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Date Permissions Signed

5-15-2018

Date of Award

Summer 1988

Document Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Kelsey, H. M.

Second Advisor

Suczek, Christopher A., 1942-2014

Third Advisor

Lacher, Thomas E.

Abstract

The bedload of a gravel-bed stream was sampled from two reaches, one upstream and one downstream of a large (1.0x106 m3 of material removed) landslide, in order to assess the change in particle-size distribution caused by the influx of the finer-grained landslide material. For sampling purposes, the bedload was initially stratified on the basis of apparent grain size variability into 11 strata, or channel map units. Surface and subsurface materials were sampled independently. Subsurface sample sites were selected using stratified random sampling, with 30 sites upstream and 36 downstream of the landslide. Sampling techniques were modified from Church et al. (1987) for the subsurface material and were based on weight proportion. Surface material was sampled using Wolman's (1954) pebble-count method. Thus subsurface statistics were based on weight proportion, while surface analysis was based on number of particles. The two reaches were compared using the same pairwise comparison for both the surface and subsurface material. Subsurface material differs significantly between upstream and downstream reaches (finer downstream) in all but the finest and largest grain-size classes. Surface distributions also differ significantly between upstream and downstream (also finer downstream). Surface material was compared to subsurface material by calculating the ratio of surface graphic mean (Folk, 1980) to subsurface graphic mean for the identical range of grain sizes. This technique assumes statistical equivalence between sieve-by-weight (subsurface) and grid-by-number (surface) techniques of data collection. Ratios of surface graphic mean to subsurface graphic mean for the channel map units ranged from 1.0 to 6.0, with only one channel unit having a ratio of less than 2. Surface to subsurface graphic mean ratios greater than 2 indicate different grain-size populations. Because of different grain-size populations, the dominant mechanism of surface coarsening in the Deer Creek channel is probably equal mobility of all grain sizes during transport rather than winnowing of finer grain sizes.

Type

Text

Keywords

Gravel-bed streams, Gravel distribution, Stream sediment

Publisher

Western Washington University

OCLC Number

1079910127

Subject – LCSH

Sediment transport--Washington (State)--Deer Creek Watershed; Bed load--Washington (State)--Deer Creek Watershed; River channels--Washington (State)--Deer Creek

Geographic Coverage

Deer Creek Watershed (Wash.); Deer Creek (Wash.)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document 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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