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Overview: The Corps in the Delta

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The Sacramento-San Joaquin River Delta, also known as the California Bay Delta, is the West Coast’s largest estuary; a critically-threatened and nationally-significant ecosystem and the heart of California’s water supply system that serves as many as 25 million people.

The Delta is a web of channels and reclaimed islands at the confluence of the Sacramento, San Joaquin, Cosumnes, Mokelumne and Calaveras rivers, and the outlet for Central Valley rivers to the San Francisco Bay. Much of the land is below sea level and is outlined by a network of 1,100 miles of levees constructed during the past 150 years to manage the flow of water through the Delta. The network is a mix of federal and non-federal levees and most do not meet Corps levee construction standards and could fail at water levels well below the top of the structures.

Historically, the Delta was defined by tidal wetlands, primarily comprised of peat soils. The Swamp and Overflow Land Act of 1850 transferred ownership of all swamp and overflow land, including Delta marshes, from the federal government to private parties. This Act triggered the reclamation of wetlands in the Delta through the construction of levees and drainage channels, typically by the new land owners. The majority of levees in the Delta are still privately owned and maintained. Nearly three fourths of the Delta is now in agriculture. Nearly 95 percent of the historic wetland habitat in the Delta has been converted to agricultural and urban uses.

Native habitat and natural river function in the Delta have been degraded by construction of the levee network and conversion of the floodplain to agricultural and rural development, as well as management of the system for municipal, industrial and agricultural water supplies.

The Delta was named an ecosystem of national significance. It is a critical link in the Pacific Flyway, a major north-south route of travel for migratory birds in America, and is protected through the Migratory Bird Treaty Act of 1918.

Natural resource specialists agree that the remaining ecosystems in the Delta no longer maintain the functions and richness that defined the pre-channelized system, and that the measures of ecological health will continue to decline without preventive action. Not only is it certain that these natural systems will not recover their defining attributes under current conditions, it is unlikely that even the current, degraded ecological conditions can be sustained into the future.


Concern elevated during the 1990s that widespread failure of Delta levees – especially after an earthquake – could cause salt water from San Francisco Bay to intrude into the Delta, effectively shutting down water supply for the 25 million Californians who depend on water pumped from the Delta. This concern resulted in two broad Corps initiatives.

First, to address the immediate threat of levee failure, Congress authorized the CALFED Levee Stability Program, which provided funding for a suite of individual levee fixes to quickly shore up weak spots. While that program produced 31 reconnaissance-level reports for individual projects, and funded the completion of the Delta Flood Map Book, it has not resulted in any projects moving toward construction. Its remaining appropriated funded is being used to further improve Corps and state Delta flood emergency response coordination under a memorandum of agreement with DWR.

Second, the Delta Islands and Levees Feasibility Study (Delta Study), is the Corps’ mechanism to participate in a cost-shared solution to address ecosystem restoration and flood risk management in the Delta and Suisun Marsh area. A feasibility cost-share agreement was executed in May 2006 with the California Department of Water Resources, the non-Federal sponsor for the study.


The Corps is concurrently a cooperating agency in reviewing the State of California's Bay Delta Conservation Plan ahead of eventual permitting that must be processed for regulatory and navigation/levee safety impacts. Comments on the public draft of the BDCP are due in June 2014.


Flood Emergency Response Map Book

image - page from flood emergency response map book

Produced with the California Department of Water Resources in 2011, this map book provides a working framework to aid each Delta community in their emergency response planning.

A digital version may be downloaded HERE. (File size 180MB)


Delta Islands & Levees Feasibility Study

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This feasibility study is the Corps’ mechanism to participate in a cost-shared solution to a variety of water resources needs for which we have the authority. Results of the Department of Water Resourcess' (DWR) Delta Risk Management Strategy (DRMS) studies will be used to define problems, opportunities, and specific planning objectives.

The feasibility study will address flood risk management, ecosystem restoration, water quality, water supply, and a variety of other issues. A feasibility cost-sharing agreement (FCSA) was executed May 26, 2006 with DWR, our non-Federal sponsor.

The total cost of the feasibility study is currently $12,000,000; cost shared 50/50 with the California Department of Water Resources.

FY 08 appropriations at $859,000

FY 09 appropriations at $478,000
  -Reprogrammed additional $150,000

FY 10 appropriations at $394,000

FY 11 appropriations at $239,000

FY 12 appropriations at $971,000

FY 13 appropriations at $1,012,970

FY 14 appropriations at $447,000


Delta Study -- Send your comments

Submit your comments regarding the Delta Study via email to