Monday, May 21, 2012

Racing to fix California levees before the big one hits

Jeremy Miller on For those who know little about the massive estuary an hour east of downtown San Francisco, the Delta is the meeting place of two of the state’s largest river systems, the Sacramento and San Joaquin. Flowing down from Sierra snowfields and lakes, the two rivers converge in this 1600-square-mile tangle of tidal marshes, sloughs and canals.

As California’s population and economy has grown, so has demand for water, much of which is pumped from the Delta and delivered throughout the state by way of sprawling networks of reservoirs, canals and aqueducts. (For more on the Delta’s geography and history, see the interactive map and presentation accompanying the report.)

A key challenge examined in Sommer’s report is the issue of sea level rise, which makes the Delta’s aging and subsiding 1100-mile levee system increasingly vulnerable to flooding and failure. The threat is magnified by the risk of a major earthquake, which by most accounts the Bay Area is due for. For example, in 2009, the US Geological Survey predicted that there is a 62% chance of a 6.7-magnitude or greater earthquake striking the Bay Area in the period between 2003 and 2032.

...A levee failure could result in a rush of saltwater into the Delta, a scenario sometimes referred to as the “big gulp.”...

Image of head of Old River along lower San Joaquin River provided by M.Burns (CADWR) for release into public domain by MCalamari

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