「[[ L st SU 85. Extent of local cooperation required. It is essential to proper maintenance of the project and satisfactory working agreements ef between the United States and local interests that suitable impro ment districts or other legal authorities be formed to include all the areas to be protected in Pajaro Valley and the vicinity of Gilratsid Before any construction is started, local interests should provide, wies of /out cost to the United States, all lands and easements required for the project, and give assurances satisfactory to the Secretary of War that jard they will maintain and operate the levee systems under regulations aus to be prescribed by him, and hold and save the United States fre ajar from damages from the construction and operation of the projet works. fonte pe E). Cours & 17 86. Local interests should also agree to make, at their own expense, i preadi DISCUSSION 925, al Bosts an 87. Flood conditions.--The flood problems in various parts of the drainage basin are outlined at length in paragraphs 54 to 63, inclusi. The principal flood problems are here recapitulated with some discussion of related problems in the several areas. nited ate, for dered 88. In the Carnadero-Llagas Creek and San Felipe Lake regn, overbank flow follows low swales and depressions between the normal 91, P stream channels, merging into a large flood plain extending from the xtensiv vicinity of Gilroy to San Felipe Lake and Sargent. Along the upper either reaches of the streams tributary to the upper Pajaro River, especiaffect fo vas inv he oby etties, o most mple in the irrigated lands of South Santa Clara Valley, water conservationecessity 92. Po flood control in this area could be accomplished. In the lover The part Complete problem in the flood plain areas. In this area, however, extension and enla The estim an econo magn percent benefits e plan of improvement for flood control for which the prospective benefits would be commensurate with the costs. 89. In the San Benito River-Tres Pinos Creek region, bank erosion constitutes the principal flood damage. There is little inundation outside the natural stream beds. These streams carry great quantities of sand and silt which are deposited in the Pajaro River. During the summer months, the presence of San Benito River sand in the Pajaro River is regarded as beneficial by local interests in that it causes delay in the depletion of ground water supplies along the upper Pajaro River. In the winter, the prolonged discharge from the San Felipe Lake area carries much of this sand out of the river into Monterey Bay. 90. In South Santa Clara Valley around Hollister, and also in San Benito Valley around San Juan Bautista, local interests desire reservoirs above all other means of flood control. Investigations have demonstrated that only one site exists at which an effective flood-control reservoir could be constructed. This is just below the confluence of Tres Pinos and Bird Creeks with the San Benito River. Construc-tion of an adequate flood control reservoir at this site, which is not favorable geologically, would cost more than $3,000,000, of which only $1,400,000 is justified by the prospective flood control benefits. To secure water conservation benefits, it would be necessary to build a larger and more expensive dual-purpose reservoir in which water conservation interests would have to pay the large flood-control deficit of more than $1,600,000 in addition to the other development costs. Local interests have failed to agree on either of two reservoir and spreading schemes developed by the Hollister irrigation district since 1925, and there is evident disagreement regarding the distribution of costs and benefits proposed in these previous schemes, one of which was investigated in considerable detail. In view of this situation and the obvious lack of advantage to local interests in joining with the United States in the construction of a dual-purpose reservoir at this site, formulation of a detailed plan for such a reservoir is not considered warranted at this time. 91. Pajaro River, existing levee improvement.-Overbank flow is extensive in Pajaro Valley and causes most of the flood damage. Neither tides nor sand bar formations at the river mouth materially affect flood flows in this reach of the river. Consequently, there is no necessity for attempting to maintain an open river mouth by means of jetties, or otherwise, for the purpose of flood protection. Irrigation is almost universally practiced here, but ground water supplies are ample and appear to suffer only minor depletion during dry cycles. The partial flood protection afforded by the existing levee system in the Watsonville area provides average annual benefits estimated at $28,600. The estimated annual cost of these levees is $14,870 giving an economic ratio for the existing work of 1.92 to 1.0. 92. Pajaro Valley levee project A.