Collaborative NSF Research on Effects of Dam Removal Begun

Richard Cahill, representing the Illinois State Geological Survey, and Shane Csiki and Bruce Rhoads, from the Department of Geography, University of Illinois, are investigating the potential impact of dam removal on stream systems. This project started in 2008 and is being funded by the National Science Foundation (NSF). Many dams are deteriorating, and funds are no longer available for maintenance. This situation is particularly true for dams that do not create impoundments exceeding the bankfull stage (channel capacity) of a river channel during normal flow conditions. It is important to understand how these dams influence stream morphology and sediment storage in order to better predict how future removals may affect streams.

The project goal is to explore how run-of-river dams affect stream morphology and sediment storage. The study focuses on four run-of-river dams in the Till Plains Section of the Central Lowland Physiographic Province within Illinois. Specific objectives are (1) to assess the impact of run-of-river dams on the river channel above and below each dam, (2) to assess similarities and differences of these impacts among the set of dams, and (3) to compare the effects caused by run-of-river dams to those caused by impoundment dams.

The research will be conducted in four phases. In the first phase, hydrologic information will be collected from nearby gauging stations, and the watershed area above each dam will be calculated. In the second phase, data on channel bathymetry and sediment characteristics will be collected upstream and downstream of each dam. The degree of sedimentation above the dam will be determined through coring. The third phase involves particle size analysis of the collected sediment and bed samples, cesium-137 (137Cs) analysis of cores for determination of sediment deposition rate, calculation of the above-dam sediment characteristics using Geographic Information Systems (GIS) for mapping of the stored sediment, and quantitative analysis of spatial patterns. The fourth phase involves comparisons among the data to evaluate conditions across the dams being studied in this project and to compare this study's findings with findings for impoundment dams. It is in this final phase that the data from the stream gauging stations and dam operational histories will be used to help explain the effects these dams have caused on streams.