Document Type
Thesis
Date of Degree Completion
Fall 2024
Degree Name
Master of Science (MS)
Department
Cultural and Environmental Resource Management
Committee Chair
Dr. Clay Arango
Second Committee Member
Dr. Jennifer Lipton
Third Committee Member
Dr. Alison Scoville
Abstract
Throughout American history, large wood (LW) has been removed from streams to make it easier to transport goods or distribute water. This institutional removal of LW caused bank erosion, channel incision, and a loss of complex in-stream habitat. In the 1970s resource managers realized the benefits of LW in riverine ecosystems, and LW addition has become a widely used restoration technique since. LW addition reverses habitat degradation by increasing macroinvertebrate habitat, accelerating vegetation establishment along stream banks, and slowing swift-moving water which provides refuge for cold water fish while decreasing erosion through sediment retention. While LW habitat benefits are widely accepted, they are monitored infrequently because it is time-intensive and not a funding priority. However, the advent of free statistical analysis programs, modeling software and aerial imagery is making monitoring cost-effective and less resource intensive. To showcase alternate methods of habitat restoration monitoring, I studied stream habitat change after LW addition to 6 low order streams in the Upper Yakima River watershed, and I developed a Normalized Difference Vegetation Index (NDVI) analysis in GIS to analyze habitat change in a stream approximately 10 years after LW restoration. I also used the Army Corps of Engineers Hydrologic Engineering Center’s River Analysis System (HEC-RAS) modeling tool to explore interactions between LW and flood stage and to forecast habitat change after wood addition. In the before-after study, I found that LW increased stream pool width and length but decreased depth and pool tail crest depth. The NDVI analysis showed high levels of vegetation loss around LW jams that had been moved into place by a large flood, which suggested that LW can strongly influence channel geomorphological and riparian zone changes when activated and moved by large floods. The HEC-RAS model showed that floodplain inundation depends more on the size of the flood than on different LW loading scenarios. This tool can be used to optimize wood addition placement or amount. Resource managers can use the methods and techniques I developed to better understand, quantitatively, the effects LW has on stream systems to bring about positive habitat change.
Recommended Citation
Hill, Kyle, "Monitoring the Effects of Large Wood Additions to Streams: A Spatially Scaled Approach to Understanding Stream Habitat Restoration Benefits" (2024). All Master's Theses. 1990.
https://digitalcommons.cwu.edu/etd/1990