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Pajaro River Watershed Study

The Pajaro River Watershed Flood Prevention Authority (Authority) has completed Phase 3 of the four phase Pajaro River Watershed Study. The Phase 3 Report outlines, summarizes, and explains the progress achieved to date within the Pajaro River Watershed Study.

Phase 1 consisted of modeling both the hydrologic and sediment regimes of the watershed. The results of Phase 1 provided a better understanding of the characteristics of the watershed and changes over time that affect flooding frequency and flooding potential in the downstream reaches of the Pajaro River.

Phase 2 identified project alternatives that would provide flood protection for the Pajaro River from Chittenden to Monterey Bay from the 100-year flood flows identified in Phase 1. The Phase 2 Study projects were developed to coordinate with a concurrent Army Corps of Engineers (Corps) Lower Pajaro River flood protection project.

After the conclusion of Phase 2, the Corps identified a 100-year flood protection project for the Lower Pajaro County BoundariesRiver without any upstream projects.

The Corps 100-year flood protection project is based on the assumption that the watershed conditions (or current level of flood attenuation provided in the upper watershed) are maintained. The Phase 1 model results highlighted the natural flood attenuation benefits of Soap Lake and the critical importance of maintaining those benefits as part of any Pajaro River flood protection solution.

The focus of the Authority work shifted to ensure that the flows passing through the Lower Pajaro River Project would not increase above the currently predicted levels. The most direct way to achieve this goal was to preserve Soap Lake and its attenuation capabilities.

Phase 3 and 4a defines and documents the preferred method to maintain the Soap Lake attenuation and storage capacity, known as the Soap Lake Floodplain Preservation Project. In Phase 3 Soap Lake was hydraulically modeled and the floodplain boundaries defined. The impacts of flooding and land use preservation were examined in compliance with the California Environmental Quality Act (CEQA) and the cost of the Project estimated.


Pajaro River Watershed Study
Phase 1:

Stream Flow Modeling

Phase 2:
Development of Flood Protection Alternatives

Phase 3:
Selection of Projects and CEQA Analysis

Phase 4:
Flood Protection Implementation

Phase 4 of the Study included the following four tasks that contribute to
or support flood protection for the Pajaro River Watershed:

 • Develop the Soap Lake Floodplain Preservation Project Implementation Plan;

 • Create three sediment models;

 • Improve flood forecasting capabilities; and

 • Perform a fisheries study of San Felipe Lake.


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