Delta Levees

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).

2023 data is based on Delta Reclamation Districts five-year plans submitted to DWR in 2023. Data from 2012 is from the Delta Levee Investment Strategy.

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

The Flood System Status Report Update (2022 FSSR) produced in 2022 by the California Department of Water Resources Levee Evaluations Program evaluates approximately 2,000 miles of levees in the Central Valley (approximately 1,580 miles of SPFC, or State Plan of Flood Control levees, and 420 miles of non-SPFC levees) including the urban levees in the Delta. Urban Levee Design Criteria (ULDC) were developed in 2012 as a part of FloodSAFE California, a comprehensive statewide flood planning initiative. Six urban levees identified in the Delta Levee Investment Strategy are evaluated against the ULDC standards in the 2022 FSSR report.

Search by Island

Search by Island to see if levee standards were met in 2012- 2023 and if the target for the levee was rural levee standards or urban levee standards. All blanks in the Percentage of Standards Met indicate that 2022-2023 data is not available for the island. Islands with asterisks indicate that the majority of the land is designated as a Floodway.

Next Data Update: All Delta levee districts are required to provide final five-year plans to DWR meaning the next round of plans will be due by the end of 2028. The Central Valley Flood Protection Plan update reports are released every 5 years, meaning that the next data update is expected by the end of 2027.

About the Measure

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. 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. 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). Bulletin 192-82 recommendations produce a levee that is like one built per the PL 84-99 guidelines, except that the design water level has a 0.33-percent (1 in 300) annual chance of occurrence as opposed to the 1.0 percent chance (1 in 100) PL-84-99 standard allows (California Department of Water Resources, 2023). USACE developed a Delta-specific standard based on the Delta particular organic soils and levee foundation conditions. For much of the Delta, there is little difference (e.g. a few inches) between the 1.0-percent (1 in 100) and the 0.33-percent annual chance of occurrence (California Department of Water Resources, 2023).

Delta Plan Strategy

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, Baseline, and Target

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 Sources, Collection, and Processing

Data Source

All Rural and urban levee data from 2012 is sourced from the Delta Levee Investment Strategy (DLIS). The Delta Levee Investment Strategy program also produced a risk- based prioritization for 2024.

The 2023 data for Rural Levee compliance is sourced from Delta Reclamation Districts five-year plans that are provided through the Department of Water Resources as regulated by the Delta Plan. The Cal. Code Regs Tit. 23 § 5012/ RR P1 policy requires: DWR to submit a written annual report to the DSC on State funds distributed or provided by DWR within the legal Delta make the report publicly available present the report to the DSC due no later than March 1 of each calendar year AND at least 45 days prior to the oral presentation before the DSC. This report will be tracking both PL 84-99 and Bulletin 192-82 data and reporting them interchangeably due to the small difference between the two standards and the limited data types available from DWR reporting across 2012 and 2023. The percentage of miles of Delta levee district in compliance with Bulletin 192-82 / PL 84-99 standards from the 2023 five- year plans were used for the most recent data update. PL 84-99 compliance data from the 2012 DLIS data were used for Delta islands that were not included in the five-year plans provided by DWR (see list below). For overall total (i.e. 100%) compliance rates, only rural islands with 100% compliance were considered in both the 2023 and 2012 datasets.

Data for the DSC’s Delta Urban Levee Design Criteria (ULDC) analysis was extracted from the 2022 Flood System Status Report Update (2022 FSSR). Levee segments located within the six Delta urban levee systems were evaluated for criteria compliance using the determination in the Overall Rating column. The performance criteria for categories used in these assessments are based on the USACE Engineer Manual (EM) 1110-2-1913, Design and Construction of Levees (U.S. Army Corps of Engineers 2000) and DWR’s ULDC and were therefore, deemed to be an accessible source of ULDC compliance data. These segments were weighed by total miles and then summed to obtain the total miles that were compliant with ULDC and overall percentage of island levees compliant with ULDC on a per island basis. The results were then compared to baseline DSC ULDC levels of compliance.

It should be noted that not all islands represented in the 2012 dataset were featured in the 2023 dataset. The islands that were not represented in the most recent dataset include: Canal Ranch, Drexler Pocket, Drexler Tract, Ehrheardt Club, Glide District, Holt Station, Libby McNeil, Liberty Island, Mossdale Landing, Paradise Junction, Pescadero District, Peters Pocket, Pico-Naglee Tract, Randall Island, Rio Vista, River Junction, Rough & Ready Island, Sargent Barnhart Tract, Shin Kee Tract, Stewart Tract, Upper Jones Tract, Walthall, Wetherbee Lake, Winter Island.