Stream-channel response to the January 3-5, 1982 storm in the Santa Cruz Mountains, west central California

Abstract

Intense rainfall on January 3-5, 1982 in the Santa Cruz Mountains, California caused high streamflow and widespread landsliding. Generalized channel response in the studied basins included scour in steep, low-order channels and moderate fill in higher order channels. Large volumes of channel fill were noted along some channels but this was limited to reaches that received large volumes of colluvium from debris flows and streamside debris slides. The local nature of these effects on channel geometry contrasts with widespread depositional effects observed following major storms in steep terrain in other parts of California. The morphology of most intermediate and high-order channels in the study area appear to have been formed at least as much by events with moderated recurrence intervals as by extreme events. Along low-order channels that were scoured and along isolated reaches of some intermediate and high-order channels where fill was severe, however, storm effects will probably persist for long periods of time. Since the localized effects of high magnitude storms can persist longer than the recurrence interval of the storms themselves, channel morphology throughout the area probably reflects the effects of a number of storms. (USGS)