Declining sediment loads from Redwood Creek and the Klamath River, north coastal California
This article is part of a larger document. View the larger document here.Abstract
River basin sediment loads are affected by several factors, with flood magnitude and watershed erosional stability playing dominant and dynamic roles. Long-term average sediment loads for northern California river basins have been computed by several researchers by several methods. However, characterizing the dynamic nature of climate and watershed stability requires computation of annual loads. We computed annual suspended and bedload loads for the 1950s through 2009 for both Redwood Creek and the Klamath River. Results show high sediment loads coincident with a period of widespread logging by destructive practices and large storms in the 1950s through 1970s followed by a dramatic decline in sediment loads through the present. Analyses of annual departures from mean and time trend tests indicated the decline in loads is not due solely to the lack of very large storms. We infer it can also be explained by the partial recovery of watershed erosional stability from the 1980s through the present due to reduced logging rate, use of lower impact logging practices, and implementation of treatment programs for reducing erosional threats from logging roads.