Recovery of aggraded stream channels at gauging stations in northern California and southern Oregon

Abstract

Abstract - Discharge measurements at nine gauging stations in northern California and southern Oregon document episodes of channel bed aggradation lasting 5 to 15 years after the flood of December 1964 to January 1965. Bed elevations rose 1 to 4 m, then gradually declined to a stable level at or above the pre-flood level. Seven gauging sections widened by 7 to 105 per cent during the aggradation episodes. Channels formed within aggraded material narrowed during degradation; in one case, the pre-flood width was attained. Eroded streambanks formed in non-alluvial material rarely advanced because of 1) post-1964 flood flows, 2) the slowness of processes forming non-alluvial streambanks, and 3) the difficulty of establishing riparian vegetation under the conditions of coarse substrate and seasonal rainfall. These results suggest that infrequent large floods are more effective in shaping stream channels in highly erosive terrane with seasonal rainfall than in less erosive humid areas with comparable amounts of annual precipitation.

Citation

Lisle, T. E. 1981. Recovery of aggraded stream channels at gauging stations in northern California and southern Oregon. In: Timothy R. H. Davies and Andrew J. Pearce (eds.), Erosion and Sediment Transport in Pacific Rim Steeplands, Proceedings of the Christchurch Symposium, 25-31 January 1981, Christchurch, New Zealand. Int. Assn. Hydrol. Sci. Pub. No. 132: 189-211.