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Date Permissions Signed

5-21-2018

Date of Award

Winter 1991

Document Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Kelsey, H. M.

Second Advisor

Easterbrook, Don J., 1935-

Third Advisor

Burmester, Russell F.

Abstract

A sediment budget constructed for the Grouse Creek basin in northern California provides information on the sources and timing of sediment production to aid land managers in understanding the effects of logging impacts in a sensitive watershed. The sediment budget yields a sediment production rate of 1,750 t/km2/yr for a 29-year period. This rate is among the highest for such disturbed forested basins in the Pacific Northwest. Approximately 40 percent of the Grouse Creek basin, which is bisected by regional structural features that have created zones of weak and altered rock, has been logged in the last 35 years.

Sediment production is dominated by mass wasting and is concentrated in areas of geologic instability and logging and during major storms. Over 86 percent of all sediment was produced by landsliding, with 71 percent of landslide volumes generated during a six-year period that includes the flood of December 1964. Ninety-three percent of all sediment volumes were generated during the 15-year period from 1960 to 1975 that included four major storm events, the completion of 74 percent of basin logging activity and 80 percent of road building. Landsliding in old growth was found to be spatially related to erosion in managed areas. Sediment produced in logged and roaded areas increased the frequency of streamside landsliding in some downstream, unmanaged areas by channel aggradation and lateral corrosion of the streambanks.

The remainder of sediment produced from erosion of streambanks, bare hillslopes, and roads is less than 14 percent of the total sediment production. However, as landsliding decreased after 1975, the relative importance of hillslope erosion and road-related erosion increased. Erosion rates from roads are 20 to 140 times the erosion rates in the unmanaged areas and 7 to 34 times those in logged areas.

Erosion processes in Grouse Creek were found to differ by stream order. Debris torrents and streambank erosion dominate in second and third-order channels, whereas streamside landsliding was more frequent in fourth through sixth-order streams. An estimate of the increase in stored sediment indicates 27 percent of the sediment introduced to stream channels during the 29-year period of the study is still in the system.

Type

Text

Keywords

Sediment budget, Sediment production, Landslinding

Publisher

Western Washington University

OCLC Number

1084745523

Subject – LCSH

Erosion--California--Humboldt County; Sediment transport--California--Humboldt County

Geographic Coverage

Humboldt County (Calif.); Grouse Creek Watershed (Calif.)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this thesis in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

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Geology Commons

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