I should point out that things like this have already happened, on the small scale, in and around the Delta. For example, South Modesto flooded a few years ago when the Tuolumne River crested at the _500-year flood stage._ The greater region got seven inches of rain in three days (can you say "Pineapple Express?"), and the dam upstream of the Tuolumne overfilled and starting releasing excess water downstream in the middle of the storm.
As in New Orleans, the human factor actually increases the risk of flooding. The whole delta used to flood annually back before the middle of the 1800s, but settlers built levees and later dams for flood control. The problem with dams here is that they serve two or more purposes that conflict: flood control, water storage for cities and agriculture, and sometimes recreation. Dam operators don't always draw down reservoir levels far enough to protect against serious storms, because they're worried about maintaining sufficient water supply throughout the coming year. So when serious rain and runoff hits a dam whose operator has kept the reservoir high for strategic reason, he may have no choice but to release extra water downriver _in the midst of flood conditions._
Same thing happened about ten years back in San Jose, when the Guadalupe Riveroverflowed and flooded several neighborhoods because Lexington Reservoir, up by Los Gatos, overfilled during a big storm and had to dump extra water down the river while the storm was still going on. Since then, I've noticed that the Lexington operators draw down that reservoir pretty far during the summer, I assume to avoid future problems. And they've been lucky enough to get enough rain each winter to fulfill their city water commitments.
Last edited by Rodney; 02-19-2006 at 07:47 AM..
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