James S. Aber
Flooding becomes a hazard when high water leads to human casulties, damage to structures, and impairment of human landuse. Development of drainage basins for shipping, agriculture, water resources, recreation, and urban growth often leads to increased frequency and larger magnitude of flooding. Flood water usually contains much fine sediment along with raw sewage, oil, grease, and other insoluble compounds, animal carcasses, insect eggs, weed seeds, floating debris and many other dangerous or undesirable materials. Erosion and deposition of sediment may cause permanent changes in channel and basin geomorphology.
Rivers and streams serve two basic functions in the landscape--to remove excess surface water and to carry away sediment. Any human modifications of the stream channel or drainage basin inevitabiliy lead to changes in the hydrologic and sedimentologic regimes of the stream. Such changes may benefit certain segments of society while proving deleterious for other economic or recreational interests. Thus, implementing stream and river control is a complex societal issue in the modern world. Floodplain wetlands often play a significant role for lessening the impact of downstream flooding.
|Flooding on the Cottonwood River, Kansas.|
|1993 flooding in the upper Mississippi basin.|
|1997 flooding in southern Poland.|
Return to wetlands syllabus.