Pájaro River Watershed Flood Protection Plan - The Pajaro River ...

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Executive Summary Because of the unique geologic and hydrologic setting of the Pájaro River in its dynamic watershed, traditional approaches to flood control may not be effective and will require constant expensive maintenance. The river that now flows through it did not create the lower Pájaro Valley and it is not possible to “restore” such a system to stability because there is no evidence of any past stable Pájaro River channel in the lower valley. An artificial flood control channel was constructed by early residents and was upgraded by the U.S. Army, and later by the Corps’ of Engineers to try to minimize property losses associated with large floods in this watershed of about 1300 square miles. Historically the Pájaro watershed system has carried runoff from Santa Clara, San Benito, Santa Cruz, and Monterey counties into Monterey Bay through various channels in Monterey County. The river is now artificially confined to join Corralitos Creek to enter the ocean along the Santa Cruz/Monterey County border. We find that a substantial area of on-channel storage of floodwater has been lost in the upper watershed areas of San Benito and Santa Clara counties. Some of this lost storage can be recovered for little or no public cost to reduce flood heights (on the order of 4 feet) in the artificial floodway channel of the lower river. Redesign of that lower channel may accommodate added flood capacity to provide a working flood channel that carries a generously estimated 100-year flood volume. Such redesign, coupled with upstream channel restoration that is part of a flood storage enhancement project, will have very substantial wildlife and water quality habitat benefits. DRAFT 7/22/03 2 Pájaro Watershed Flood Management
Table of Contents Executive Summary Table of Contents Chapter 1 Introductory Context The Pájaro Watershed System Dynamics The Watershed Lower Watershed – Santa Cruz and Monterey Counties Upper Watershed – San Benito and Santa Clara Counties The River System Stable Channel Alternatives This Project Report Coordination with other Raines, Melton, Carella Philip William Associates U. S. Army, Corps of Engineers i ii Chapter 2 Design Flood Analyses Purpose Methods Data Collection Data Analysis Results Regional Analyses Discussion Storm Patterns and History Chapter 3 Upper Basin In-channel Flood Storage and Restoration Opportunities Basic Conclusions Theory Methods Findings Channel Incision Channel Diversions Restoration of Channel Functions Suggested Restoration Options for the San Benito River Aggregate Mining Company Opportunities Suggested Enhancement Options for the Upper Pájaro River Conclusions References Cited and Historical Materials Consulted DRAFT 7/22/03 3 Pájaro Watershed Flood Management
Page 1: California State University Robert
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Page 7 and 8: that today bears the name Pájaro.
Page 9 and 10: Map B. 1908 Parcel Map of a portion
Page 11 and 12: Map A 1875 based on 1854 land surve
Page 13 and 14: Upper Watershed, San Benito and San
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Page 19 and 20: The current project attempts to rec
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Page 23 and 24: where: g adj is the adjusted skew g
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Page 27 and 28: value for the maximum possible 100-
Page 29 and 30: Regional Analysis The trend in perc
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Page 35 and 36: We also find that on the order of 6
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Page 49 and 50: APPENDICES & Figures APPENDIX 1: No
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APPENDIX 2: 1995 and 1998 Storm Com
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50 Corralitos Creek Hydrograph & Co
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Figure 16 - San Benito River channe
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Fig 15 Stream Barb Structures DRAFT
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Corps’ Data presented Alternative
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California State University Robert
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. illustrations, on an interim repo
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APPENDIX 3 Streambank Property Owne
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Historical Change in San Benito Riv
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