Floods can be slow, or fast rising but generally develop over a period of days. Dam failures are potentially the worst flood events. A dam failure is usually the result of neglect, poor design, or structural damage caused by a major event such as an earthquake. When a dam fails, a gigantic quantity of water is suddenly let loose downstream, destroying anything in its path. Flash floods usually result from intense storms dropping large amounts of rain within a brief period.
Flash floods occur with little or no warning and can reach full peak in only a few minutes.
Communities particularly at risk are those located in low-lying areas, near water, or downstream from a dam.