In this story from the San Jose Mercury News we are reminded of the impact even a small earthquake could have on aging levees, and points up the necessity to consider earthquake resistant large concrete dams as a stronger back-up for any flood conditions rising from earthquakes.
Here is an excerpt.
Quake could break levees
LIKELIHOOD SMALL; EFFECT WOULD BE HUGE
By Lisa M. KriegerMercury News
Even a moderate earthquake could cause California's aging levee system to collapse, flooding 400,000 homes and sending brine into the drinking water of homes across Northern California.
According to a computer-generated study presented Wednesday at Stanford University, a 6.5 magnitude quake in the area of Antioch and Rio Vista could trigger the breaching of as many as 50 levees in the southwestern regions of the Sacramento Delta.
``Your levees are not seismically safe. They're just piles of dirt,'' said retired Brig. Gen. Gerald Galloway of the U.S. Army Corps of Engineers.
Drinking water and farm water exports to Santa Clara County from the Delta would halt immediately. Damage could cause the aqueducts that carry water to the Bay Area from the Sierra Nevada to fail.
Two-thirds of Californians depend on the Delta for at least some of their drinking water. While Santa Clara County could rely on its reservoirs for a while, they are insufficient to serve the entire population indefinitely, said Martin McCann Jr., a consulting professor of civil and environmental engineering at Stanford.
McCann helped lead the study, which the California Department of Water Resources launched after Hurricane Katrina. The goal was to help the state calculate the effect of a major earthquake or winter flooding in the Delta region.
