A flash flood is a rapid flooding of geomorphic low-lying areas: washes, rivers, dry lakes and basins. Flash floods kill more people than Hurricanes. Water moving at 4 miles per hour exerts a force of about 66 pounds on every square feet of anything it encounters. Flash floods may occur after the collapse of a natural ice or debris dam, or a human structure such as a man-made dam, as occurred before the Johnstown Flood of 1889.
Presentation on Flash Floods
