An aerial view of the Lookout Slough Tidal Habitat Restoration and Flood Improvement Project in Solano County.

Delta Levees: The Backbone of the Coequal Goals

October 25, 2024

By Julie Lee, Erin Mullin, and Amanda Bohl

From above, the Sacramento-San Joaquin Delta’s levee system resembles a maze of winding earthen berms stretching for miles. From that perspective, the levees may look small and insignificant, but they play a crucial role in holding back water to protect homes, agriculture, wildlife, and the water supply for millions of Californians.

Did you know?

Levees are vital to furthering the coequal goals of water supply reliability and ecosystem health while protecting California’s Delta as an evolving place.

Levees reduce flood-related risks to people, property, and state interests in the Delta.

With climate change, it is even more critical that these levees be maintained and improved.

In fact, levees are the backbone of the Delta. They are vital to furthering the coequal goals of water supply reliability and ecosystem health while protecting California’s Delta as an evolving place. Approximately 700,000 acres of land are supported and protected by levees, which also provide multiple benefits:

  • Fish and Wildlife: vegetation on levees provide habitat for birds and shade to cool the water for fish
  • Agriculture: levees protect farms, enable drainage, and incorporate irrigation and water control facilities
  • State Infrastructure: levees protect major highways, roads, utility lines and conduits, and public facilities
  • Water Supply: levees create channels that protect and carry fresh water from upstream of the Delta to the pumps in the southern Delta
A photo from the California Department of Water Resources of Highway 12 just east of the Rio Vista Bridge was blocked by floodwaters after a levee failed in the vicinity of the Spindrift Marina on June 21, 1972 in the Brannan-Andrus Levee Maintenance District. A Federal Disaster was declared on June 27 within the Sacramento-San Joaquin Delta region. The levee repair was conducted by the U.S. Army Crops of Engineers and the breach was closed on July 26. Photo taken June 23, 1972.

The construction of Delta levees began in the 1850s. By the 1920s, most of what had once been a network of seasonally inundated low-lying islands had been diked and turned into farmland. Local reclamation districts managed the levees, largely unaided, until 1972, when a catastrophic levee failure on Brannan Island disrupted water exports for over a month. In response, the state began investing in Delta levee maintenance and improvements. Since that time, state investments have greatly reduced the chance of levee failure; however, flood risk remains.

Delta levees and the governing bodies that manage them create a complex system. Delta levees can be publicly or privately owned, and all Californians benefit from the multiple benefits they provide.

In recognition of both the local and statewide significance of the Delta’s levee system, the Delta Plan states that reducing flood risks to people, property, and state interests is critical. Delta Plan regulations, recommendations, and performance measures promote risk reduction through strategic investments in structural and nature-based measures to reduce flood risk, such as targeted levee investments and promoting effective adaptation.

In 2024, the Delta Stewardship Council enacted the Delta Levees Investment Strategy (DLIS), a risk-based prioritization strategy for Delta levees with the goal of maximizing flood protection for people, property, and state interests. DLIS directs the Department of Water Resources (DWR) to fund levee improvement projects based on a risk-based priority system; and DWR prepares an annual report to the Council.

Glossary

Delta Plan: A comprehensive, long-term, legally enforceable plan to guide how multiple federal, state, and local agencies manage the Delta’s water and environmental resources.

Project levee: Levees owned by the federal government, for which the state has given assurances to operate and maintain in accordance with the structures’ Operations and Maintenance Manual.

Non-project levee: Local flood control levees in the Delta that are not a project facility. Most of these non-project levees are maintained by local reclamation districts created and funded by landowners.

Levee maintenance and funding are also complex. Maintenance is provided by public levee districts, local governments, private levee owners, and, in certain cases, DWR (collectively known as Levee Maintenance Agencies or LMAs).

Funding for levee maintenance comes from two sources: local government and state government. Multiple programs exist (please see Delta Levees Information Sheet for more information) to help support levee maintenance but there are several challenges:

  • The financial burden is often placed on local levee maintenance organizations despite the fact that their levees support more than local needs; and
  • Reimbursements are slow, stretching the finances of local levee maintenance organizations.

The Delta Plan Interagency Implementation Committee (DPIIC) will be highlighting levees at its October 28, 2024 gathering.

Representatives from many local, state, and federal agencies will share their perspectives on levee maintenance, funding, seismic concerns, vegetation on levees, and more. We’ll also discuss how the DPIIC agencies can work together to simplify and increase the reliability of funding so that needed levee maintenance and improvements can happen. Information about the October 28 gathering is available on the Council’s website. Please join us.