| Flash floods - rapid rises in water levels with high flow | | | | dry to quickly absorb the water and the lack of plant |
| velocities - can occur in a matter of seconds. Factors | | | | life to slow the water's course. |
| such as rainfall intensity and duration, as well as | | | | Areas with a high risk of flash floods (such as the land |
| regional topography, can all contribute to a flash flood | | | | surrounding large dams) often have warning systems |
| situation. Urbanization is also an important cause of | | | | in place to help alert the population in advance of a |
| flash floods. The roofs, sidewalks, and roads of a city | | | | flood. The forecast center for your region calculates |
| create dangerous amounts of runoff water during big | | | | flash flood guidance for all the bodies of water in the |
| storms, and this runoff can easily become a flash flood | | | | area. Flash flood guidance is the amount of rainfall for |
| if an adequate storm sewer system is not in place. | | | | a given duration necessary to produce flash flooding. |
| In mountainous regions the rainfall can run down a | | | | With these figures readily available, weather services |
| steep mountain and pick up so much speed that it | | | | can provide predictions and early warnings to give |
| becomes a dangerous wave moving too fast for | | | | inhabitants of the region time to move to higher ground. |
| people to escape. A similar situation occurred in Rapid | | | | If you live in a region that is prone to flash floods, make |
| City, South Dakota, in 1972 when 237 people were | | | | sure you have a map to the quickest region of high |
| killed. | | | | ground. Also, make sure you monitor weather service |
| Even deserts are not immune to flash flooding. Dry | | | | announcements during big storms in case of a flash |
| riverbeds can channel water long distances and create | | | | flood warning. |
| dangerous flood waves, due to the ground being too | | | | |