|Nagle, Gregory - CORNELL UNIV.|
|Fahey, Timothy - CORNELL UNIV.|
Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 7, 2006
Publication Date: N/A
Interpretive Summary: Current problems with excessive sedimentation in Cayuga Lake, New York are a concern for the degradation of the extensive wetlands associated with the lake. Most of the other Finger Lakes have relatively more intact wetland complexes at their southern ends, which filter out sediment from tributaries. Current problems of extensive bank erosion and sediment delivery in the southern basin of Cayuga Lake will be very difficult to correct since they are the result of land use impacts from long ago. In places where sheet erosion are dominant, there are several practical solutions readily available such as different changes in cultivation practices or land use to reduce soil erosion or vegetated buffer strips below fields to capture sediment before it reaches the stream. However, channel and bank erosion will be difficult to effectively control at a reasonable cost. Channel reconstruction and bank revetments are possible, but these approaches are expensive and not always effective. A few channels have been treated with these management practices but extensive areas impacted by channel and bank erosion remain to be treated to protect the wetlands associated with Cayuga and the other Finger Lakes.
Technical Abstract: The goal of this study was to quantify the proportional contributions of stream bank and upland erosion to fine sediment loads in watersheds in central New York. We utilized a simple method of quantifying the sources of fluvial sediment by comparing concentrations of the bomb-derived radionuclide Cs-137 in fluvial sediment with sediment from potential source areas such as agricultural soils, forests, and stream banks. We wanted also to examine whether eroding glacial drift, and in particular glaciolacustrine deposits, could explain the variations in the proportional contributions of bank erosion and upland erosion. The watersheds studied most intensively included five tributaries in the southern Cayuga Lake Basin in the Finger Lakes region of New York, four of which had available data indicating large areas of stream side glaciolacustrine deposits. To compare sediment sources in other areas lacking such extensive stream side areas of fine-grained glacial deposits, samples were taken from ten other watersheds in the Finger Lakes and western Catskills regions. The mean contribution of bank erosion to sediment loads in the five southern Cayuga watersheds averaged 69% (range was 60 to 82%). Although the proportion of bank erosion was also important in several streams from other watershed lacking extensive glaciolacustrine deposits it was less important in most of them with contributions ranging from 0 to 61%.