Tuesday, June 5, 2007
541

Can we restore stream ecosystem structure in urban catchments? Potential recovery through stream restoration

Peter A. Cada1, Elizabeth B. Sudduth2, Brooke A. Hassett3, and Emily S. Bernhardt3. (1) Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708, (2) University Program in Ecology, Duke University, Durham, NC 27708, (3) Department of Biology, Duke University, Durham, NC 27708

We documented reach scale changes in the physical structure of 12 stream channels, comparing four small streams draining forested catchments with eight streams from developed watersheds of similar area.  Study sites in four of the urban streams are within recently implemented natural channel design restoration projects.  By comparing reach-scale geomorphic (e.g. slope, cross section, % incision, variation in water depth) and hydrologic (e.g. transient storage volume, surface-water groundwater exchange, fine scale variation in velocity) features of each stream we assessed if restoration projects increased stream heterogeneity and in-channel residence time relative to degraded conditions.  We used ArcGIS to compile watershed maps as well as to produce detailed maps of reach habitats for each stream. OTIS-P was used to estimate transient storage from field rhodamine releases.  Forested reaches were found to have greater longitudinal slope, shallower average depths, and greater variation in depth than urban or restored stream reaches. Urban streams had less variation in flow habitats and lower transient storage volume than forested streams, while streams restored to provide habitat had the lowest flow habitat heterogeneity and transient storage volume of the three stream classes.  Improvements in restoration design are necessary to restore the physical template of less impacted streams.


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