1 :Oct. 1 : Feb. 1 per 100 years : through : through : through Sept. 30: Jan. 31: March 31 27,000 2 11,000 10 5,000 25 2,^4-00 50 - — 100 - 1 99 2 33 65 8 51 1^1 TABLE 5 ANNUAL DISTRIBUTION OF FLOODS IN REACHES 1 AND 2 Flood stage at Knights Landing outfall gates, in feet-^ Probable number: of floods :_ per 100 years : Time of year of flooding, in percent of time April 1 : Oct. 1 throLi gh : through Sept. 30: Jan. 31 Feb. 1 through March 31 39-5 2 — 23 77 35.2 10 1 28 71 32.5 25 3 39 58 30. J+ 50 7 i^5 48 * USED dat-om. -57- consecutive periods extending from October 1 through Kiarch 31- About seven percent of the floods reaching 30 feet will occur during the period April 1 through September 30. Extent of Flooding The extent of the area flooded in each reach at various discharges or water levels in the Colusa Basin Drainage Canal was determined through study of the records of historical flooding and of measurements taken from topographic maps. For each reach, the relationship between the proba- bility of aJinual occurrence, in percent, and the extent of the flooded area, in acres, was determined. Curves depicting this relationship are presented in Figure 5- For Reach 1, the northern Yolo Bj^-pass, Figure 5 depicts only those conditions existing during the period April 1 through September 30. Flood conditions in the bypass during the winter periods were not considered becaiise the bypass lands are established to convey winter flood waters. Flood Damages The probable frequency of flooding and the extent of the areas flooded in each of the reaches are measures of flood damage. However, economic evaluation of the proposed projects requires that damages be expressed in monetary values. The benefits derived from any flood control project are measured by the difference in monetary damages occurring before the project and those occurring after construction of the project. Interviews with about half the landowners in the areas subject to flooding provided detailed information on the extent and cost of flood damages experienced in recent floods. The area farmed by the landowners represented considerably more than half of the total flood area. Local officials, county farm advisors, representatives of irrigation districts. •58- REACH I REACH 4 5 10 15 20 25 FLOODED AREA IN 1000 ACRES 30 80 60 40 20 \ \ ^ -— 10 15 20 FLOODED AREA IN 1000 ACHES SO REACH 2 REACH 5 ao 60 40 20 \ , 10 15 20 FLOODED AREA IN 1000 ACRES 10 15 20 FLOODED AREA IN 1000 ACRES REACH 3 REACH LOCATION 1 NORTHERN YOLO BYPASS 2 KNISHTS LANDING TO COLLEGE CITY 3 COLLEGE CITY TO HIGHWAY 20 4 HIGHWAY 20 TO COLUSA-GLENN COUNTY LINE 5 COLUSA-GLENN COUNTY LINE TO WILLOWS 10 15 20 FLOODED AREA IN 1000 ACRES Figure 5. PROBABILITY OF FLOODING IN COLUSA BASIN AND YOLO BYPASS and others also cupplied information used by the Department of Water Resources to evaluate monetary damages . These damages are "based upon the price level of crops, their yield per acre, and associated costs of production that 1/ prevailed during the 5-year period from 1952 through 1956. In the predominately agricultural Colusa Basin area, most monetary flood damage occurs as crop damage; the rest, as miscellaneous damage to public and private facilities. Data developed by the U. S. Corps of Engi- neers shovred that, during the floods of February to June of 1958> damages to an area of 62,000 acres in the Colusa Trough amounted to $985^000, an average of about $l6 per acre. Crop Damage Crop damages are those losses directly caused by the flooding of agricultviral land. Crop damages can occur during every stage of plant development as well as during periods of land preparation prior to the actual planting of the crop. They include reductions in yield and quality resulting from plantings delayed by early floods or partially destroyed by floods of short duration, and losses incurred in replanting crops completely or partially destroyed by flooding. Both the loss of original expenses incurred in raising such crops, and the loss of income which would have been received from their sale contribute to crop flood damages. Estimates of damages in this investigation comprise only those that accrue to the primary producer, or farmer, but not to secondary processors. Crop damages vary greatly according to the time of year when flood- ing occurs. A relatively small flood during the growing season may cause 1/ The Department of Water Resources currently (1962) uses the 5-year period from 1952 through I956 as a base period for prices and costs in evaluating the economics of future agricultural development. -60- more crop damace than a large v;-inter flood. Table 6 shows estimated flood damages per acre to representative crops during three selected periods of the year. TABLE 6 ESTD-IATED CROP DAT'IAGE RESULTING FROM FLOODING IN REACHES 1, 2, 3, k, AND 5 (in dollars per acre) Time of year of flooding April 1 October 1 : February 1 Crops through througii : through September 30 January 31 : : larch 31 Truck crops Tomatoes $195.00 $3.80 $15.00 Beans 9^.00 2.00 5.00 Field crops Sugar beets li^6.00 3.00 35.00 Milo 65.00 2.00 4.30 Safflover 70.00 2.00 4.50 Rice * 5.80 5.80 Barley- 60.50 it-6.00 52.00 Alfalfa 83.00 5.00 31.00 Pasture 57.00 3.70 20.00 Double crops Beans -barley 59.00 44.50 50.50 Sugar beets - barley 65.00 50.50 56.50 Milo-barley U9.00 34.50 40.50 Rice -barley 50.20 35.70 41.70 * $46.00 per acre Reaches 1 and 2, in Reaches 3, 4, and 5; $92.00 per acre in For a flood of a particular magnitude, the weighted average annual damage per acre to each crop in a particular reach is the sum of the products for each period of the frequency of occurrence in the reach of that size flood and the damage to the crop. In Reach 3, for example, a -61- flood of a magnitude whose annual, frequency of occurrence is 25 percent would result in a weighted average annual damage per acre to beu:ley of $50.19. This figure was derived from Tables k and 6 as follows: Table k shows that of those floods in Reach 3 ^ose annxxal frequency of occurrence is 25 percent, two percent occur in the period from April 1 through September 30, 33 percent in the period from October 1 throxogh Jaaauary 31* and 65 i)ercent in the period from Febiniary 1 through March 3I. Table 6 shows that barley would sustain crop damage of $60.50 an ax:re, $i+6.00 an a^re, and $52.00 an acre, respectively, in the same three periods. The weighted average annua] damage per euire of barley, therefore, is the sum of two percent of $60.50, 33 percent of $U6.00, and 65 percent of $52.00. In a similar manner, the weighted average annual, daioage per 6u:re was developed for the range of flood sizes which could affect e£u:h crop which might be grown within the sireas subject to flooding. After having established crop damsige per acre, it became necessary to determine the present and predicted futvire acreage devoted to each crop. The product of crop damage per acre and the acreeige devoted to eauch crop equals the total damage to each crop. This total damage was computed for various sizes of floods. The crop pattern of crops flooded in any peurt of a reach was assumed to be the same as that in the entire reach. The present pattern of crop acreage in each reach was determined by appropriately adjusting data provided by a land use survey made in 195^ for Department of Water Resources Bulletin No. 58, "Northeast Counties Investigation." Estimates of the crop pattern as it would be in the futtire without additional flood protection were based upon the soil types in eeu:h reach, the suitability and adaptation of certain croi>s to each reach, and -62- the anticipated econcjmic trends SLffecting each reach. !Hie crop pattern was assvoned to change from the existing to the future pattern uniformly in the first ten years and to remain constant thereafter. Table 7 sumnarizes the net eicreage devoted to each crop within each reaujh vmder existing and predicted future conditions without additional flood protection. Lands now used as himting areas for gun clubs are assumed to continue in the same category in the future. Figure 6 shows graphically the probability of present and future crop damEiges, in Reaches 2, 3> ^t Bnd ^, resulting from various sizes and frequencies of floods. The frequency- damage relationshii>s depicted in this grax>h were used to detemiine an estimated average euiniial equivalent crop damage for a 50- year period. This crop damage, as it would occur with- out construction of flood protection works, averages $150,000 a year. This amount does not include crop damages trtiich would occur in the area along the Colusa Basin Drainage Canal for which a flood eausement would be purchased in connection with flood protection works discussed in Chapter k. Miscellaneous Damage Miscellaneous damage Includes damage to such public feu:ilities as highways, roads, communication systems and irrigation works, damage to such private facilities a^ pumping plants, irrigation euid drainage systems, fences, farm eqvilpment, and personal property; damage from weed infestations resvjlting from weed seeds carried by flood waters; and damage to area^ used for waterfowl management and by duck clubs. Public and private facilities subject to flooding within the Colusa Basin area sjre few, however. A significant euaount of miscellaneous damage is physical damage to property used in waterfowl maneigement and to property belonging to duck clubs. This damage was estimated at three dollars -63- on CO Lr\ « 0) "I O I on I • I I I i I 0.0 ^ I I I I I I 31 o o 8.1 CO fio o o m LA Q I O a\ I CO o I vo I cvj cu O 2^&i 831 LTV ir\ ( S88 CO LA ITS I O H H H I O < 8 8 3 S 1 O I C3\ O o fO o CVI LfN cu a Lf\ « VO o Lf\ 0) o 8 H CVJ o o Ed o oo o o 00 t~- Si. m vo Ed Ed lA lA •\ CVJ H o o !;f^ H C^ lA CVJ H CO CO H CO J- ?