Flash Flood Safety
There are several kinds of floods.
The "traditional" flood
results from days of heavy rain and/or melting snow, with rivers gradually rising and
going over their banks. These can usually be predicted with considerable accuracy,
providing adequate warnings that result in saving lives and reducing loss of
Flash floods are a different matter. They usually result from rapidly changing weather situations, such as the sudden development of an intense local storm over the drainage basin of a small stream or river. Rivers can rise way above flood stage in a matter of hours if not minutes. However, not all flash floods are caused directly by heavy rain. Ice and log jams can suddenly let loose huge torrents of water. Natural or constructed dams can collapse due to earthquakes or mudslides.
Why do so many people die in flash floods? Aside from the factor of surprise (many people are caught sleeping), people just don't appreciate the power of moving water. Even six inches of fast-moving flood water can knock you off your feet. Most automobiles will float and can be swept away in only two feet of water. Never try to walk, swim, or drive through the swift currents of a flash flood. Nearly half of all U.S. flash flood fatalities are auto related. Never attempt to drive over a flooded road. The depth of water is not always obvious. Also, the road bed may have been washed out under water. Dry creek beds can go from dusty bone dry to a ten-foot-deep torrent of water within a minute as the thunderstorm rains drain down from surrounding higher terrain.
Back to Thunderstorms and Associated Weather Phenomena.