Hurricane Floyd: Sep-99, 18,599, $439

Hurricane Irene: Oct-99, 13,651, $118

Florida Flood: Oct-00, 9,220, $157

Tropical Storm Allison: Jun-01, 30,270, $1,095

Tropical Storm Gabrielle: Sep-01, 2,072, $30

Texas Flood: Jul-02, 1,815, $69

Tropical Storm Isadore: Sept-02, 8,224, $108

Hurricane Lili: Oct-02, 2,529, $35

Texas Flood: Oct-02, 2,797, $80

Hurricane Isabel: Sep-03, 19,389, $446

Hurricane Charley: Aug-04, 2,004, $33

Hurricane Frances: Sep-04, 3,557, $77

Hurricane Ivan: Sep-04, 10,828, $347

Hurricane Jeanne: Sep-04, 1,762, $24

Source: Federal Emergency Management Agency

The Associated Press reported that the heaviest flooding was concentrated in the area where Nevada, Arizona, and Utah meet. The most catastrophic event, however, occurred at La Conchita in California's Ventura County, where a bluff collapsed, crushing 15 homes and killing 10 residents. Hundreds of families throughout the four states have been left homeless.

Flooding may be triggered by hurricanes, changes to tropical storms, or nothing but heavy rain in some states, FEMA noted. Although 2004 was a bad year for floods in the United States, primarily due to the hurricane activity in the Southeast, California had not seen significant flooding since January 1998. The agency describes a significant event as one with 1,500 or more losses paid by the National Flood Insurance Program.