1 Preliminary Assessment of Sediment Transport Dynamics Following Dam Removal: A Case Study

Prediction of sediment transport dynamics following dam removal usually requires extensive field data, the collection of which requires both resources and time. Certain management decisions regarding dam removal, however, may be required before resources may be allocated to provide sufficient data to evaluate whether dam removal is a viable option. Here, we present a case study and demonstrate that some aspects of the sediment transport characteristics following dam removal can be evaluated with very limited information. The case study in question involves J.C. Boyle, Copco, and Iron Gate Dams on the Klamath River, California which together have an estimated 12 million m3 of sediment deposited in their reservoirs. With a reconnaissance field observation and upon examination of the very limited existing field data, we determined that it is possible to evaluate the potential for sediment deposition downstream of the dam following the removal of the dams under the worst-case-scenario assumptions. The evaluation was carried out with the help of DREAM-1, one of the Dam Removal Express Assessment Models developed at Stillwater Sciences. Results of the assessment indicate that potential sediment deposition would occur only for a brief period within approximately 10 km downstream of the dam with a maximum thickness of sediment deposition no more than 1.2 m