> H 8 CVJ lA 9s CVJ lA CO CO H f^ p^ 8 0\ 8 I H U T) i I s d I m <; ft -6U- \ 3 \ \ \ \ \ \ \ \ \v -FUTURE -PRESENT \ \ \ x^ \ \::^ (0 20 30 40 50 60 70 PROBABILITY OF ANNUAL OCCURRENCE IN PERCENT 80 90 100 Figures. PROBABILITY OF CROP DAMAGES IN REACHES 2,3, 4, AND 5 a year per flooded acre. No monetary value was placed on damage to recreation enjoyment through the loss of hunting opportunity. A reasonable analysis of this type of damage was not possible with the meager data avail- able. Although this loss is significant in some years, qualitative studies indicate that it becomes only slightly significant when reduced to an annual probability of occurrence during the legal hunting season. Although floods interfere with hunting opportunity, the waterfowl population benefits from the increased resting and feeding areas available to it during floods. Field surveys and studies by other agencies provided the data required to obtain estimated miscellaneous damages resulting from several recent floods. After these damages were plotted on a graph according to the frequency of occurrence of the size of flood Involved, a projection was made of flood damages for a full range of flood sizes. Figure 7 graphically summarizes the magnitude of miscellaneous damage expected for floods of variolas probabilities of occ\irrence. Without additional flood protection, an estimated average annual equivalent miscellaneous damage of $46,000 would occur during a 50-year period in Reaches 2, 3j 4> and 5« Table 8 summarizes flood conditions and flood damages in the Colusa Beisin under present conditions of development. -66- 3 2 10 20 30 40 50 60 70 PROBABILITY OF ANNUAL OCCURRENCE IN PERCENT 80 90 100 Figure 7. PROBABILITY OF MISCELLANEOUS DAMAGES IN REACHES 2,3, 4, AND 5 TA3LE 8 FLOOD CONDITIONS AND PRESENT FLOOD DAMAGE IN REACHES 2, 3, U, AND 5 Estimated flood conditions : Flood discharge Probability: of Colusa Basin of annual : Drainage Canal at occurrence,: Highway 20 Bridge, in x^rcent : in second-feet Gross flooded area, in acres Estimated flood daciage, in dollars* Mlscellajieous: Crop damage : damage : Total 2 25,000 5 18,000 10 11,000 20 6,000 30 U,000 uo 3,000 50 2,U00 83,000 2i+6,000 700,000 9^6,000 65,000 190,000 )i8o,ooo 670,000 1+9,000 136,000 380,000 516,000 32,000 85,000 25^,000 339,000 23,000 56,000 167,000 223,000 17,000 33,000 105,000 138,000 13,000 17,000 6i+,ooo 81,000 *For the purposes of subsequent project analysis, these estiinates do not include flood damage on i4-,600 acres of lajid along the Colusa Basin Drainage Canal that would be within the flood channel, if a levee project were built. -68- CHAPTER IV. POSSIBLE SOLUTIONS In this investigation the following four possible solutions to flood problems of the Colusa Basin were considered: (1) systems of levees along the Colusa Basin Drainage Canal; (2) flood control reservoirs in the western foothills; (3) watershed management; and (4) improved drainage facil- ities from the Knights Landing Ridge Cut through the Yolo Bypass. These plans were designed to operate without interference to water rights or diversion of waters from drainage channels in the Colusa Basin, Detailed engineering studies and economic analyses showed that levees constructed along the Colusa Basin Drainage Canal would not be econom- ically justified. Three such projects, the Colusa Basin Levee Projects, are summarized in this chapter. Additional details of the investigation are on file at the Department of Water Resources. The investigation of flood control reservoirs in the western foot- hills, the Foothill Reservoir Project, was conducted to the point where it became apparent that the prpject would be more costly than any of the Colusa Basin Levee Projects. This chapter summarizes data developed during the investigation. Limitations of time and funds permitted only brief consideration to be given to practices of watershed management which might minimize flood problems of the Colusa Basin, Such consideration as was given is summarized in this chapter. The construction of improved drainage facilities in the northern portion of the Yolo Bypass proved to be an economically justified solution to problems created by limited flood volumes in a limited area. This project, the Yolo Bypass Project, was thoroughly investigated. The results of this investigation are described in this chapter, -69- Col\i3a Basin Levee Projects Each of the Colusa Basin Levee Projects vould consist of a contin- uous system of levees on both sides of the Coltisa Basin Drainage Canal frcan Knights Landing to the canal's junction vith Willow Creek and along Willow Creek to a iwint near Willows. The canal itself wo\Jld continue to function as the main drainage channel of the Colusa Basin. The main flood channel within the basin wotild be that formed by the existing csj^al suid an area vai^-ing from 1,000 to k^O feet in width between the levees. Additional levees to be constructed along streams tributary to the canal would convey flood flows into the cajial. Such suidltional levees would continue up the tributary streams to the limit of the backwater influence of the main flood channel. Drainage water from the areas protected by these levees would be conveyed into the Colusa Basin Drainage Canal either by gravity or by pumps. Facilities for drainage from areas lying outside the present flood plain would not be included as part of the levee projects. The Colusa Basin Levee Projects would provide flood protection to Reaches 2, 3, k, and 5, but would not extend into Reach 1. Within design limits, therefore, they would protect lands in the beisin presently subject to flooding. The largest levee system — the Two Percent Projecti/ — would provide protection from project design floods reaching a magnitude of 27,000 second- feet as measured at the Highway 20 Bridge neeur Colusa. Smaller levee systems, the Five Percent and Ten Percent Projects, would provide protection from project design floods reaching magnitudes of 1/ The term "two percent" refers to the size of flood that woiald be eqiialled or exceeded two perx:ent of the time or an average of once-in-50- years. Similarly, a five jjercent flood would be equalled or exceeded once-in-20- years; and a ten percent flood, one e-in-10- years. ■70- 22,000 and 15,300 second- feet, respectively, at the same point. Becavise the projects would confine flood waters to the leveed channels and prevent temporary storage on flooded areas, project design flood discharges wovild be greater than pre-project flood discharges. Each size of levee project wo\ild ccsnprise li4-2 miles of new levee construction. In the southern portion of the area, between Knights Landing and a point k miles soxith of Coliisa, the existing back levee of Reclamation District No. 108, which is part of the Sacramento River Flood Control Project, would constitute the east levee of each of the Colusa Basin Levee Projects. Only the west levee would be new along this stretch. To allow for the passage of project design floods, the west levee for its entire length would be placed some distance frcsn the Colusa Basin Drainage Canal. Proposed flood chaimel widths of about 1,000 feet in the southern part of the project may be ccanpored with the present drainage channel width of about 200 feet. Table 9 shows the channel width and design discharge at various points for each of the three projects. Plate 5, "Profile and T/pical Sections of Colusa Basin Levee Projects," shows typical cross sections emd water surfeuie profiles of the three projects. Levee and channel design stajadards conform to those of the U. S. Corps of Engineers, Sacramento District. The levees would vaxy in height from about I8 feet in the south to 11 feet in the north and would provide 3 feet of freeboard at design flood stage. The levee embanianent would be constmcted with side slopes of 3 to 1 on the waterside and 2 to 1 on the landside. A berm 20 feet wide was provided between the waterside toe of the levee and the edge of the low water channel. From the soxithern terminus of the system at Knights Landing Ridge Cut north to Highway 20 near Colusa, levees along the Colusa Basin ■71- a •H +3 0) tw ^^ X) 5§ o o ■H in a 0) Cm o •H 8 8 u\ iTi ^ ^ o o on H o CO H O 8 m o en 3 CO H O cn H O m 8 + m -p I H 0) ro O cn UN 8 8 8 8 ro on o O LfN Lr\ VO M3 Ed ^ o 8 o LfN ON CM CM O CJN cd Lf\ cu CM KT VO on cu o On cy s K OS •H U CQ a* •H K O H s (d >i 9 ^ ■^ •§, o a Vl « (U « a a n O u CJ 3 t H -P I -H 4> CJ ■P d a; (30 tlO H 4) ^? VD H on O ^ d H CO H CO H 8j ^ 8 8 ^- o CO O CO 8 8 8 8 8 8 + + + + + + CVJ CM CO H CM H CO 4* O I OS o 01 O Ci •H CO f-I CM ^ ^ + o a a ■p ^ Drainage Canal woiild have a crown width of 20 feet. Further north and along all tributary channels, their crown width would be 12 feet. The new levees of any of the three Colusa Beisin Levee Projects would block drainage from the lands that the levees would protect. New drainage facilities would be required to remove water from the protected areas. Such facilities would consist of improved farm drainage works, coJJLector drains, and pumping plants. Construction of improved farm drainage works would be the responsibility of individvial landowners. The tsLrm. drains would convey water to project-built collector drains, 6 to 8 feet deep, which, in turn, would carry the water into the Colusa Basin Drainage Canal. Project-built pumping plants would pump water from the collector drains into the canal during its high water periods. During low water periods, water from the collector drains would flow directly into the canal. The largest of the Colusa Basin Levee Projects, the Two Percent Project, would include a flood retention reservoir just north of Majcwell Roewi at the confluence of Stone Corral Creek and the drainage csuial. Two miles of low dike on its perimeter, as well as a portion of the new levee, would confine the reservoir to 2,100 acres. The reservoir would have a storage capacity of l6,000 acre- feet. Whenever discharge near Colusa would exceed 20,000 second- feet, a specially designed concrete weir in the main levee would permit excess flows from the drainage channel to enter the flood retention reservoir. By reducing the peaks of the very large floods, this reservoir woiold allow the use. In the lower portion of the project area, of a smaller flood channel than would otherwise be possible for the same level of flood protection. The Two Percent Project wovild protect about 80,000 acres of Colusa Basin lands which have flooded in recent years. The project would handle -73- floods whose magnitude, without the flood retention reservoir, would be 27,000 second-feet sis measvired at Highway 20 Bridge near Colusa. A comparable flood under present conditions would discharge about 25,000 second- feet at Highway 20. Under present conditions, the flow is decreased somewhat by storage In flooded areas, whereas under project conditions the entire flood runoff woiild be channelized. The flood retention reservoir would reduce floods of this magnitude to 18,000 second- feet at Highway 20. Project design would provide complete protection from the once-ln-50-ye8j: flood and would reduce the acresige affected by larger floods. The Five Percent Project would have a design capacity of 22,000 second- feet as measxired at the Highway 20 Bridge. A flood of this size, occurring under present conditions, would discharge about 18,000 second- feet at Highway 20. Project design for this flood was based upon complete channel- ization of the flows without a retention reservoir. Complete protection would be afforded to lands subject to overflow from the Colusa Ba^in Drainage Canal for floods up to the design capacity. This capax:ity approximates a flood with a probability of once-in-20-year occurrence, or about the size of that which occurred in February 19'+2. The Ten Percent Project would have a design capacity of 15,300 second- feet, measured at the Highway 20 Bridge. A flood of this size, occurring under present conditions, would discharge about 11,000 second- feet at Highway 20. Project design would provide complete protection to lands subject to overflow from the Colusa Basin Drainage Canal from floods up to the magnitude of a once- in-10- year flood. This size may be compared to a flood smaller than that of February 19^+2, but larger than that of March 191+9. .Jh. Estimated Costs The estimated capital cost of each project includes costs of con- struction, costs of acquiring flood easements and rights-of-way, ajid costs of relocating public and private utilities. Capital costs were based on unit construction prices prevailing in the spring of I96I. Capital costs include allowances for contingencies, engineering and administration. Capital costs also include allowances for interest during construction at the rate of four percent a year for one-half the construction period, Anntial costs include costs of replacement, operation, maintenance, and general expense. They include interest on the capital investment and repayment over a 50-year period at either k or 2-5/8 percent a yeax. The four percent rate is assumed to be applicable to construction by a local public agency; the 2-5/8 percent rate, to construction by an agency of the United States. G?able 10 shows the estimated capital cost of each of the Colusa Basin Levee Projects, and Table 11, the estimated annual cost of each. Project Benefits The three projects would provide ccmplete protection from floods whose pre-project magnitudes would reach 25,000, 18,000, and 11,000 second-feet, respectively, as measured in the Colusa Basin Drainage Canal at Highway 20 Bridge near Colusa. Floods of this magnitude represent the once- in- 50- year flood, the once-in-20 year flood, and the once-in-10 year flood. Flood discharges greater than those for which each project was designed would continue to flood Colusa Basin lands, but to a reduced extent. In general, proposed levees west of the main flood channel would be lower than those on the east. Overtopping the west levees woxild not ca\ise general ■75- T/VHLE 10 ESTIMATED CAPITAL COSTS OF COLUSA BASIN LEVEE PROJECTS (In dollars) : Two Percent : Five Percent : Ten Percent Item : Project : Project : Project Construction items Einbanlonent Main channel 6,958,000 6,131,000 5,1+80,000 Tributary channels 1,1+61^,000 1,1+87,000 1,273,000 Road ai>proaches 1M*,000 11+3,000 11+0,000 Patrol roads 79*+, 000 785,000 775,000 Clearing aoad grubbing 215,000 216,000 172,000 Drainage channel excavation 316,000 316,000 316,000 Drainage pumping pleuats 5,389,000 1+, 390,000 3,635,000 Lands and Deunages Levee rights-of-way 392,000 358,000 31+8,000 Main channel 308,000 326,000 303,000 Tributary channels Flood easements 915,000 91+5,000 630,000 Main chajinel 10l4-,000 Flood retention reservoir 516,000 1+88,000 38i+,000 Acquisition costs (30^) Relocations Bridges emd roeuSs 1,163,000 1,093,000 81+8,000 Irrigation and drainage structures 528,000 516,000 516,000 Power and telephone lines 100,000 100,000 100,000 Gates 29,000 28,000 28,000 Subtotal 19,335,000 17,322,000 11+, 91+6,000 Contingencies (20^) 3,867,000 3,1+61+, 000 2,989,000 Engineering and administration (10^) 2,321,000 2,078,000 1,791+, 000 Interest during construction (l*-^) 510,000 1+58,000 395,000 Total capital costs 26,033,000 23,322,000 20,126,000 .76- ^ m I -p ■p CO V u 0) +> an O fa „ +> *R. OB I -P ^^ 4) a> -p o o U 0) 0) -O Ph o o a. i -P 0) CO ON CM 0\ LTN H on CO CM ro ir\ ITN Ov H ro CO CO l/N M3 CM Fi cS o •H ^ -P cn •p 4) •POO) CO H gflg g^ -77- flooding because flood waters then wovLLd be confined to the axea between the levees along tributary streams at the north and south ends of the area affected. The effect of siich overtopping would be to reduce the flood stage in the main flood channel and to lessen the flood hazard to areas downstream. The cognparison of estimated flood damage to Colusa Ba^in land before and ai"ter construction of each of the Colusa Basin Levee Projects permitted the evaluation of the accomplishments of each project. The effect on each of the projects of flood sizes exceeding project design floods was calculated in terms of the extent of area which would be flooded. Statistical analysis of aureas subject to flooding enabled the preparation of graphs showing the probability of occurrence of various sizes of floods and the extent of the area flooded by eax:h size under project conditions. The method of auaalysls was similar to that used to detennine probability of occurrence under pre-project conditions. The graphs in Figure 8 depict conditions of flooding in Reaches 2, 3> ^} and 5 with smd without the Colusa Basin Levee Projects. Average annual primary benefits directly attributable to the Colusa Basin Levee Projects resvilt frcm reductions in crop and miscella- neous damsiges as well as from enhancement to eigricultural and urbsji lands in the four reaches included in the project. Table 12 itemizes these benefits. A disc\xssion follows of the methods by which such benefits were computed. Crop Damage Reductions . A method similar to that discussed in Chapter lU to determine average anniwl equivalent crop damage without a project was vised to compute such damage under project conditions. The method utilized data developed frcm the relationship between crop damage in Reaches 2, 3, ^, and 5 and the probability of annual occurrence of ■78- REACH 2 REACH 4 ^lOf. PROJECT /^¥-b1. PROJECT V/^// 2% PRpjECT 5 