To improve our understanding of dam effects, we examined the downstream effects of a dam complex on the Deschutes River in central Oregon. We found that the Deschutes is a remarkably stable river due to its geologic and hydrologic setting. Because of this intrinsic stability, the dams that we studied have had virtually no detectable effects on the physical structure of the downstream channel. In spite of this stability, the Deschutes has experienced gargantuan and previously unrecorded floods in the past 100,000 years or so due to large landslides from the canyon walls that temporarily dammed the river. Related fisheries work is showing that the islands and surrounding back channels created by these extremely large and rare floods provide core habitats for diverse fish populations. 

These findings are being directly incorporated into the license renewal application for the Pelton-Round Butte dam and improving our abilities to predict effects of other dams. The research was conducted as a multi-agency partnership between the USFS-PNW Research Station, U.S. Geological Survey, Oregon State University and Portland General Electric.

Published in 2003, "A Peculiar River: Geology, Geomorphology, and Hydrology of the Deschutes River, Oregon" (O'Connor & Grant, eds.) brings together the compelling stories of the river's natural history, in the context of the results of the nine studies conducted as part of the relicensing process. [informational flyer] [buy it here]

Grant, G.E., Schmidt, J.C. and Lewis, S.L. 2003. A Geological Framework for Interpreting Downstream Effects of Dams on Rivers. in J.E. O'Connor and G.E. Grant eds. A Peculiar River. Water Science and Application 7. American Geophysical Union, p203-219.

O'Connor, J.E., Curran, J.H., Beebee, R.A., Grant, G.E. and Sarna-Wojcicki, A. 2003. Quaternary Geology and Geomorphology of the Lower Deschutes River Canyon, Oregon. in J.E. O'Connor and G.E. Grant eds. A Peculiar River. Water Science and Application 7. American Geophysical Union, p73-94.

O'Connor, J.E., Grant, G.E. and Haluska, T.L. 2003. Overview of Geology, Hydrology, Geomorphology, and Sediment Budget of the Deschutes River Basin, Oregon. in J.E. O'Connor and G.E. Grant eds. A Peculiar River. Water Science and Application 7. American Geophysical Union, p7-30.

Fassnacht, H., McClure, E.M., Grant, G.E. and Klingeman, P.C. 2003. Downstream Effects of the Pelton-Round Butte Hydroelectric Project on Bedload Transport, Channel Morphology and Channel-Bed Texture, Lower Deschutes River, Oregon. in J.E. O'Connor and G.E. Grant eds. A Peculiar River. Water Science and Application 7. American Geophysical Union, p169-202.

Grant, G. E., Fassnacht, H., McClure, E., and Klingeman, P., 1999, Downstream effects of the Pelton Round Bute on bedload transport, channel morphology, and channel bed texture.  Final report to PGE

O’Connor, J.,  Grant, G.E., Currans, J.,and Fassnacht, H., 1999, Geomorphology of the Deschutes River below the Pelton Round Butte Dam Complex. Final report to PGE

McClure, E.M., Grant, G.E., Jones, J.A., 1997, Longitudinal patterns of bed material size following impoundment of the lower Deschutes River, Oregon [abs]: Abstracts with Programs - Geological Society of America, v. 29, n. 6, p. 314