-It is estimated that the proposed extensions of the existing levee system in this plan would effect nearly complete protection of most of Pajaro Valley against all floods up to the magnitude of the 1-percent-chance flood in the urban areas and the 2-percent-chance flood elsewhere. The additional average annual benefits expected to accrue under this plan are estimated at $40,600. The estimated annual cost of the proposed additions and extensions is $35,000, giving an economic ratio of 1.16 to 1.0 for the added benetts such and added costs of this project. The degree of flood protection whihvation would be provided by the complete levee system may be expressed as praise about 85 percent of total protection of the entire Pajaro Valley from 96. floods of all magnitudes. local 93. Pajaro Valley levee project B.-The alternate plan of improcal inte ment in this area would comprise only that portion of the recor. 42 an mended project which would strengthen the existing levees and the re adequately tie them to suitable points to provide positive flood peons of in tection against all floods up to the magnitude of the 1-percent-charence the flood. This plan would effect additional average annual benefis on o estimated at $17,100 at an added annual cost estimated at $13,6, fonterey giving an economic ratio of 1.25 to 1. The degree of flood protectin atsonvi which would be provided by the modified levee system may be posed expressed as about 55 percent of total protection of the entire Pajoral co Valley from floods of all magnitudes. The plan contains a veycal inte undesirable floodway feature at the upstream and downstream velved terminals. $1.000 W aprovem 94. Carnadero Creek levee project.—The existing levee on Carnado Creek was designed to protect the town of Gilroy and was party 43.300 1 rebuilt in 1938 as a Works Progress Administration project. Itseek pro found that this levee is inadequately constructed to resist the larg 15.100 a floods. Strengthening and extending it somewhat would adequate sts are protect the town and some nearby agricultural areas from all floods fintely up to the magnitude of the 1-percent-chance flood, thereby providigestion additional average annual benefits estimated at $3,100. The esojects w mated added annual cost of the project is $2,570, giving an economic terests an ratio of 1.20 to 1.0 for the proposed new work. While this plan ver by would afford nearly complete flood protection for Gilroy and the the re agricultural lands between it and the levee, this protection woulades bo oma Priet amount to only about 25 percent of complete flood protection e represe be Carnadero Creek. However, flood damages are not found to sufficiently concentrated elsewhere on the creek or in South Sancts are of Clara Valley to justify the construction of extended flood-protectinted that work. the 95. Selection of the most practicable plans of improvement.--In v of the economic justification established above for the extension of existing levee system to protect most of Pajaro Valley and the fictjaro soil that the interests of the community as a whole would be served best tobability by the larger project, it is concluded that project A should be regarded ad assessm as the most practicable plan of improvement for flood control in Fatsonvill Pajaro Valley. This project would adequately meet the desires of local interests in Watsonville and vicinity and receive strong lea support. The selection of the Carnadero Creek levee for the prote tion of Gilroy as the most practicable plan of improvement for flod 97. The d stricts, ea operation amended (a) That control in South Santa Clara Valley is based entirely on economic studies. At this time no other flood control or multi-purpose cores of loc econor bination of irrigation and drainage project is found to be economicalymplete pro justified in the Pajaro Basin. However, in the future, if the needs not con irrigation or drainage become more pressing and construction (6) That reservoir storage or other work is undertaken primarily for sud control purposes, then the possibility may develop that some considerationservation should be given to flood control in connection with such construction. stined at Not printed. n such a case, flood control would be only incidental to water conervation or drainage and the possible benefits to be gained should be ppraised at that time. 96. Willingness and ability of local interests to meet the requirements f local cooperation.-In view of the favorable statements made by cal interests at the public hearing (see par. 46 and also appendix I,1 p. 42 and 44), it is believed that they are able and will agree to meet the requirements for cooperation set forth herein. No modificasions of improvements desired have been submitted by local interests ince the preliminary examination was held. However, informal disBE ussion of the proposed projects, with responsible local interests in Monterey, Santa Clara, and Santa Cruz Counties and in the towns of Watsonville and Gilroy, indicates that they will readily support the roposed plans of improvement for flood control, provided the nonfederal costs can be equitably allocated to the benefited communities. ocal interests, at the time of the public hearing, advanced plans that avolved the expenditure of $155,000 of local funds of which about 91,000 was primarily for flood control. In the proposed plans of mprovement, the project first-cost allocations to local interests are 243,300 for the Pajaro Valley project and $6,000 for the Carnadero reek project. Annual costs allocated to local interests amount