Quantifying impacts to riparian wetlands associated with reduced flows along the Greybull River, Wyoming
- 107 Downloads
Reductions in river flows associated with hydrologic changes from diversions may reduce water elevations and impact hydrology of riparian wetlands. The U.S. Army Corps of Engineers and other federal agencies currently do not have appropriate tools to evaluate effects of hydrologic changes on wetlands. We describe use of HEC-RAS modeling to predict and quantify wetland impacts along 10 km of the Greybull River, Wyoming, USA following a proposed 28,313 L/sec diversion for a new off-channel reservoir. Riparian wetlands were delineated and mapped on aerial photographs and topographic maps. A water-surface-profile model of the river was developed using the HEC-RAS model. Floodplain boundaries with and without the diversion were plotted to the same scale and overlaid on the wetland maps to estimate area of wetlands that would not be flooded under the reduced flow model. The model predicted that total area flooded under the 28,313 L/sec diversion in the reach analyzed would be reduced from 167.2 to 149.7 ha and that approximately 0.47 ha of wetland would be impacted by the diversion. We believe that the procedure we used is a valid method to quantify effects of diversion on riparian wetlands and that this procedure should be further evaluated as a method to assess wetland impacts on similar projects.
Key WordsGreybull River HEC-RAS modeling riparian wetlands Wyoming
Unable to display preview. Download preview PDF.
- Chow, V. T. 1959. Open Channel Hydraulies. McGraw-Hill, New York, NY, USA.Google Scholar
- Henderson, F. M. 1966. Open Channel Flow. The McMillan Company, New York, NY, USA.Google Scholar
- Lewallen, N.J. 1994. Conveyance loss modeling of two Wyoming rivers. M.S. Thesis. University of Wyoming. Laranne, WY, USA.Google Scholar
- Linsley, R. K., M. A. Kobler, and J. L. H. Paulhus. 1975. Hydrology for Engineers. 2nd Edition. McGraw-Hill, Inc., New York, NY, USA.Google Scholar
- Martner, B. E. 1986. Wyoming Climate Atlas. Wyoming Water Research Center, University of Wyoming. University of Nebraska Press, Lincoln, NE, USA.Google Scholar
- Shoemaker, T. G., S. L. Ellis, and H. W. Shen. 1981. Development of minimum streamflow recommendations for maintenance of whooping crane habitat on the Niobrara River, Nebraska, p. 155–174.In J. C. Lewis (ed.), Proceedings of the 1981 Crane Workshop. National Audubon Society, Tavernier, FL, USA.Google Scholar
- U.S. Army Corps of Engineers. 1987. Corps of Engineers Wetlands Delineation Manual. Waterways Experiment Station. Vicksburg, MS, USA. Technical Report Y-87-1.Google Scholar
- U.S. Army Corps of Engineers 1992. HEC-FFA Flood Frequency Analysis Users Manual. Hydrologic Engineering Center, Davis, CA, USA.Google Scholar
- U.S. Army Corps of Engineers. 1995. HEC-RAS River Analysis System User’s Manual. Hydrologic Engineering Center, Davis, CA, USA.Google Scholar
- Zafft, D. J. and T. C. Annear. 1992. Assessment of stream fishery impacts and instream flow recommendations related to the Greybull Valley Project. Wyoming Game and Fish Department, Cheyennc, WY, USA. Administrative Report IF-2292-0909001.Google Scholar