Geologic and geomorphic controls of alluvial island location in Cheat River, West Virginia.

摘要

Cheat River of north central West Virginia and southwestern Pennsylvania is a stable moderately sinuous mountain river with numerous anabranching reaches that include 81 alluvial islands. Relatively stable features, Cheat River alluvial islands are characterized by woody vegetation or human habitation, an elevation equal to or greater than the surrounding floodplain, and a perennially exposed emergent surface surrounded by active channels. Valley geometry, lithology, and tributary input are the main geologic and geomorphic controls selected to assess island location in Cheat River. Islands are more numerous in wide valleys with extensive floodplains; these valleys occur in lithologic segments dominated by less resistant bedrock. Islands occur at 25 percent of tributary mouths; however, only nine percent of the tributaries appear to be the main factor contributing to island location. Cheat River consists of seven lithologic segments made up of 19 sub-segments. Islands are most common in areas where floodplains are extensive and active. Island location, shape, and geomorphic expression suggest islands originate from many different mechanisms.