Author(s): Timothy J. Randle; Robert C. Hilldale; Jeffrey D. G. Marr; Sara R. Johnson
Linked Author(s):
Keywords: No Keywords
Abstract: The U. S. Department of the Interior plans to remove Elwha and Glines Canyon Dams on the Elwha River, near Port Angeles, Washington, U. S. A. to restore the ecosystem and native anadromous fisheries. By 2012, when dam removal may begin, the two reservoirs are predicted to contain 16 million m3 of sediment from the 840 km2watershed. This will be the largest volume of reservoir sediment erosion associated with dam removal in North America and, therefore, offers a unique learning opportunity. The Bureau of Reclamation, in cooperation with the National Park Service, is currently installing a series of bedload impact sensors to continuously monitor the bedload movement following dam removal. The use of a surrogate method of sediment transport measurement is an attempt to supplement classic physical sampling of bedload. The surrogate methods to be used on the Elwha River are a result of research performed jointly by the Bureau of Reclamation and the National Center for Earth-Surface Dynamics (St. Anthony Falls Laboratory, University of Minnesota), funded by the Federal Interagency Sedimentation Project (FISP). This research builds on similar bedload measurement developments in the U. S. A, Norway and Switzerland. Three different sensor types will be used, including geophones, accelerometers and hydrophones. The geophones and accelerometers will be attached to the underside of steel plates, mounted to a steel structure that spans the channel width of 38 m. The steel structure contains a series of 73 steel plates, acoustically isolated from each other and mounted on the downstream side of a concrete weir. Hydrophones will be employed outside of the steel structure. Installation of the three sensors and steel structure will be completed by fall 2009. Following installation, a field calibration of the sensors will take place. This site will be ideal to test other surrogate bedload measurement methods due to the reliability of coarse sediment being transported past this site.
Year: 2009