Date of Award:

5-2014

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Committee Chair(s)

Patrick Belmont

Committee

Patrick Belmont

Committee

Nicolaas Bouwes

Committee

Tammy Rittenour

Abstract

Historically the Columbia River was amongst the most productive salmonidbearing watersheds in North America. Currently, salmonid populations have collapsed and are estimated at ten percent of historic levels. Because of this, there are thirteen, Endangered Species Act (ESA) listed distinct population segments within the Columbia River Basin (CRB). The Bonneville Power Administration (BPA) operates a substantial number of hydroelectric dams within the CRB. As the dams effectively block anadromy and are thought to be extremely detrimental to the long-term persistence of salmonid populations within the CRB, the BPA funds a series of programs to mitigate the impacts of dam operation. One such program is the National Oceanographic and Atmospheric Administration’s (NOAA) Integrated Status and Effectiveness Monitoring Program (ISEMP). ISEMP’s goal is to develop and test strategies for determining the status and trend of salmonid populations and their habitat in the CRB. In 2010 ISEMP started the Columbia Habitat Monitoring Program (CHaMP) to initiate and implement a standardized approach to salmonid monitoring within the CRB. ISEMP and CHaMP are partial funders of this thesis study and desired watershed-level geomorphic context for their restoration and monitoring efforts within the CRB. Specifically this project consisted of a first-order examination of the following broad research questions: 1) How do long-term rates of sediment supply vary spatially and temporally throughout the Columbia River Basin (CRB)? 2) How have human activities influenced (amplified or dampened) processes of erosion and sediment transport? 3) At what scales do long-term and near-term rates of sediment yield influence aquatic habitat metrics?

I addressed these questions at multiple spatial and temporal scales within the CRB primarily using cosmogenically derived catchment-averaged millennial-scale erosion rates. The principal findings were:

  • There is an order of magnitude variability in long-term sediment yield at the scale of the entire CRB.
  • This spatial variability is generally poorly predicted from simple topographic and environmental parameters. A notable exception is a strong positive correlation between long-term sediment yield and mean annual precipitation.
  • Where functional relationships exist between topographic and environmental parameters and sediment yield the nature of those relationships is scale and situation dependent.
  • Within Bridge Creek, John Day Watershed, Oregon I showed how CAER can be coupled with C14 or OSL dates and stratigraphic analysis to understand timing and duration of channel cut and fill cycles.
  • Within the Cascade Range in Washington I illustrated how the geomorphic history of a watershed (e.g., glaciation) can have a profound influence on modern sediment dynamics.
  • CAER can be used to effectively quantify changes in sediment supply at the watershed level if those changes are drastic (e.g., transition from glacial dominated to fluvial dominated erosion) but appears to be too coarse in the absence of near-term rates (i.e., yearly to decadal sediment yield) to effectively quantify the temporary pulse of sediment associated with wild-fire (e.g., Tower fire, EBNFC, JDW) if the scale of disturbance isn’t sufficiently large.
  • I identified a positive correlation in the Cascades, WA between long-term sediment yield and potentially alluvial reaches.

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