Delta Levees

Output Performance Measure 7.3, Last updated: September 14, 2023 | About this Measure
Improve levee infrastructure to meet current safety standards and reduce flood risk.

The Measure

Delta levees reduce the flood-related risk to people, property, and state interests in the Delta.

  • Expectations

    Levees in the Delta will be improved over time to reduce the risk to people, property, and state interests in the Delta.

  • Performance Metrics

    • Percentage of urban communities in the Delta protected by levees meeting DWR’s urban level of flood protection criteria.
    • Percentage of rural Delta islands and tracts protected by levees at or above the Bulletin 192-82/PL 84-99 standard.

Rural Delta Islands Protected By Levees

Delta islands and tracts protected by levees meeting the Bulletin 192-82/PL 84-99 standards (left). Percentage of rural islands meeting the Bulletin 192-82/PL 84-99 standards (right).

Data for the evaluation is from 2012. However, new data is being gathered using Light Detection and Ranging (LIDAR) techniques by United States Geological Survey (USGS) and the Department of Water Resources (DWR) that will allow updated evaluations of levees in the system.

Click a rural island to see if its levees met target standards.

Urban Levees in the Delta

Although most Delta levees are rural (such as those pictured in the map above), there are six levees in the Delta that protect urban areas. Because of the density of people and property behind those levees, special standards have been developed for them.

A levee with a city behind it.
Six Delta levees protect urban areas such as Stockton and West Sacramento.

Urban Levee Design Criteria

As a part of FloodSAFE California, the Department of Water Resources entered into a comprehensive statewide flood planning initiative. One outcome of that process was developing a report in May of 2012 that set criteria for urban levees. These standards are known as the Urban Levee Design Criteria (ULDC) and provide specific engineering criteria for levees. As a part of the Delta Levee Investment Strategy (DLIS), the six urban levees in the Delta were evaluated based using ULDC. The July 2017 report concluded that improving those levees to ULDC standards would reduce fatality risk and property damage risk by more than 50 percent.

Search by Island

Search by Island to see if levee standards were met in 2012 and if the target for the levee was rural levee standards or urban levee standards.

Next Data Update: DWR is producing new levee data using 2017 LIDAR data, anticipated by the end of 2021.

The Delta is an inherently flood-prone area. Historically before the Delta was modified with levees and other human structures, the Delta’s low-lying islands and floodplains overflowed with rivers' natural flows for long periods each spring. Today, levees within the legal Delta protect approximately 740,000 acres of land. Many Delta levees protect land below sea level, they hold back water all day, year-round, rather than only during floods, and are called "the hardest working levees in America” (Delta Plan 2013).

Reducing flood risks to people, property, and state interests is critically important in the Delta and levees play a major role in flood-related risk reduction. State and federal guidelines and criteria establish minimum criteria for levee design and maintenance. The Public Law 84-99 (PL 84-99) standard is a minimum requirement established by U.S. Army Corps of Engineers (USACE). USACE developed a Delta-specific standard based on the Delta particular organic soils and levee foundation conditions. 

Levees in the Delta will be improved over time to reduce the flood-related risk to people, property, and state interests in the Delta. This measure tracks the quality of Delta levees against predominant levee standards.

Each chapter of the Delta plan includes strategies to achieve the goals of the plan. These strategies are general guidance on achieving the objective laid out in the plan and in the Delta Reform Act of 2009. Associated with these strategies are recommendations. Strategies may also have associated performance measures. Delta Plan performance measures track progress in achieving desired outcomes for the Delta Plan. Below is the strategies associated with this performance measure. 

Delta Plan Strategy

  • Prioritize Investment in Delta Flood Management

Metric
  • Percentage of urban communities in the Delta protected by levees meeting Department of Water Resources (DWR) urban level of flood protection criteria. This will be evaluated at least every five years.
  • Percentage of rural Delta islands and tracts protected by levees at or above the Bulletin 192-82/PL 84-99 standard. This will be evaluated at least every five years.
Baseline
  • Percent of urban area in the Delta protected by levees, meeting DWR’s urban level of flood protection criteria, as of completion of the Delta Levees Investment Strategy.
  • Percentage of rural Delta islands and tracts protected by levees at or above the Bulletin 192-82/PL 84-99 standard, as of completion of the Delta Levees Investment Strategy.
Target
  • 100 percent of urban communities in the Delta are protected by levees meeting DWR’s urban level of protection criteria, demonstrated by 2025.
  • 100 percent of rural Delta islands and tracts are protected by levees at or above the Bulletin 192-82/PL 84-99 standard, demonstrated by 2050.
Data Source

Data is from the Delta Levee Investment Strategy (DLIS)

Spatial data of the Delta levees 

Delta Levee Investment Strategy

MyHazards from the California Office of Emergency Services

The Delta Levees Maintenance Subventions Program from the Department of Water Resources

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