LYCOS RETRIEVER 
Floods: Flash Floods
built 640 days ago
There are three major types of floods: river floods, flash floods and coastal floods. River floods are caused by high or overflowing water from a river and typically occur after winter and spring rains and when snow is melting. (Flood and Flash Flood Occurrence) This water is directed to a major stream from its drainage basin. (Nuhfer, Proctor, and Moser) River floods can ... occur when ice or floating debris cause a jam. (Flood and Flash Flood Occurrence) The debris flows tend to occur primarily in the summer. Intensive snowmelt in the mountains causes the debris to flow in the spring and rapid thawing glaciers cause the problems that happen during the summer.
Source:
Ice-jam floods occur on rivers that are totally or partially frozen. A rise in stream stage will break up a totally frozen river and create ice flows that can pile up on channel obstructions such as shallow riffles, log jams, or bridge piers. The jammed ice creates a dam across the channel over which the water and ice mixture continues to flow, allowing for more jamming to occur. Backwater upstream from the ice dam can rise rapidly and overflow the channel banks. Flooding moves downstream when the ice dam fails, and the water stored behind the dam is released. At this time the flood takes on the characteristics of a flash flood, with the added danger of ice flows that, when driven by the energy of the floodwave, can inflict serious damage on structures.
Source:
The third major type of flood, coastal floods, occurs when strong offshore winds that push water from an ocean on to the land. (Flood and Flash Flood Occurrence) Low barometric pressure in storms like hurricanes cause the sea level to rise locally above the coastal lowlands. (Nuhfer, Proctor, and Moser) Eventually storm surges are produced. (Flood and Flash Flood Occurrence) Coastal areas are often barrier islands, swamps and plains with many rivers. The additional rainfall in these areas increases flooding in the surrounding low lying areas. (Flood Climatology) The overflowing seawater then rushes in to the mouths of river channels and covers the area with water.
Source:
February 14, 2006 - Flash floods can strike any time and any place with little or no warning. In mountainous or flat terrain, distant rain may be channeled into gullies and ravines, turning a quiet streamside campsite or wash into a rampaging torrent in minutes. City streets can become rivers in seconds. Observe these flash flood safety rules. They could save your life.
Source:
Most flash floods are caused by slow-moving thunderstorms, or thunderstorms which move over the same area one right after the other. Flash floods generally occur within a short time period after a rain event - generally 6 hours or less. For this reason they are more life threatening. Areas most susceptible to flash flooding are mountainous streams and rivers, urban areas, low-lying area, storm drains, and culverts.
Source:
Water-weary residents across the Midwest began counting their losses Tuesday as damage estimates from this weekend's deadly flash floods climbed into the tens of millions. The rain moved into Ohio, where roads flooded, schools canceled classes and residents were rescued from flooded homes by boats.
Source:
MORE ABOUT
Flash Floods