to 15,100 and $280, respectively, for each project. These increased osts are recognized by local interests. However, local opinion is efinitely in favor of furnishing to the best of their ability such coperation as may be necessary to construct these two flood-control rojects when Federal funds are available after the war. Local aterests are well organized and are represented on the lower Pajaro liver by Monterey and Santa Cruz Counties, the city of Watsonville, nd the recently organized Pajaro soil conservation district, which acludes both banks of the river. The interests on Carnadero Creek re represented by Santa Clara County, the city of Gilroy, and the oma Prieta soil conservation district. Both soil conservation disricts are organized under California laws. No difficulties are anticiated that would defeat the forming of these two flood-control istricts, each with the necessary authority and ability to fulfill the ooperation requirements of section 3 of the Flood Control Act of 1936 s amended. A resolution was received from the directors of the Pajaro soil conservation district, indicating that there is a reasonable robability that local interests will organize an effective flood-control nd assessment district on the lower Pajaro River in the vicinity of Watsonville. A copy of this resolution is presented in appendix Ĭ.1 CONCLUSIONS 97. The district engineer finds: (a) That the construction of works which would meet all the lesires of local interests, as stated at the public hearing, and provide complete protection from floods in the Pajaro River and its tributaries s not economically justified by the prospective benefits at this time. (b) That construction of reservoirs in the basin primarily for lood control or as multipurpose projects in combination with water onservation, or with other works for drainage, is not economically ustified at this time. However, in the future, if construction is 1 Not printed. undertaken primarily for irrigation or drainage needs, the possibly may develop that incidental flood-control benefits could be gained through proper cooperation at that time. (c) That damages from excess water in the lowland area betwe Gilroy, Sargent, and San Felipe Lake are caused partly by pred drainage and that in some alkaline areas, these damages are ofset by substantial benefits from flooding. TOMOT (d) That the most practicable plan of improvement in Paro Valley would consist of reconstruction and extension of the exising levee system in the vicinity of Watsonville to provide nearly compete flood protection for the valley (designated plan A) at an estimated first cost of $741,000 and an annual cost of $35,000, and would atird additional flood control benefits evaluated at $40,600 annually. (e) That the most practicable plan of improvement in South Sta Clara Valley would consist of reconstruction and extension of the th existing levee in the vicinity of Gilroy at an estimated first cost of Calif $65,000 and a total annual cost of $2,570, and would afford additical to: Th flood-control benefits evaluated at $3,100 annually. 1. TI strib RECOMMENDATIONS in so Servo on of rospect 2. Th 98. The district engineer recommends that the existing levees the vicinities of Watsonville and Gilroy be reconstructed and extened by the United States at an estimated first cost of $741,000 for the Pajaro Valley levee (plan A), of which $497,700 would be made available from Federal funds and $243,300 is allocated to local interests; fin and at an estimated first cost of $65,000 for the Carnadero Creek leree near Gilroy, of which $59,000 would be made available from Federal funds and $6,000 is allocated to local interests; provided that, pror to construction, local interests in each of their respective areas: (a) Provide, without cost to the United States, the required laads and easements for construction and maintenance, estimated to ast $125,000 for the Pajaro Valley project and $4,000 for the Carnadro Creek project. cinity de mou jaro (b) Provide at their own expense on the Carnadero Creek project, flowage rights for flooding adjoining lands, estimated to cost $2,00 (c) Relocate, at their own expense, on the Pajaro Valley prot all existing improvements to lands in the levee right-of-way, estimated to cost $63,300. (g) Give assurances satisfactory to the Secretary of War that t will: Maintain and operate the project works in accordance with ould ddition cal int (d) Agree to accomplish, at their own expense, on the Pare Valley project all required modifications in the Thurwachter Brige and approaches, estimated to cost $9,000. ts affor stimate (e) Pay to the United States the sum of $46,000 as the estimated cost of paving special channel transition and other works required on the Pajaro Valley project to enlarge the inadequate clearance under the present Main Street Bridge at Watsonville, or, as an alternate. adequately increase the channel capacity at their own expense by means of suitable bridge modifications. (f) Establish satisfactory arrangements for cooperation with the United States and maintenance of the projects through city, county, or other suitable authorities. dur estim terests cal co $59.000 nual c ( 3. Th mprove Vision ervative Projects Fitutes & er is a |