Effects of Fine Sediment Intrusion on Spawning Gravel in Southeast Alaska

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by Jeffrey B. Bradley, WEST Consultants, Carlsbad, United States,
Dudley W. Reiser, WEST Consultants, Carlsbad, United States,

Document Type: Proceeding Paper

Part of: Hydraulic Engineering:

Abstract: The supply of sediment to forest streams in Southeastern Alaska is related to the inherent instabilities of landforms, stream channels and the effects of logging practices. Debris avalanches, flows and slides supply a large proportion of sediment to first order streams in steep terrain at the upper portion of watersheds. In lower reaches with relatively mild terrain, sediment inputs occur mainly as a result of streambank erosion and from routing of sediment from upstream reaches. Sediment supply and transport in forest streams can be accelerated above natural levels by timber harvesting and road building activities. There is a perception, without adequate data collection and evaluation to support it, that timber harvest activities in the Tongass National Forest of southeast Alaska have significantly increased sediment introduction to stream channels subsequently harming the anadromous and resident fishery. The primary purpose of this investigation was to identify the effects of fine sediment intrusion on salmon habitat, and to develop a detailed data collection program for the Tongass National Forest.

Subject Headings: Sediment | Forests | Gravels | Stream channels | Rivers and streams | Sediment transport | Streamflow | Water flow | Terrain | North America | Alaska | United States

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