Open File Report 2014–1114
Prepared in cooperation with the U.S. Army Corps of Engineers
Assessment of Suspended-Sediment Transport, Bedload, and Dissolved Oxygen during a Short-Term Drawdown of Fall Creek Lake, Oregon, Winter 2012–13
By Liam N. Schenk and Heather M. Bragg
- The drawdown of Fall Creek Lake resulted in the net transport of approximately 50,300 tons of sediment from the lake during a 6-day drawdown operation, based on computed daily values of suspended-sediment load downstream of Fall Creek Dam and the two main tributaries to Fall Creek Lake.
- A suspended-sediment budget calculated for 72 days of the study period indicates that as a result of drawdown operations, there was approximately 16,300 tons of sediment deposition within the reaches of Fall Creek and the Middle Fork Willamette River between Fall Creek Dam and the streamgage on the Middle Fork Willamette River at Jasper, Oregon.
- Bedload samples collected at the station downstream of Fall Creek Dam during the drawdown were primarily composed of medium to fine sands and accounted for an average of 11 percent of the total instantaneous sediment load (also termed sediment discharge) during sample collection.
- Monitoring of dissolved oxygen at the station downstream of Fall Creek Dam showed an initial decrease in dissolved oxygen concurrent with the sediment release over the span of 5 hours, though the extent of dissolved oxygen depletion is unknown because of extreme and
rapid fouling of the probe by the large amount of sediment in transport. Dissolved oxygen returned to background levels downstream of Fall Creek Dam on December 18, 2012, approximately 1 day after the end of the drawdown operation.
First posted August 7, 2014
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Schenk, L.N., and Bragg, H.M., 2014, Assessment of suspended-sediment transport, bedload, and dissolved oxygen during a short-term drawdown of Fall Creek Lake, Oregon, winter 2012–13: U.S. Geological Survey Open-File Report 2014–1114, 80 p., https://dx.doi.org/10.3133/ofr20141114.
ISSN 2331-1258 (online)
Data Collection and Methods
Suspended- Sediment Budgets
Bedload below Fall Creek Dam
Summary and Conclusions
Appendix A—Monitoring Station Analyses and Sediment Model Descriptions