Knowra Flash flood Flash flood A rapid, localized flood that develops within hours, often after intense rainfall or a sudden release of stored water. Its short onset leaves little time for warning or evacuation.
Hydrology : The study of water movement, distribution, and properties on Earth and elsewhere. Flash floods are rapid hydrologic events shaped by runoff and flow through a catchment.
Convective precipitation : Rainfall produced when warm, moist air rises, cools, and condenses in convective clouds. Slow-moving or repeated thunderstorms can deliver intense rain over a small area.
Flash flood warning : An official alert that dangerous flash flooding is occurring or imminent in a specified area. Warnings communicate immediate danger when rapid rises leave little time to respond.
Flood mortality : Deaths caused directly or indirectly by flood events. Sudden onset and powerful currents make flash floods especially dangerous to people in their path.
Big Thompson Canyon flood : A catastrophic flash flood in Colorado on July 31, 1976, caused by intense rainfall in a narrow canyon. The event illustrates how a sudden storm and confined terrain can trap people in rising water.
Rainfall intensity : The amount of rain falling per unit of time, commonly measured in millimeters per hour. Very intense rainfall can exceed the ground's capacity to absorb or drain water.
Atmospheric river : A long, narrow region of the atmosphere that transports large amounts of water vapor. Atmospheric rivers can bring intense precipitation that triggers rapid flooding in steep terrain.
Weather radar : A remote-sensing system that detects precipitation and estimates its location, movement, and intensity. Radar helps identify intense rainfall that may trigger flooding before gauges register rising water.
Debris flow : A fast-moving mixture of water, soil, rock, and organic material flowing downslope. Floodwater can entrain sediment and debris, greatly increasing its destructive force.
Johnstown Flood : The catastrophic 1889 failure of the South Fork Dam, which sent a flood wave through Johnstown, Pennsylvania. It demonstrates how dam failure can create a sudden destructive flood far downstream.
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