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Date Permissions Signed
Date of Award
Master of Science (MS)
Homann, Peter S., 1953-
Bach, Andrew J.
Helfield, James M.
In 2014, dam removal from the Elwha River, Washington state, exposed large areas of previously submerged sediment. The Olympic National Park placed ~100 large logs on 2 ha of exposed sediment to promote plant establishment. I quantified patterns of three microclimate variables near logs: wind speed at 10-cm height (u10), sediment temperature (TS), and evaporation rate (E); and their relationships to broader environmental factors. The northern-most log, exposed to northerly winds, was measured along 3-m perpendicular transects 14 times during August and September 2015. I determined nonlinear and multilevel regressions to investigate patterns and create models of microclimate as functions of environmental factors and distance from the log. Maximum u10 decreased to the lee. Decreases near the log occurred for u10 to the north and south, and for TS and E to the shaded north. Windward and leeward u10 models include local wind speed and distance from log. Northern TS is related to solar radiation, air temperature and distance from log. Southern TS is related to air temperature. Northern E is related to solar radiation, vapor pressure deficit and distance from log. Southern E is related to solar radiation and vapor pressure deficit. Models of southern u10 and northern TS and E were validated with data from 8 wind-protected logs, but lack of validation of the other microclimate models indicate the northern-most log has unique microclimate. Species-specific physiological information is required to predict plant reactions to near-log microclimate. All models require more data to broaden their scope.
woody debris, dam removal, restoration, microclimate, microclimate model, Elwha, dam restoration, windbreak
Western Washington University
Subjects – Names (LCNAF)
Elwha River Watershed (Wash.)--Environmental conditions; Elwha Dam (Wash.)
Subject – LCSH
Restoration ecology--Washington (State)--Elwha River Watershed; Coarse woody debris; Microclimatology; Dam retirement--Washington (State)--Elwha Dam
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.
Colton, Mariah J., "Daytime Summer Microclimate Influence of Large Woody Debris on Dewatered Sediments in Lake Mills, WA Following Dam Removal" (2018). WWU Graduate School Collection. 712.