GEOG 1216 Chapter Notes -Dynamic Earth, Federal Emergency Management Agency, Hydrograph
Document Summary
Flooding can be defined as excess surface water on an area that is normally dry land. It occurs when more water enters an area than is able to leave in a certain period of time. Water initially arrives on land as precipitation (rain or snow). Some of this water will be absorbed into the soil and may be used by plants or percolate into the groundwater. Excess water will run over the surface of the ground as runoff, flowing downslope because of gravity. Channels begin to form along lines of lower elevation or more easily eroded material. These channels are progressively eroded by abrasion between the streambed and materials carried in the watercourse. Hundreds of tiny streams will likely carry water downslope in the upper reaches of a drainage basin, eventually combining together to form larger streams, and finally a river. A drainage basin is the area drained by one particular river or stream (figure 1).
