| Rivers can threaten riverside communities through bank erosion, deposition, and flooding, necessitating a thorough understanding of the response of river channels to natural and anthropogenic forces. Therefore, spatial and temporal changes in channel geometry and migration of the Susquehanna River in the Binghamton (NY) region, from 1937 to 2002, were examined, and their possible causes were assessed. Channel migration was measured in a Geographic Information System (GIS) from aerial photographs taken nearly every decade since 1937. Additional information about the ages of depositional surfaces was gained by measuring the age of trees on these surfaces. At-a-station hydraulic geometry at the USGS gaging station at Conklin, NY, was analyzed for the years 1985 to the present using USGS records of channel geometry and flow. Changes in the channel cross-sectional geometry from 1971 to 1998 at the Conklin and Vestal USGS gaging stations were also analyzed. The results of a previously published analysis of hydraulic geometry changes at Conklin and Vestal for the years 1938 to 1985 were also considered.; Long-term changes in channel cross-sectional geometry were minimal at Conklin and Vestal, the most notable change being an increase in cross-sectional asymmetry at Conklin during the seven years after construction of the Route 20 bridge. At Conklin, there was an increase in flow velocity and decrease in flow depth after de-snagging and clearing by the Army Corps of Engineers, and at Vestal, the bed roughness decreased from 1941 to 1965. Meander bends showed little migration, but tributary mouth bars have showed significant deposition and erosion at different times. Island migration has been more significant than meander bend migration, and islands have both translated and expanded in the upstream and downstream directions. Most notably, two islands, downstream of sites of channel engineering, showed significant deposition during the ten-year period when construction was most intense. The patterns of channel migration did not coincide with record floods. Since 1937, anthropogenic channel alteration has caused more significant channel migration than have large floods. However, migration occurred quickly, and subsided soon after the alterations. |