10 15 20 25 30 FLOODED AREA IN 1000 ACRES 100 5 40 V V r— WITH PROJECTS / 1 ^r— WITHOUT PROJECTS < ^107 PROJECT 1 "--v^ 5% PROJECT "^ ^ --_ ^^ 5 10 15 20 25 FLOODED AREA IN 1000 ACRES 30 REACH 3 REACH 5 \ \ k \ -WITH 2% WITHOL 5%, and 1 T PROJEC D% PROJE TS CTS V \/ ^ TH PROJE( ITS WITHOUT PROJECTS / PROJECT Z1. PROJECT -Z^^ V '■• -S2^^ 5 10 15 20 25 30 FLOODED AREA IN 1000 ACRES 10 15 20 25 FLOODED AREA IN 1000 ACRES REACH LOCATION KNIGHTS LANDING TO COLLEGE CITY COLLEGE CITY TO HIGHWAY 20 HIGHWAY 20 TO COLUSA-GLENN COUNTY LINE COLUSA-GLENN COUNTY LINE TO WILLOWS Figure 8. PROBABILITY OF FLOODING IN COLUSA BASIN WITH AND WITHOUT THE COLUSA BASIN LEVEE PROJECTS TA.BLE 12 ESTIMATED ANNUAL BENEFITS OF COLUSA BASIN LEVEE PROJECTS (in dollars) Type of benefit : Two Percent : Project : Five Percent Project : Ten Percent Project Damage prevention Crop dBinage Miscellemeoiis damaige lM+,000 U.lt,000 139,000 1+3,000 13i+,000 1+2,000 Subtotal 188,000 182,000 176,000 Land enhancement Agricultural Urban 368,000 22,000 368,000 368,000 Subtotal 390,000 368,000 368,000 Total annual benefits 578,000 550,000 5i+l+,000 various sizes of floods in these reaches. This relationship is shovm in Figure 9 under conditions with and without the Colixsa Basin Levee Projects. Without a project, the average annual equivalent crop damage would amount of $150,000; with the Two Percent Project, such damage woxild amount to only $6,000. The annual amount of damages reduced by the project, $lM+,000, represents the average annual crop damage prevention benefits of the Two Percent Project. Slmil£u:ly, average ann\ml crop damage prevention benefits for the Five Percent and Ten Percent Projects were estimated to be $139,000 and $13!+, 000, respectively. Miscellaneous Damage Reductions . A method simileir to that developed in Chapter III to determine average annual miscellaneoua damages without a project was used to compute such damages vinder project conditions. -80- \ \ \ \\ \ \\ » \ \ ITHOUT PR OJECTS -FUTURE -PRESENT \ \ \ \ Xx \\ \ WITH COLUSA B JEE PROJE ASIN ^ :ts X :^. WW a FUTURE L^ \W -5% PROJEC T, FUTURE >JT T, PRESENT — 2% PROJEC 20 30 40 50 60 70 PROBABILITY OF ANNUAL OCCURRENCE IN PERCENT 80 90 100 Figures. PROBABILITY OF CROP DAMAGES IN REACHES 2, 3, 4, AND 5 WITH AND WITHOUT COLUSA BASIN LEVEE PROJECTS The method utilized data developed from the relationship between miscel- laneous damage in Reaches 2, 3j ^, and 5 and the probability of ajmual occurrence of various sizes of floods in these re£u:hes. This relationship is shown in Figure 10 under conditions with and without the Colusa Basin Levee Projects. Under existing conditions, without a project, the average annual miscellaneous damage was estimated to be ^k6,000; with the Two Percent Project, such damage would amount to only $2,000. The annual amount of damEige reduced by the project, $^+4,000, represents the average ann\ial miscellaneous damage prevention benefits of the Two Percent Project. Similarly, average annual miscellaneous damage prevention benefits for the Five Percent and Ten Percent Projects were estimated to be $1+3,000 and $42,000, respectively. En ha n cement to Agricultural Lajids . Significsmt benefits would result from the possibility of a more intensive use of sigrlcxiltural lands under project conditions. The future ci^ap pattern would include more of the higher paying truck and field crops and the use of lands now idle would increase the total crop area. Such benefits were measured sis the difference between returns to the land with and without each of the Colusa Basin Levee Projects. The average eumual benefit from more intensive use of agricultural leuids was estimated to be $368,000 for each of the levee projects in the four reaches affected by the project. Enhancement to Urbeui Lands . Under the level of flood protection afforded by the Two Percent Levee Project about 1,500 additional acres in the Colusa Basin wovild be subject to urban development. This gunount includes about 800 acres near Willows, 120 acres at Delevan, 300 acres at -82 WITHOUT PROJECTS \ I WITH P ROJECTS \ •^ w — 10% PROJ — 5% PROJ ECT ECT ECT -- H \ 10 20 30 40 50 60 70 PROBABILITY OF ANNUAL OCCURRENCE IN PERCENT 80 90 100 Figure 10. PROBABILITY OF MISCELLANEOUS DAMAGES IN REACHES 2,3,4, AND 5 WITH AND WITHOUT COLUSA BASIN LEVEE PROJECTS Colusa, eind 320 acres at Knights Lajiding. Such an increase in habitable areas protected from floods is a project benefit. Assuming progressive urban development of these lands throughout a 50-year period, the average ajinual urbem benefit for the four reaches affected by the Two Percent Project was estimated to be $22,000. This benefit was based on the increase in returns to the lemd measured at five percent per year of the increased capital value of the land. The two pro- jects of lesser protection would afford insufficient protection to induce urban land use and consequently, no enhajicement benefits would be derived. Econanic Justification Before a public agency can consider construction of a flood control project, that project must be economically jiistified. To be economically justified, a project must have primary benefits which exceed project costs. The prim6u:*y benefits from any of the Colusa Basin Levee Projects do not exceed the respective costs of each project. Table 13 shows this to be the ca^e whether the interest rate is that assumed applicable to construction by a local public agency or that assumed applicable to construction by an agency of the United States. For the present level of developoient in the Colusa Basin, therefore, a levee project would not be economically justified. A complete economic aumlysis would require a determination of the benefits or detriments accruing to the project as a result of its effect on fish and game. Wildlife studies were conducted during this investigation only at a reconnaissance level to determine the usage of leuid within the historically flooded area for migratory waterfowl habitat. From this brief survey it whis assumed that construction of a flood control and drainage pro- ject in the Colusa Basin would adversely affect waterfowl habitat. A -81+. detailed determination of iwssible detriments, or benefits, was omitted because the project was shown to be not justified on the basis of priraaiv agriciiltural suid vtrban benefits. TABLE 13 COMPARISON OF ESTIMATED COSTS AND BENEFITS OF COLUSA BASIN LEVEE PROJECTS : Two Percent : Five Percent : Ten Percent Item : Project ; Project ; Project Annual costs, in dollars k-<^ interest 1,771,000 1,5^9,000 1,36'5,000 2-5/8^ interest 1,H0,000 1,306,000 1,155,000 Ann\ifl1 benefits, in dollars 578,000 550,000 5^,000 Benefit-cost ratio k-fi interest 0.33 O.36 0.1*0 2-5/89^ interest 0.1^0 0.1i-2 O.I4-7 Foothill Reservoir Project The 8u:ea contributing flood runoff to the Colusa Basin Drainage Canal covers about 1,500 square miles. Of this area, 570 square miles comprise the tributary watershed in the eastern foothills of the Coast Range and the remal ning 930 square miles lie within the relatively flat Sacramento Valley. During major storms in this drainage area, more precip- itation falls in the foothills than in the valley. Dams constructed swiross the streams of this foothill watershed would create reservoirs whose temporary storage of flood runoff woxild reduce flood discharge in the Colusa Basin Drainage Canal. An investigation was made to determine the degree of flood control that a series of reservoirs woixld provide. Control of the entire watershed would require dams on 67 streams. However, dams on I7 of the larger streams would control a watershed of -85- USO square miles, about 80 percent of the foothill drainage area. These 17 dams are described in this section as the Foothill Reservoir Project. A reconnaissance engineering survey was made to determine the cost of the project and the degree of pi"otection it would provide. The Foothill Reservoir Project was designed to control floods with a probability of occurrence of two percent, or floods whose magnitude is that of the once-in- 50-year flood. Flood hydrogi-aphs ajid the magnitude of flood flows at the reservoir sites were developed from data used to determine the contribution of the tributary streams to flood flows in the Colusa Basin Drainage Canal. The storage capacity of each reservoir was selected for purposes of flood control only and vithout consideration of water conservation or other purjoses. Reservoir capacity at each site would be sufficient to store runoff without outflow for the dviration of high flood inflows to the reservoir. Outlet works were designed to release the stored water rapidly so that each reservoir would empty and be ready to control the next flood peak occurring on the tributary. Releases would not be permitted to exceed the capacities of dovmstream channels, and wovild be timed to enter the Colusa Basin Dreiinage Canal after the peak flood flow in the canal had passed well downstream. Preliminary designs and cost estimates were prepared for each of the 17 danis and reservoirs with consideration given to the geology of the site, the availability of construction materials and engineering standards for the safety and operation of the project. The total capital cost of the Foothill Reservoir Project was estimated to be about $28,760,000. For each dam and reservoir. Table Ik gives the capital cost, drainage area, storage capexiity, and flood discharge under conditions of the once- in- 5O- year flood. Tables I5 and 16 show probable conditions during a once-in-50-yeeu' -86- TABLE Ik SUMMARY OF FOOTHILL RESERVOIR PROJECT Reservoir location Drainage area above dam site, in square miles Reservoir storage capacity, in acre- feet Once- in- 50- year flood discharge, in sec ond- feet Uncontrolled : Controlled^/ rfilson Creek 13.5 French Creek 69.2 Unnamed Creek I3.7 South Fork Willow Creek 79. Logan Creek 20. U Hunter Creek I5.8 Funks Creek 14.7.5 Stone Corral Creek 36,5 Freshwater Creek 32.8 Salt Creek 10. 