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Delta Subsidence and Levee Safety

From: Our Changing Climate 2012: Assessing the Risks to California (pdf)

The Sacramento-San Joaquin Delta is a critical freshwater resource for California and its reliability depends significantly upon the integrity of the earthen levees protecting dozens of Delta islands. These levees protect not only much of the state’s water supply, but also important energy infrastructure such as underground natural gas storage fields, pipelines and transmission lines. Farmland, homes, and endangered species are also at risk. In the event of a levee failure — whether as a result of an earthquake or overtopping during storms — brackish water would fill the Delta lowlands and rapidly degrade freshwater quality and supplies and threaten the other assets. Consequently, it is critical to monitor the relationship between levee elevations and sea level. The island interiors have sunk from elevations near sea level at the end of the 1800s to current elevations as much as 15 feet below sea level. Sinking (or “subsidence”) of delta islands has been attributed historically to compaction and loss of peat soils drained for agricultural purposes. A new study using satellite radar data finds that in addition to localized subsidence, the entire Delta may be sinking.  Land subsidence together with rising sea levels may cause water levels to reach dangerous levels as early as 2050. However, ongoing monitoring of levee heights may provide sufficient advance notice to prioritize and take necessary protective measures.

Post last edited on: 2013 December 05

Tags: transportation, water

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