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Effects of Stream and Elevation Resolution on Riparian Metrics and Restoration Identification
Citation:
CHRISTENSEN, J. AND D. W. EBERT. Effects of Stream and Elevation Resolution on Riparian Metrics and Restoration Identification. Presented at American Water Resources Association, Seattle, WA, November 09, 2009.
Impact/Purpose:
Presentation materials
Description:
Even though riparian areas attenuate nutrients and sediments from agricultural runoff at the field scale, best management practices and locations for restoring riparian areas should be determined at watershed scales. Riparian metrics (e.g., percent forest within 100m of stream) applied at watershed scales can be related to water quality but fail to account for the spatial location and the flow paths through riparian and contributing sources areas (e.g., agriculture). Additional metrics have been developed using GIS models that incorporate spatial location and flow paths. One utility of spatially-explicit metrics is to identify potential riparian restoration sites. However, the resolution of the stream and elevation data from which these metrics are derived may bias the metrics and hence the identification of potential restoration sites. We compared metrics at different stream and elevation resolutions in a watershed in North Carolina that has high densities of confined animal feedlot operations (CAFOs). Potential riparian restoration sites were selected that would intersect with flowpaths from agricultural fields adjacent to CAFOs. Stream resolutions of 1:100,000 and 1:24,000 and potential flowpaths that would incorporate agricultural ditching were used. Elevation resolutions included 30m, 10m and 6m grids. We found that increases in stream resolution resulted in a decrease in the extent of buffered agriculture and an increase in agriculture-to-buffer ratios, which then altered the identification of restoration sites. These patterns were most prominent when agricultural drainage was included. The extent of buffered areas decreased slightly with increasing elevation resolution but had minimal effects on restoration selection. More pronounced effects might be seen in areas of less relief. This study demonstrated the importance of including constructed extensions to stream networks (e.g., ditching and tiling) when considering the relationship of the stream network, riparian areas, and agricultural lands. Spatial data about ditches and tiles are currently limited and therefore the extent and location of such hydrologic modifications should be estimated and predicted in order to produce improved riparian metrics and restoration plans. Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.
URLs/Downloads:
CHRISTENSEN 09-056 AWRA ABSTRACT 2009 V3.PDF (PDF, NA pp, 8 KB, about PDF)CHRISTENSEN 09-056 SLIDE AWRANOV09PRES.PDF (PDF, NA pp, 4483 KB, about PDF)