Simi Valley residents will get their first look tonight at a map that shows which areas of the city would be threatened by a once-in-a-century flood, and whose insurance requirements might rise as a result.
The new flood plain map, produced by the Federal Emergency Management Agency, shows where flooding would occur when water rises to a level it is expected to reach only once every 100 years. The map is tentative, and FEMA is not expected to adopt a final version until October.
Neither FEMA nor the city has calculated the acreage of the newly measured flood plain, nor the number of people living in it.
A 1974 study by the U.S. Army Corps of Engineers showed that 250 Simi Valley residences are in the flood plain. But because of growth and topographical changes, "now, we're talking about many thousands," Mike Kuhn, senior planner for the city, said.
Ray Lenaburg, a senior FEMA engineer, is scheduled to explain the map and its implications at a 7:30 p.m. public session in the Simi Valley City Council chambers, 2929 Tapo Canyon Road.
The chart shows that large areas of the city would face flooding, but it does not differentiate between sections where water more than a foot deep is expected and places where less severe conditions would prevail. That distinction is crucial to people who might be required by law to buy flood insurance.
Anyone who buys, refinances or borrows against real estate through a federally insured lender is required by law to purchase flood insurance if the property could be under a foot or more of water in a 100-year flood. People who already own their residences need not buy insurance if they do not take out new loans on the property.
Simi Valley is the only community in California, and one of only a handful nationwide, for which FEMA does not yet have a detailed flood plain map, officials said.