How Often Do Floods Occur?
The frequency of flooding depends on the region, although it is one of the most common natural disasters in the United States. Floodplains can flood every year, and floods are more common in the Midwest and coastal regions.
The frequency of flooding depends, in part, on the type of flood; the four main types are overbank floods, flash floods, ice jam floods and coastal floods. Coastal flooding occurs when storm fronts move ocean water inland and can occur several times a year. Often, this type of flooding is only considered nuisance flooding because it does no more than close roads and overwhelm storm drains. However, coastal flooding during hurricanes can cause serious damage and even death. As of 2015, the frequency of coastal flooding has increased between 300 and 925 percent since the 1960s.
Flash floods cause more deaths than any other weather-related problem in the United States. Flash floods occur suddenly during periods of intense rainfall that the soil can't absorb. Walls of water can reach up to 30 feet high, wiping out bridges and triggering mudslides. Overbank flooding occurs mostly in the Midwest when water creeps over river banks. Usually, these floods don't last long or cause much damage. Sometimes, flooding occurs when levees and dams break.