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in the direction of the treatment plant. During power outages, these pumps stop working, which can cause the sanitary sewers to back up. A storm sewer can also back up if there is a large amount of water flowing through it and it is unable to contain it all. Flash floods can happen without warning and are characterized by a raging, strong, fast-moving stream of water. Flash floods are responsible for the greatest loss of life and are caused by slow-moving thunderstorms, heavy rain from hurricanes or tropical storms, floating debris, ice jams, or breaks in an embankment , levee or dam . Very dry areas are more prone to flash flooding when significant rainstorms strike because the Charleston, South Carolina, has very low elevation and its coastline is highly developed, as pictured here. The homes and other buildings do not allow for shielding against powerful nor’easters and the coastline here floods several times a year.

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What Makes a Flood