5 Spring Creek I6.9 Cortina Creek 33,5 Salt Creek I8.9 Petroleum Creek 6.0 Buckeye Creek 31. 3 Bird Creek 8.0 Oak Creek 27. U8O.5 2,200) ) 11,000) ) 2,200) ) ) 12,600) 3,300) ) 2,500) 7,600) ) 5,800) 7,000) 2,700 5,300 3,000 1,000 5,000 1,300 ^,300 76,800 l6,ivoo 3,500 3,900 8,300 i^,300 1,700 3,^00 1,900 600 3,100 800 2,700 Capital costs of dain and reserv^olr, in dollars 1,305,000 3,865,000 1,619,000 2,1+52,000 550 888,000 1,088,000 900 1,516,000 1,317,000 51*0 1,414,000 392,000 200 2,205,000 k^O 2,760,000 250 2,082,000 60 1,212,000 350 2,200,000 150 1,040,000 350 1,405,000 _--- 28,760,000 \y Controlled release following y Salt Creek Dam diverts up to flood. No releases made during high flood inflow. 1,000 second- feet into Freshwater Creek Reservoir. -87- TABLE 15 PROBABLE DISCHARGE DJ WILLOW CREEK AWD THE COLUSA BASIN DRAINAGE CPJiPdj DURING A ONCE- IN- ^0- YEAR FLOOD (In second- feet) Location With Foothill Reservoir Project With Two Percent Colusa Basin Levee ProjectV Without either project Willow Creek at Glenn-Colxisa Irriga- tion District Canal crossing nesur Willows 6,200 Colusa Basin Drainage Cemal at Highway 20 Bridge nesir Colusa 9,600 at Knights Landing 13,200 1/ Without flood retention reservoir 2/ Maximum mean daily flow, 1958 17,000 27,000 31^,000 23 ,90oS/ TABLE 16 PROBABLE FLOODED AREAS IN REACHES 2, 3, ^, 5, and 6 DURING A ONCE- IN- 50- YEAR FLOOD (In acres) Reach With Foothill Reseirvoir Project With Two Percent Colusa Basin Levee Project Without either project 6 - Northwest of Willows 17,500* 17,500 5 - Willows to Glenn- Colusa coxinty line 6,500 15,000 k - Glenn-Colusa county line to Highway 20 19,000 U0,000 3 - Highway 20 to College City 5,800 10,600 2 - College City to Knights Landing 17,000 21,000 l»-8,300 17,500 lOi+,100 * Levee project does not extend into Reach 6. -88- flood with and without either the Foothill Reservoir Project or the Two Percent Colusa Basin Levee Project. Table 15 shows probable conditions in terms of discharge in Willow Creek and the Colusa Basin Drsd-nage Cajaal. Table l6 shows the probable flooded areas in Reaches 2 through 6. Reach 6 was not included within the eirea to be protected by the Colusa Basin Levee Project. The accomplishments of the Foothill Reservoir Project may be evaluated by comparing the degree of flooding expected under project conditions to that which would occur both londer pre-project conditions and under conditions which would be created by the Two Percent Colusa Basin Levee Project. During a flood of the once-in-50-year magnitude, the most favorable operation of the foothill reservoirs would reduce the peaJc flow in the Colusa Basin Drainage Canal to 9j600 second- feet at the Highway 20 Bridge. Under pre-project conditions dviring a flood of the same magnitude, discharge at the same point would have been 25,000 second- feet. Correspondingly, operation of the foothill reservoirs would reduce to kQ,300 acres a flooded area •vrtiich under pre-project conditions would have been 10U,100 acres. During a flood of once- in- 50- year magnitude, the Two Percent Colusa Basin Levee Project would completely alleviate flooding in Reaches 2, 3, k, and 5 of the Colusa Basin, whereas, the Foothill Reservoir Project would allow flooding of 14-8,300 acres in those reaches. However, flooding of 17,500 acres in Reach 6 north of Willows would be prevented by the reservoir project but not by the levee project. An evaluation of the economic justification of the Foothill Reservoir Project would require that project costs be compared to project benefits as computed by determination of the reduction in flood damages -89- in the area protected by the project. Because it can be seen by comparing flooded areas that the benefits from the Foothill Reservoir Project woiold not be as great as those from the Two Percent Project, this computation was not made. For the Foothill Reservoir Project to provide the same degree of protection as that provided by the Two Percent Project, a system of low levees along the Colusa Basin Drainage Canal would have to be built. This additional construction would raise the cost of the reservoir project considerably above that of the Two Percent Project. Jtirthermore , despite the greater benefits and the lower cost of the Two Percent Project, the Two Percent Project has been shown not to be economically justified. It may be concluded, therefore, that the Foothill Reseirvoir Project also is not economically justified. Watershed Management Runoff from a watershed, measured as the difference between precipitation and infiltration, is influenced greatly by the retentive characteristics of the watershed. If the infiltration rate C£ui be increased by watershed management, the amount of runoff contributed to downstream flood flows can be reduced. Runoff from the foothill drainage area makes the major contri- bution to flood flows occurring in the Colusa Basin. Detailed analyses of a number of small-to-medium storms experienced in this area indicate that for a given storm the soil absorbs a large quantity of water before ajiy runoff occurs. This absorption is called the initial loss. As the soil becomes saturated, the infiltration rate decreases and becomes quite low. The average infiltration rate in the foothill drainage area for the ten hours after initial loss was estimated to be O.O5 inches an hour. -90- The "Hydrology Handbook," prepared by the Committee on Hydrology of the Hydraulics Division of the American Society of Civil Engineers, and adopted Jajiiiary 17, 19^9, cites studies which Indicate that such an infil- tration rate can be increased two to three times by improvement of the watershed. Watershed management experiments in simHar foothill regions show that the infiltration rate can be increased considerably by improving the grass cover, by converting chapetrrel areas to grass covered areas, amd by improving grazing practices. It can be estimated that if the foothill drainage area infiltration rate of O.O5 inches an hour were doubled within a 25-sqxM.re mile area in the foothill watershed, the reduction in runoff from that area could be as great as 8CX) second- feet. Were watershed management to duplicate such reductions in runoff throughout the foothill drainage area, flood discharge throiigh the Colusa Basin Drainage Cajial would be greatly reduced. The reduction In flood discharge would not equal the sum of the reductions in runoff effected by watershed management becaxise the runoff from various tributary watersheds would reach the drainage cana3. at different times. Kie effectiveness of watershed management for the purpose of flood control would be lessened during extended periods of rainfall or In rei)eated storms. Beca\ise of limitations of time and fvinds, field studies of water- shed management practices were not maxle as part of this investigation. Such studies would be of great value to future evaluations. Much time and experimental work would be requiired before conclusive results could be re8w:hed. These results might well indicate a relatively inexpensive n*ethod of reducing flood discharge. Such a method, however, would have to be coupled with some levee works in the valley area to provide flood protection compajrable -91- to that provided by the levee projects previously discussed. Adequate control of flood waters by watershed management only is considered highly improbable . Yolo By33asn Project The Yolo Bypass Project would improve existing draineige facilities within the Yolo Bypass. The project is designed to alleviate springtime crop and miscellaneous damages caxised principally by irrigation return flows flooding Reaches 2 and 1. Reach 2 extends along the Colusa Basin Drainage Canal from College City to Knights Landing. Reach 1, within the northern Yolo Bypass, extends southward from the mouth of the Knights Lemding Ridge Cut to the Sacramento Deep Water Ship Channel. In the spring, high water in the Sacramento River prevents irri- gation return flows frcm passing through the Knights Landing outfall gates into the river. At the same time, the inadeuqate outlet at the downstream end of the Knights Landing Ridge Cut