Fluvial geomorphology of a boulder-bed, debris-flow - Dominated channel in an active tectonic environment

摘要

Numerous streams, with a drainage area of a few square kilometers, draining the south flank of the Santa Ynez Range in Southern California are characterized by steep boulder-bed, debris-flow-dominated channels. Rattlesnake Creek is a good example. Approximately 90% of the stored sediment in the stream valley is stable debris flow deposits found in debris flow terraces and levees adjacent to the channel. The remaining 10% of stored sediment resides in the active channel, where the channel morphology is dominated by large boulders (1 to 4+m in diameter) derived from debris flows or rock fall that, along with bedrock outcrops, form rock or boulder transverse ribs with frequent step-pools.