9781422269541

the world that receives rain, 23% of the world's population is exposed to flooding. In the United States, 13% of the population is at risk of experiencing a coastal or inland flood. Floods are most common in river plains and coastal areas, and they put communities in low-lying areas, near water, or downstream from a levee or dam at risk. Densely populated areas are at a higher risk for flash floods because construction of buildings, highways, driveways, and parking lots increase runoff by reducing the amount of rain that can be absorbed into the ground. Camping or recreational areas along a stream or river can be hazardous if there are thunderstorms in the area. Sometimes thunderstorms cause flooding far upstream, and people downstream are unaware of the danger until they see the floodwater.

Cities that are close to sea-level elevation have levees like this one to protect from flooding. When levees break, flash floods can occur quickly due to the sudden release of water.

13

What Makes a Flood