impedes water passing through the ridge cut into the Yolo Bypass. Before the water reaches aui elevation sufficient to discharge into the bypass, it has flooded lands in Reach 2. Water passing through the ridge cut into the bypass causes additional dajiage by flooding early jilsuitings in the bypass farm lands of Reach 1. The Yolo Bypass Project wovild correct this situation with a new channel from the downstream end of the ridge cut. Under conditions of no flow in the Yolo Bypass, drainage facilities of the project would prevent flooding of farm lands in Reaches 1 and 2 when discharges from the ridge cvtt did not exceed 2,000 second- feet. During floods in excess of this design capacity, flooding in Reaches 1 and 2 would be reduced both in extent and duration. -92- From October 1 through Maxch 31? the drainage facilities of the Yolo Bypass Project vould have only very limited effect because the Yolo Bypass us'jally would be carrying winter flood waters from the Sacramento River at the same time that runoff from the Colusa Basin would be high. Altho\igh project facilities are not designed si)ecifically to fvinction under such conditions, they would provide some relief from flooding in Reach 2 at times when flows through the bypass were relatively small. The drainage facilities provided by the Yolo Bypass Project would include: (l) a check structure at the downstream end of the Knights Landing Ridge Cut; (2) a new channel across the Yolo Bypass from Knights Landing Ridge Cut to the Tule Canal; (3) an enlarged Tule Canal; and {k) a check structvire near the downstream end of the enlarged Tule Canal. Plate 6, "Profile, Plan and Typical Sections of Yolo Bypass Project/' shows these facilities. Check Structure (No. l) A check structure of reinforced concrete would be bixilt at the ridge cut entrajice to the new channel. Incorporated into the design of this check structure wovild be a transition section between the Knights Landing Ridge Cut and the new channel across the bypsiss. The structure would be divided into bays for stop logs. These features woiald control the discharge within permissable velocities, and would maintain the water surface elevations required for irrigation. The check structure would not infringe upon the existing capacity of the ridge cut for the discharge of winter flood flows. New Channel The new 10,000 foot long channel across the Yolo Bypass woxild extend from the mouth of the Knights Landing Ridge Cut to the Tule Cajial. -93- It woxild be imlined and wovild have side slopes of 3 to 1, an average depth of 10 feet, and a bottom width of 70 feet. The bottom of the new channel would slope from an elevation of U feet at the west end to 7 feet at the east end (USGS datum). The design capacity of the new chsuanel would be 2,000 second-feet. Channel construction would require the acquisition of an estimated 60 acres of land. This acreage would be sufficient to provide for the channel as well &s for alternative methods for disposal of an estimated 1+31,000 cubic yards of excavated material. The actual method of disposal should be determined prior to project construction. Some of this material might prove to be soil of a quality satisfactory for farming purposes; the jjossibility exists that such soil might be spread out so that the disposal area could be farmed. In the event of actual construction, the State Reclamation Board would have to approve the depth and configuration of proxxjsed si)oil areas. Enlarged Tule Canal The Tule Canal is situated adjacent to the east levee of the Yolo Bypass and is utilized for both irrigation and drainage. The enlarged Tule Canal would carry flows from the proposed new channel to the upper end of the toe drain of the Sacramento Deep Water Ship Chajinel. For prac- tical purposes, the capacity of the toe drain at this point, 2,1+00 second- feet, governs the hydraulic design of the Yolo Bypass Project. Therefore, the 2,1+00 second-foot capacity of the enlarged Tule Canal at the point where it enters the toe drain would be 1+00 second-feet greater than the cap6u:ity of the new channel across the Yolo Bypass. This greater down- stream capacity provides for drainage water to enter the Tule CaJial from lands farmed in the Yolo Bypass. Existing rights-of-way held by the .91.- r View of Tule Canal looking southward showing restricted channel capacity above High- way 40 crossing. Sacramento Deep Water Ship Channel and toe drain can be seen in background. View of the Tule Canal looking northward showing Sacramento Bypais entering Yolo Bypass from the right side of photograph, and the much restricted channel of the Tule Canal. Sacramento and San Joaquin Drainage District should be sufficient for the work required along the Tule Canal. These rights-of-way are under the jurisdiction of the State Reclamation Board. Tule Canal would be enlarged by excavating 225,^00 cubic yards from 3,800 lineal feet of a narrow section of the canal between the Sacramento Bypass and Highway kO. Some brush and trees would have to be removed. The enlarged canal would have side slopes of 3 to 1, emd a bottom width of 70 feet. The elevation (USGS datum) of the bottom of the canal would be at sea level at the intersection of the Sacramento Bypass and 1 foot below sea level at the intersection of the Southern Pacific Railroad bridge. In addition to the required excavation, small levees will be required at several locations to maintain the design water surfew:e in the Tule Canal from its junction with the new channel to the toe drain of the ship cheuinel. Plate 6 shows the locations of these levees. The required levees will total 15,300 lineal feet in length. Their construction along the Tule Canal will require 30,500 cubic yards of erabanlaaent material. The meiximum height of these levees including 1 foot of freeboeird, would be 4.5 feet. It was assximed that their side slopes would be 3 to 1 and that their crown width would be 12 feet. That portion of the levee across the mouth of the Sacreunento Bypass would have a maximum height of 2 feet. To mini- mize the obstruction to flood flows entering the Yolo Sypass frcan the Sacramento bypass, the freeboard at this point woiiLd be reduced to one -half foot. This is the freeboard provided by the west levee of the toe drain of the Sacramento Deep Water Ship Channel. The enlargement of the Tule Cemal and the construction of the low levees would require relocation of certain existing drainage facilities -97- in this area of ti..e Yolo B>-pas3. At some points, the new levees woiiLd interfere with existing irrigation ptunping facilities and these facilities also would require relocation. The preliminary designs made for these relocations would be subject to review during final design staLges should this project be constructed. Check Structure (No. 2) A check structure similar to that proposed for the downstream end of the Knights Landing Ridge Cut would be built neeir an existing check stjructure located about i4-,000 feet north of Highway kO. The proposed check structure would maintain water elevations at present levels in the Tule Canal during the irrigation season. Estimated Costs Based upon construction prices prevailing in I961, the estimated total capital cost of the Yolo Bypsiss Project would be $586,000. Levee construction emd canal excavation, including the removal of brush and trees, comprises $317>CKX) of the cost. The acquisition of rights-of-way and relocation of existing structures comprises the remaining $269,000. The amount estimated for rights-of-way woiald be subject to minor change depending upon the method vised to dispose of the material excavated from the new channel across the Yolo Bypass. The total amnual cost of the project worild be $1+1,200, with financing at an interest rate of four percent a yesir. A sumnary of capital euid annual costs of the Yolo Qypass Project is presented in Table 17. -98- TA.BLE 17 ESTIMATED CAPITAL AND AOTIUAL COSTS OF YOLO BYPASS PROJECT (In dollars) Item .' Costs CAPITAL COSTS Construction Items Embankment $ l6,300 Excavation New channel 129,500 Enlarged Tule Canal 90,200 Lands and damages Rights-of-way 15,000 Acquisition costs (30^) '<-,500 Relocations Check structures lUl,000 Irrigation and drainage structures 37>5QQ Subtotal $436,000 Contingencies (20^) 87,000 Engineering and administration (10^) 52,000 Interest during construction (U^) 11,000 Total Capital Costs $586,000 AWNUAL COSTS Interest (iv^) 23,^400 Repayment 3,800 Operation sjid maintenance 1^,000 Total Annual Costs ■ $ 4l,200 -99- Project Benefits Facilities of the Yolo Bypass would function primarily during the spring emd summer growing season when there would be no flood waters in the Yolo Bypass and when high stages in the Sacramento River would prevent the Colusa Basin Dirainage Cemal from discharging through the Knights Landing outfall gates. The Yolo Bypass Project would not relieve flood or drainage problems in the Colusa Basin at times when the Yolo Bypass would be flooded heavily by water diverted from the Sacramento River. Table l8 shows the