Skip to Main Content
Quaternary geology and geomorphology of the lower Deschutes River Canyon, Oregon.Author(s): Jim E. O'Connor; Janet H. Curran; Robin A. Beebee; Gordon E. Grant; Andrei Sarna-Wojcicki
Source: Oregon Water Science and Application. 7: 77-98
Publication Series: Scientific Journal (JRNL)
PDF: Download Publication (3.77 MB)
DescriptionThe morphology of the Deschutes River canyon downstream of the Pelton-Round Butte dam complex is the product of the regional geologic history, the composition of the geologic units that compose the valley walls, and Quaternary processes and events. Geologic units within the valley walls and regional deformation patterns control overall valley morphology. Valley bottom morphology is mostly the result of Quaternary events. These include several large landslides, which have caused retreat of the canyon rims but have also constricted the valley bottom with immense volumes of debris. In at least two instances (as at Whitehorse Rapids), landslides blocked the channel, resulting in ponding, breaching of landslide dams, and downstream floods. Large floods from other mechanisms have also formed many valley-bottom features along the lower Deschutes River. A large Pleistocene lahar resulting from a circa 0.07 Ma eruption of Mount Jefferson left bouldery deposits along the valley margins for most of the canyon length. The 15,000-12,700 14C yr BP Missoula floods backflooded up the Deschutes River from the Columbia River and mantled the downstreammost 60 km of Deschutes River valley with bedded silt and clay. A large, possibly meteorologic flood between 6,500 and 3,000 14C yr BP left abundant boulder bars and high sand and silt deposits that flank the channel in wider valley-bottom locations. In contrast, large historic main-stem floods, such as December 1964 and February 1996, had few effects on channel geomorphology due to the volume and coarseness of valley bottom deposits left by the earlier and larger floods and landslides.
- Visit PNW's Publication Request Page to request a hard copy of this publication.
- We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
- This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
CitationO''Connor, Jim E.; Curran, Janet H.; Beebee, Robin A.; Grant, Gordon E.; Sarna-Wojcicki, Andrei. 2003. Quaternary geology and geomorphology of the lower Deschutes River Canyon, Oregon. Oregon Water Science and Application. 7: 77-98
- Geology and geomorphology of the Lower Deschutes River Canyon, Oregon.
- Plugs or flood-makers? The unstable landslide dams of eastern Oregon
- Unusual holocene alluvial record from Rio Del Osos, Jemez Mountains, New Mexico: Paleoclimatic and archaeologic significance
XML: View XML