Author: Jeffrey A. KirtlandPublisher:
ISBN:
Category : Nooksack River, South Fork (Wash.)
Languages : en
Pages : 0
Book Description
Identifying sources and timing of sediment production and delivery provides information useful to understanding the geomorphology of a forested mountainous watershed in the western Cascade Range of Washington State. Sediment production and delivery is studied by constructing a partial sediment budget for the upper South Fork of the Nooksack River drainage (South Fork drainage). The period of the partial sediment budget extends from 1940 through 1991 and encompasses the pre- and post-management history of the watershed. Four major sediment production and delivery sources - landsliding, streambank erosion, sheet and rill erosion and road-related erosion - were identified in the South Fork drainage. Each source was quantified in the field (1993) to determine its contribution to the volume of sediment produced and delivered to stream channels. The field data were coupled with data obtained from aerial photographs flown in 1940, 1956, 1972, 1979, and 1991 to yield a history of the basin and an estimate of the total sediment production and delivery for the entire study area over 52 years. I document the sediment delivery rate over the 52 years study period to be 110 m3 km-2 yr-1 or 200 metric tons km-2 yr-1 This sediment production rate, which is comparatively less than sediment production rates measured elsewhere in the Pacific Northwest (Kelsey, 1980; Lehre, 1982; Raines, 1991), is attributed to a relatively stable geologic substrate and a lack of a recent massive landslide or major flood event in the South Fork drainage. This does not imply that these large events do not occur; nearly one tenth the land area is underlain by landslide-mobilized material, but that these events have not occurred during the study period.