reductions in frequency and dxiration of flooding which might be expected in Reach 2 under project conditions. At present, on the average, a flood affecting 3,000 acres will last l8 days and occur in seven out of ten years. Under project conditions, a flood affecting 3,000 acres will last, on the average, only 11 days and occur in about five out of ten years. This is a reduction of 22 percent in the frequency of floods of the size affecting 3^000 acres and a reduction of seven days in the period of inundation. Similar reductions will be reaJLized for floods of other sizes. The facilities of the Yolo Bypass Project also would reduce the extent of the area flooded; floods under project conditions would affect less land than floods of the same magnitude under pre-project conditions. Figures 11 and 12 show the probability of various sizes of floods in Reaches 1 and 2 and the area which would be flooded under conditions with and without the project. For Reach 1, Fig\ire 11 depicts only those con- ditions existing during the period April 1 through September 30. Flood conditions in the Yolo Bypass dviring the winter periods were not consid- ered because the bypass lands are established to convey winter flood waters. In Reach 2, adjacent to the Colusa Basin Drainage Canal, up to -100- o o •"-5 o o -P Cm O ■P •H O •^■H i) U CO u tJ o 0) -d o o ON LA LfN Lf^ CO CO LTv Lr\ Lf\ 00 OJ OJ ON VO on fd CO CY1 CVJ OJ OJ H Lf\ 8\n OD on o -* cK 00 CO f- >3) 8 LA OJ ■101- 100 z UJ UJ o o 80 UJ lu O O 60 Z E < m o 40 20 n"" ■■■■■■' ^ 1 -WITH PROJECT 10 15 20 FLOODED AREA IN 1000 ACRES 25 30 Figure II. PROBABILITY OF FLOODING (April I Through September 30) IN REACH I, THE NORTHERN YOLO BYPASS, WITH AND WITHOUT YOLO BYPASS PROJECT 100 80 3 60 z < 40 S 20 ID O X a. / WITH 3UT PROJE CT /—WITH PROJECT \ \ V ^-^^ 10 15 20 FLOODED AREA IN 1000 ACRES 25 30 Figure 12. PROBABILITY OF FLOODING IN REACH 2, KNIGHTS LANDING TO COLLEGE CITY, WITH AND WITHOUT YOLO BYPASS PROJECT 500 acres of land presently kept idle in the spring ajid summer by the threat of floods could be brought into production under project conditions. Although a greater degree of flood relief could be achieved by increasing the capacity of the Yolo bypass Project drainage facilities, the controlled discharge from the project was limited to the capacity of the ship channel toe drain to avoid any increase in downstream flood damages. The Yolo Bypass Project would provide benefits to Reaches 1 and 2 by preventing flood damages. Flood damages for conditions at present and for conditions which would exist after construction of the project, as well as the resiiltlng benefits, were computed by the method used to compute such damages and benefits for the Colusa Basin Levee Projects. Average crop damages, based on prices prevailing from 1952 to 195^, corresiwnd to those which occur from flooding diaring the period from April 1 through September 30. Total flood damages were computed for several sizes of floods and analyzed to determine frequency of occurrence. The probability of flood damage with and without the Yolo Bypass Project is shown on Figure 13. The average smnua], crop damage reduction benefit for Reaj^hes 1 and 2 is $2it-,000 and $23,800, respectively. The average annual miscellaneous damage reduction benefit in the same reaches is $1,U00 and $6,000, respec- tively. The total average einnual flood damage reduction benefit which may be credited to the Yolo Bypass Project, therefore, is $55,200. Economic Justification The Yolo ByiJass Project has an average ajumal cost of $^1,200, an average annual flood damage reduction benefit of $55,200. The benefit-cost ratio of 1.3^ to 1 shows the project to he economically justified. -103- 30 40 50 60 70 PROBABILITY OF ANNUAL OCCURRENCE IN PERCENT Figure 13. PROBABILITY OF FLOOD DAMAGE WITH AND WITHOUT YOLO BYPASS PROJECT Although the capital cost ol' the project, estimated to be $^66,000, is relatively low, project benefits accrue to a relatively small area within the Colusa Basin and to only a small number of land owners. No analysis was made of a possible method for financing, constructing, and operating this project, nor was an analysis made of the ability of the beneficiaries to pay for the project. ■105- CHAPTER V. CONCLUSIONS AND RECOMiffiN DAT IONS Principally an agricultural area, the Colusa Basin is also of great value as a habitat for wildlife and an area for recreation. The natural advantages of this area are flat topography, long hot summers, and a good water supply. From the standpoint of both texture and alkalinity, the poor quality of the soil in much of the area has restricted crop pro- duction largely to rice and irrigated pasture. Agricultural development began at an early date and has continued in conjunction with the reclamation of lands from frequent and widespread flooding from the Sacramento River, Reclamation works protect the basin against flooding from the Sacramento River, but although these works have provided a high degree of protection to certain lands, they have not controlled floods from runoff of western tributary streams or from irrigation return water. As a result of field investigation and the analysis of available data on flood control and drainage problems in the Colusa Basin, the following conclusions and recommendations are made: Conclusions 1. Because flooding from the Sacramento River has been largely controlled by a system of river levees, bypass channels and upstream reservoirs, little damage results from this source, 2, Floods from tributary runoff and precipitation within the basin cause frequent and widespread flooding, restricted mostly to the winter months of October through March. Because the frequency with which this area is flooded has limited development in the flood plain, mainly to agriculture and waterfowl hunting facilities, only moderate amounts of damage occur. The farm lands are seldom planted in the winter. The area contains almost no domestic development and few paved roads or public utilities, -107- 3. Serious flood problems in the Colusa Basin arise from spring flood flows that are created principsdly, and at t.imes wholly, by irrigation return flows. The Colusa Basin Drainage Canal is inadequate to carry the spring flood flows when high water stages in the Sacramento River prevent discharge through the Knights Landing outfall gates. 4. Although water quality problems exist in some local areas as a result, mainly, of the leaching of alkali Isinds, the quality of available water supplies in general and of the water in the main dradnage channel in particular was found to be satisfactory. 5. Recreation in the Colusa Basin, in the form of hunting for pheasants and migratory waterfowl, constitutes one of the principal resources. A reduction in flooding in the basin could increase slightly the hunting oppoirtunities, but land use changes made possible by flood prevention might seriously reduce the area suitable for migratory waterfowl, 6. The February 1958 flood in the Colusa Basin was the largest recent flood for which records are available. In that month, a maximum daily flow of 23,900 second-feet was recorded in the flood channel of the Colusa Basin Drainage Caned, at the Highway 20 Bridge. 7. Future flood and drainage problems in the Colusa Basin may be modified by possible developments as follows: a. Future water developments in the Sacramento River Basin will not significantly relieve winter floods in the Colusa Basin, but may cause summer or fall drainage floods not presently experienced. It is assumed that any flood conditions induced in this manner would be alleviated by those responsible. b. Flood flows from streams tributary to the Colusa Basin Drainage Canal are expected to be little changed in the future unless the carrying capacities of the tributary channels are increased. Such increased capacities could increase flood peaks in the drainage canal. -108- ^ c. Predicted land use changes will result in somewhat ■ larger irrigation return flows throughout the summer months, but no significant increase in magnitude or change in frequency of damaging spring drainage flows is expected to occur. 8. Flood characteristics used herein for the design and analysis of flood control and drainage projects were assumed to remain essentially the same throughout the future fifty year period as experienced in the past. Frequency studies indicate that a flood with a probability of occurrence of two percent (one expected to be equalled or exceeded once in 50 years on the average) would have a peak discharge of approximately 25,000 second-feet in the Colusa Basin Drainage Canal at the Highway 20 Bridge near Colusa. 