Floods

Floods are the number-one natural disaster in the United States in terms of number of lives lost and property damage. Floods can occur at any time of the year, in any part of the country. For the past 30 years, the U.S. has averaged 82 deaths per year from flooding, which is second only to heat-related deaths among natural disasters.

Image source: Rosenberg Library (Galveston) in Mason, Herbert. Death from the Sea. Dial Press, 1972.

Sources of Flooding

There are many sources of flooding: heavy rainfall overwhelming waterways; dam and levee failures; and hurricane storm surges. The deadliest natural disaster to strike the U.S. was the hurricane and its storm surge that devastated Galveston, Texas, on September 8, 1900. Powerful winds combined with a 15-foot storm surge flooded the city, killing over 6,000 people and destroying nearly all homes on the island.

Measuring floods

In the Midwest, floods are usually the result of heavy rainfall inundating rivers and streams. To monitor flooding, scientists at the U.S. Geological Survey (USGS) check data from fixed measuring sites. In Kansas, data are collected at 180 sites. In Missouri, the USGS has 265 sites. Gages at those sites measure the height of the water (also known as gage-height or stage) and streamflow.