"The federal government has informed property owners in more than 150 cities and unincorporated areas in Los Angeles, Orange, Ventura, Riverside and San Bernardino counties about the new requirement. Most live near rivers and creeks, below dams or in low- lying areas that are at greater risk of flooding than previously believed, according to maps developed by the Federal Emergency Management Agency.
Premiums range from $500 to more than $1,700 a year. Insurance is mandatory for anyone with a federally backed mortgage, and lenders will typically buy policies, sometimes at a higher cost, for property owners who fail to do so on their own. Fannie Mae and Freddie Mac own or guarantee more than half of all U.S. mortgages."
FEMA has been redrawing flood maps all over the country since 2003 in an effort to identify areas prone to risk during a 100-year storm event. Some Southern Californians affected by the new maps are planning to challenge the Agency's redrawing.