科研之友
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摘要
The historical removal of accumulations of wood on medium to large rivers in the continental United States caused a fundamental change in river corridors that has received relatively little attention in the scientific literature. Although scientific literature discusses the natural wood rafts present on the Red and the Atchafalaya Rivers in the southeastern United States, there is little awareness that similar extensive masses of wood are documented in the historical record from forested river catchments as diverse and widespread as those in the northeast, southeast, Texas Gulf Coast, Pacific Northwest, and upper Great Lakes regions of the country. While present, these natural wood rafts decreased channel conveyance, increased channel-floodplain connectivity, and facilitated anastomosing channels and floodplain lakes. Removal of natural wood rafts began in the 17th century in the eastern United States and proceeded westward with the movement of European settlers, accelerating during the 19th-century era of steamboats and floating of cut timber. Removal of the natural wood rafts likely forced many rivers from a multi thread planform with high channel-floodplain connectivity into an alternative stable state of single-thread channels with substantially reduced overbank flow, sedimentation, and avulsions. There is now widespread recognition among the geomorphic community of how upland clearance increased sediment yields and floodplain aggradation. I propose that widespread removal of instream wood for steamboat routes, timber rafts, and flood control was equally significant in decreasing floodplain sedimentation and river complexity, and in causing a fundamental, extensive, and intensive change in forested river corridors throughout the United States.
- 出版日期2014-10
