So Simple, So Important: the Fremont Weir

Doesn't look like much but mightily important for flood protection

Doesn’t look like much but mightily important for flood protection

The Fremont Weir does not impress.  It is about 1.5 miles long (looking like this all along the way).  The Sacramento River is about 100 yards to the left of this photo.  On the day this was taken in March the River was bucolic and lazy.  Nothing suggested that it could swell to the point of overflowing and overtop the Fremont Weir. Yet, during a major storm event this unassuming weir diverts up to 80% of the Sacramento River flows thus protecting City of Sacramento, West Sacramento, and Davis from flooding.  The water flows into the Yolo Bypass.  The I-80 and I-5 causeways allow traffic to continue to move and the water can fill the 59,000 acre bypass to fill from levee to levee and sending it around the estuary to the Bay just above Rio Vista.

Several plans are taking a look at the bypass system and suggesting changes:

  • Central Valley Flood Protection Plan : the regional plan for Sacramento/North Delta is looking at changes to the Yolo Bypass.
  • Bay Delta Conservation Plan : the Yolo Bypass Fisheries Enhancement Planning Team is recommending changes to the Fremont Weir and Yolo Bypass to make them more fish friendly.
  • USBR/DWR Yolo Bypass Implementation Plan: currently in a scoping period until April 4, 2013, the USBR is inviting comment on their proposed plan to meet the requirements under the 2009 Biological Opinion to improve fish passage and habitat for endangered salmon and sturgeon.

We are fortunate that in the early 20th century, after a series of mega-storms, planners had the foresight to create these managed floodplains to deal with flood waters.  Now they give us the opportunity to explore changing their management to recreate the ecological functions that the levee system destroyed.  They already provide agricultural and waterfowl value, now they may also be a lifeline for fish.




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