Agenda Item 9 Sutter Bypass

CVFPB Meeting

April 17, 2009

BACKGROUND

Local citizens and levee maintaining agencies in the vicinity of the Sutter Bypass have expressed concerns that vegetation in the Sutter National Wildlife Refuge may obstruct Bypass flows and could have negative impacts on the carrying capacity of the Bypass.

1

BACKGROUND

The Board conducted a site visit of the Bypass as part of its September 2008 meeting and passed resolution 08-19 in December 2008 directing its staff to take steps to address local citizens and levee maintaining agencies concerns.

1

BACKGROUND

Board members and local interests have further expressed that they want to be more precise and to ask the staff to specifically study the impacts of the Refuge on the carrying capacity of the Bypass.

1

PROGRESS AS OF TODY

Design flows: Based on the discussion among DWR, USACE and the Board it has been decided that the 1957 profile and flows will be used to assess the impacts of the vegetation on the carrying capacity of Sutter Bypass.

3

Hydraulic Analysis (modeling efforts)

• DWR has a one-dimensional steady flow hydraulic model developed using the Corps’ HEC-RAS modeling software

• DWR has completed its modeling runs and can brief the Board during the May or June Board meeting

• DWR staff can separate the reach covering the Sutter National Wildlife Refuge to show its impacts on the carrying capacity of the Bypass

• Board has hired hydraulic engineer who can independently review the DWR analysis and can provide its assessment to the Board

• Results of the hydraulic analysis will help DWR to update its maintenance plan identifying area where vegetation needs to be cleared

4

• If the modeling results conclude that the vegetation growth in Refuge is not allowing the design flows to pass without encroaching on the freeboard that conclusion would provide the needed documentation to begin negotiations with the U.S. Fish and Wildlife Service for removing vegetation

• Board staff will continue its coordination and efforts with DWR, Corps and NWS to assess the need of a two dimensional model to ascertain the impacts of the vegetation and structures on the carrying capacity of the Sutter Bypass.

NEXT STEPS

5

Staff recommends that the Board approve Resolution No. 2009-11 directing its staff to coordinate with DWR, the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service to assess the effect of the Sutter National Wildlife Refuge on the carrying capacity of the Sutter Bypass.

STAFF RECOMMENDATION

6