9. On the basis of the frequency of occurrence of floods, the future crop pattern estimated to prevail without additional flood protection, and those farm costs and prices which prevailed from 1952 through 1956, it was estimated that crop flood damages in the Colusa Basin woiild average $150,000 a year. 10. It was similarly estimated that without additional flood protection, miscellaneous flood damages to private property and public facilities would average $46,000 a year. 11. Engineering works for solution of flood and drainage problems were designed to operate without interference to water rights and diversion of water for irrigation uses. 12. The Colusa Basin Levee Projects were evaluated to detennine the degree of protection afforded by each of three sizes of levee projects designed. These projects would protect lands in the Colusa Basin between Knights Landing and Willows from flooding from the Colusa Basin Drainage Canal and Willow Creek, The Two Percent Project, (once in 50 year flood protection) with a capital cost of $26,033,000 and an annual cost of $1,771,000 would -109- provide annual benefits of $578,000. The Five Percent Project, (once in 20 year flood protection) with a capital cost of $23,322,000 and an annual cost of $1,549,000, would provide annual benefits of $550,000. The Ten Percent Project, (once in 10 year flood protection) with a capital cost of $20,126,000 and an annual cost of $1,365,000, would provide annual benefits of $5A4,000. In the case of each project, costs would exceed benefits, and therefore not one of the levee projects was found to be economically justified for the present or expected future level of development in the Colusa Basin. 13. A study of the wildlife aspects of the Colusa Basin Investigation was not required under the authorizing legislation. However, until this aspect of the problem has been fully investigated, the proper approach to the solution of the problem cannot be ascertained with a high degree of confidence. This is particularly true with respect to possible state or federal participa- tion in a project, for the wildlife aspects are of great interest and importance to the public at large and would necessarily influence any decision reached within the framework of public interest. Even from a local point of view, maintenance of existing wildlife areas may be more beneficial in overall economic terms than alleviation of the local flooding problem. 14. The Foothill Reservoir Project, comprising flood control reservoirs on 17 tributary streams in the western foothills, was determined to be a less desirable solution to flood and drainage problems in the Colusa Basin than that provided by any of the Colusa Basin Levee Projects. The capital cost of the Foothill Reservoir Project would be $28,760,000. Because this cost would exceed that of any of the levee projects, and because the accomplish- ments and benefits of the project would be less than those of any of the levee projects, the project would not be economically justified. -110- 15. Watershed management, coupled vith some levee works in the valley area, might provide an inexpensive vay to reduce flood hazard. The reduction in flood hazard resulting from watershed management was not evaliiated due to the lack of data applicable to the foothill area. 16. The Yolo Bypass Project would increase the outlet capacity of the Knights Landing Ridge Cut into the Yolo Bypass and improve drainage in the area. It woxold function primarily to alleviate damages resulting from irrigation return flows. The project woiiLd protect lands in the lower Colusa Basin between Knights Landing and College City and in the northern Yolo Bypass between the Sacramento Deep Water Ship Channel and the mouth of the Knights Landing Ridge Cut. Two check stmctvires wovild maintain summer water levels at the elevations required for punrped diversions. The Yolo Bypass Project, with a capital cost of $586,000 and an annual cost of $41,200, would provide annual benefits of $55,200. The benefit-cost ratio -- 1.34 to 1 — indicates economic justification. Recommendations It is recommended that: 1. Although an improved drainage channel and levee system essentially as described herein conrprises the most desirable engineering solution to existing emd foreseeable flood problems, it not be adopted for construction at this time by local, state, or federal interests because the costs greatly exceed the benefits. 2. The economic justification of an improved drainage channel and levee system be re-eval\iated in the future when improved land use and the threat of excessive damage thereto creates a greater demand for flood protection. -Ill- 3. Future reclamation and flood protection provided by local interests to limited areas within tue Colusa Basin be made compatible with an eventual basin-wide plan such as the IVo Percent Levee Project. k. The chajinels of tributary streams entering the Colusa Basin Drain- age Canal from the west be maintained essentially in their present condition. 5. Future analysis of flood control emd drainage systems in the Colusa Basin include recreation and wildlife data sufficient in detail and scope to allow evaluation of these resources to be included in determinations of economic justification and financial feasibility. 6. The Yolo Bypass Project as described herein and shown to be economi- cally justified to be adopted by an appropriate local districts or public agency for constnaction to alleviate flooding along the southern reach of the Colusa Basin Drainage Canal and in the northern Yolo Bypass. ■112- PLATE I ^ IL /-^ LEGEND HISTORICALLY FLOODED AREA — POSSIBLE LEVEE AND DRAINAGE PROJECTS POSSIBLE FOOTHILL RESERVOIR PROJECT STATE OF CALIFORNIA THE RESOURCES AGENCY OF CALIFORNIA DEPARTMENT OF WATER RESOURCES NORTHERN BRANCH COLUSA BASIN INVESTIGATION EXISTING AND POSSIBLE FLOOD CONTROL AND DRAINAGE FEATURES SCALE OF MILES 2 LEGEND I^^V HISTORICALLY FLOODED AREA — POSSIBLE LEVEE AND DRAINAGE PROJECTS 4^^^^ POSSIBLE FOOTHILL RESERVOIR PROJECT STATE OF CALIFORNIA THE RESOURCES AGENCY OF CALIFORNIA DEPARTMENT OF WATER RESOURCES NORTHERN BRANCH COLUSA BASIN INVESTIGATION EXISTING AND POSSIBLE FLOOD CONTROL AND DRAINAGE FEATURES PLATE 2 LEGEND PRESENTLY IRRIGATED LANDS IRRIGABLE VALLEY LANDS ~\ IRRIGABLE HLLL LANDS STATE OF CALIFORNIA THE RESOURCES AGENCY OF CALIFORNIA DEPARTMENT OF WATER RESOURCES NORTHERN BRANCH COLUSA BASIN INVESTIGATION IRRIGATED AND IRRIGABLE LANDS 1954-56 SCALE OF MICES 2 2 * NTQ i^? ;ramento, ss-~- .^1 ro ^*^ .^.s, .'/^^ ?!" S^ ^S«J«e^ etf> OREGON STATE OF CALIFORNIA THE RESOURCES AGENCY OF CALIFORNIA DEPARTMENT OF WATER RESOURCES NORTHERN BRANCH COLUSA BASIN INVESTIGATION PRINCIPAL IRRIGATION WATER SERVICE AGENCIES AND PROPOSED WATER SERVICE AREAS SCALE OF MILES 2 PLATE 4 J.^^ ro ^o^ xB v*^ '^s" 7<^ c :^- '~7 / ^ ^SweeneVA m STATE OF CALIFORNIA THE RESOURCES AGENCY OF CALIFORNIA DEPARTMENT OF WATER RESOURCES NORTHERN BRANCH COLUSA BASIN INVESTIGATION RECLAMATION AND LEVEE DISTRICTS 1 SCALE OF MilFS STATE OF CALIFORNIA THE RESOURCES AGENCY OF CALIFORNIA DEPARTMENT OF WATER RESOURCES NORTHERN BRANCH COLUSA BASIN INVESTIGATION RECLAMATION AND LEVEE DISTRICTS SCflL£ Of MiLfS EXISTING LEVEE • STING CHANNEL MAX. W.S- PLATE 5 TING CHANNEL EXISTING LEVEE EXISTING IRRIGATION DITCH 'PICAL SECTION OF NAGE PUMPING PLANT BREAKER DISCHARGE W S. PROPELLER TYPE PUMP ] STATE OF CALIFORNIA THE RESOURCES AGENCY OF CALIFORNIA DEPARTMENT OF WATER RESOURCES NORTHERN BRANCH COLUSA BASIN INVESTIGATION PROFILE AND TYPICAL SECTIONS OF COLUSA BASIN LEVEE PROJECTS 1962 - PBOJECT LtVtt - "IS'^cT KW -..,.„.....-j ■ ^^ -ri^ "" *'7 ^ ^ iGOO'OO 7400>00 iSOO'OO £000(00 >SOO<00 IGOOtOO laOO'OO 1200*00 STATIONING IN CEET PROFILE OF WILLOW CREEK AND COLUSA BASIN DRAINAGE CANAL THE RESOURCES AGENCY OF CALIPORNIA DEPARTMENT OF WATER RESOURCES NORTHERN BRANCH COLUSA BASIN INVESTIGATION PROFILE AND TYPICAL SECTIONS OF COLUSA BASIN LEVEE PROJECTS 1962 NATURAL GROU^O STATION 620+00 STATION 444+00 STATION 300+00 --CHANNEL EXCAVATION ^NATURAL GROUND STATION 165 + 00 PROJECT LEVEE NATURAL GROUND STATION 85*00 AL SECTIONS -LOOKING UPSTRFAM SCALE I ■ 20 PLATE 6 STATE OF CALIFORNIA THE RESOURCES AGENCY OF CALIFORNIA DEPARTMENT OF WATER RESOURCES NORTHERN BRANCH COLUSA BASIN INVESTIGATION PROFILE, PLAN, AND TYPICAL SECTIONS OF YOLO BYPASS PROJECT 1962 PLATE 6 NATURAL GROUTO STATION 620+00 STATION 444+00 STATION 300+00 STATION 165 + 00 PROJECT LEVEE NATURAL GROUND STATION 85*00 AL SECTIONS -LOOKING UPSTRFAM SCALE r> 20' STATE OF CALIFORNIA THE RESOURCES AGENCY OF CALIFORNIA DEPARTMENT OF WATER RESOURCES NORTHERN BRANCH COLUSA BASIN INVESTIGATION PROFILE, PLAN, AND TYPICAL SECTIONS OF YOLO BYPASS PROJECT 1962 ^•MTURAL GROUHO STATION 620*00 STATION 444*00 STATION 300*00 «e0*OO 600KI0 9 S 0*00 400+00 J50*O0 soo*oo STATIONING IN FEET PROFILE OF YOLO BYPASS PROJECT ALONG THE WEST LEVEE OF TULE CANAL -^ ^CHiNMEl STATION I6J*00 ST*TE OF CALIFORNIA THE RESOURCES AGENCY OF CALIFORNIA DEPARTMENT OF WATER RESOURCES NORTHERN BRANCH COLUSA BfiSIN INVESTIGATION PROFILE, PLAN, AND TYPICAL SECTIONS OF YOLO BYPASS PROJECT !962 h^ THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW *■_ RENEWED BOOKS ARE SUBJECT TO IMMEDIATE RECALL , m§ APR 4 1978 ipfi ? V%t, - RECEIVED PHYC SCI library: LIBRARY. UNIVERSITY OF CALIFORNIA, DAVIS Book SUp-50m-12,'64(F77284)458 354266 California. Dept, of Water Resources, Bulletin, PHYSICAL SCIENCES LiB(W?Y _„ - -- illriliilill I 75 00641 5361