How the River Runs: Measuring stream fragmentation in urban and non-urban watersheds

Authors: Mary O'Brien, Eastern Washington University, Erin Dascher*, Eastern Washington University
Topics: Water Resources and Hydrology, Human-Environment Geography, Anthropocene
Keywords: Spokane River Basin, River Fragmentation, Connectivity, GIS
Session Type: Virtual Paper
Day: 4/8/2021
Start / End Time: 8:00 AM / 9:15 AM
Room: Virtual 3
Presentation File: No File Uploaded


This research examines how urbanization causes unique patterns of fragmentation in four sub-watersheds within four watersheds of the Spokane River Basin. Dams, culverts, and road crossings are anthropogenic barriers that fragment rivers and alter their geomorphic and biologic properties. Urbanization increases river fragmentation by increasing the density of instream barriers, stream burial, sewage and stormwater piping. Fragmentation of river systems disrupts fish migration, alters sediment and flow regimes, and complex ecosystems in riparian zones. A dataset of instream barriers was compiled using data from the Washington Department of Fish and Wildlife Fish Passage Inventory, StreamNet, the Idaho Department of Fish and Game, the National Hydrography Dataset (NHD), and an investigation of aerial imagery. Once compiled the instream barrier dataset was used in conjunction with the NHD High Resolution flowlines to create models of connectivity using the Barrier Assessment Tool (BAT), an ArcGIS plugin developed by The Nature Conservancy. To assess the effects of urbanization on river connectivity, models were created for HUC 12 watersheds within the study area that were defined as urban, agricultural, or natural watersheds based on their percentage of land cover and use (LCLU). LCLU data was provided by the National Landcover Dataset. Results demonstrate increased fragmentation in urban watersheds compared to other watersheds. Further, unique patterns of stream fragmentation were apparent in watersheds classified as urban, agricultural, and natural.

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