Identification of Unstable Reaches and Stream Channel Design Parameter
Research Foundation of SUNY/Buffalo State College
Basin Program Funds:
In a severely eroding stream there is not sufficient hydrological information to adequately design the appropriate BMPS in the appropriate locations.
Human modification of watersheds has produced profound changes in streams throughout the Great Lakes basin. A growing emphasis on environmental quality has generated concern about the effects of humans on stream ecosystems. One water quality issue that is of particular concern in human-modified streams is sediment pollution, as sediment is the largest pollutant in our waters by volume and mass. Sources of sediment in a stream may include bed and bank erosion, overland erosion, and discharges from anthropogenic activities (e.g., industrial and municipal discharges and combined sewer overflows). The Buffalo River watershed in NY has been severely impacted by human activity and sediment pollution has been a particular problem. Moreover, sediment from upstream bank erosion has been cited as a primary problem in the watershed.
The International Joint Commission (IJC) has designated the Buffalo River as one of 43 Areas of Concern (AOC). The designation was based, in part, on factors like degradation of fish and wildlife habitat and contaminated bed sediment in the river. Early work in the Buffalo River watershed found that soil and bed and bank erosion from the upper watershed has been the primary contributor of sediment to the AOC. Research has estimated that sediment load to the Buffalo River AOC from upstream erosion was 460,000 tons/year, which was 66% and 40% greater than sediment loads from combined sewer overflows and direct industrial discharges, respectively.
Cazenovia Creek is one of three main tributaries to the Buffalo River and the creek has received a high prioritization for the identification of non-point pollution sources to improve water quality based on a report from Erie County Water Quality Coordinating Committee in 2000. Sediment, particularly silt-sized sediment from stream bank erosion from upstream sources, has been cited as the primary impairment in Cazenovia Creek. Bank stabilization has been implemented in Cazenovia Creek in an effort to reduce sediment input from stream bank erosion. Fourteen and one half kilometers of Cazenovia Creek were part of a Natural Resources Conservation District (NRCS; formerly the Soil Conservation District) bank stabilization program that began in 1953. Moreover, the creek has been the target of recent stream bank stabilization projects to address the issue of in-stream sediment sources and there has been considerable interest in using biotechnical bank stabilization to reduce sediment inputs to the watershed.
The overall goal of this project was to collect regional reference data in the Cazenovia Creek watershed for the calculation of stream channel design parameters. This will allow for recommendations to be made about what type of engineering techniques (i.e., soft versus hard) should be used in specific stream reaches. The objectives of the proposed research were threefold:
The first objective provided an improved understanding of factors controlling spatial and temporal variation in channel dynamics at the watershed- and reach-scales in a human-modified stream network. The second objective provided some explanation of the mechanisms of changes in channel morphology and highlight reaches in the watershed that is currently classified as unstable. The third objective allowed for the calculation of stream channel design parameters in order to determine what method of bank stabilization would be most appropriate to reduce sediment input to the stream.
- develop a GIS-based inventory of historical and current stream patterns.
- link the GIS inventory to qualitative notes on stream bank stability collected by Erie County SWCD and NRCS during annual stream reconnaissance surveys to relate changes in stream morphology to mechanisms of channel change.
- perform quantitative stream surveys in reaches that are deemed unstable based on the GIS analysis and stream reconnaissance visits in order to calculate stream channel design parameters for those reaches.
All tasks proposed for this project have been completed, including: 1) aerial photographs of the Cazenovia Creek watershed for the years 1938, 1951, 1958, 1978, 1990, 1995, and 2002 were scanned, georeferenced, and digitized; 2) channel change calculations were made between successive years of photos and the mechanisms of channel change (e.g., lateral migration, channelization, recovery) were documented; 3) target reaches where channel change was noted between the 1995 and 2002 aerial photos were identified and field data on channel form and bed sediment characteristics were collected in these reaches; 4) stability threshold analysis was used to determine what method of bank stabilization would be most appropriate to reduce sediment input to the stream in the target reaches.
We were not able to perform the watershed-scale GIS analysis on the 1942 and 1966 sets of aerial photos because of missing photos. Photos for the downstream section of the creek were also missing from the 1938 photo set. In addition, we were able to survey six of the fourteen target reaches identified as unstable (1995-2002 air photos) because we were not able to obtain landowner permission to gain access to all the reaches.
Contact: Dr. Kelly M.Frothingham, 716-878-6736