Title: Influence of mapping resolution on assessments of stream and streamside conditions: lessons from coastal Oregon, USA
Author: Vance-Borland, Ken; Burnett, Kelly; Clarke, Sharon;
Source: Aquatic Conservation: Marine and Freshwater Ecosystems. 19: 252-263
Publication Series: Scientific Journal (JRNL)
Description: 1. Digital hydrographic data are commonly employed in research, planning, and monitoring for freshwater conservation, but hydrographic data sets differ in spatial resolution and accuracy of spatial representation, possibly leading to inaccurate conclusions or unsuitable policies for streams and streamside areas.
2. To examine and illustrate the potential for different hydrographic data sets to influence in-channel and streamside characterizations, a study area in the U.S. Pacific Northwest was chosen because 1:100 000, 1:24 000, and densified 1:24 000 hydrography are available and widely used in research and management for several species of Pacific salmon and trout at risk. The potential was examined for differences among the digital hydrographic data sets in: (1) spatial extent to influence estimated abundances of fish habitat, streamside buffer conditions, and fish distributions; and (2) spatial position to influence estimated streamside buffer conditions and estimated stream gradient.
3. The analysis of spatial extent found the total stream length represented by the 1: 100 000 hydrography was approximately one-half that of 1:24 000 hydrography and only one-fifth that of densified 1:24 000 hydrography. The 1:100 000 and 1:24 000 networks differed significantly for 13 out of 18 fish habitat attributes, and the three hydrographic data sets differed significantly for many characteristics in streamside buffers; fish distributions mapped at 1:24 000 added 6 to 14 percent of stream length to 1:100 000. distributions. The analysis of spatial position found few differences between the 1:100 000 and 1:24 000 hydrography in streamside buffer characteristics but significant differences in channel gradient.
4. Overall, hydrographic data sets differed only slightly in spatial position but differed in spatial extent to the point of representing different populations of streams. If species inhabiting larger streams (greater mean annual discharge) are of interest, then results derived from studies based on 1:100 000 hydrography should prove useful. However, higher resolution hydrography can be critical when designing and implementing strategies to protect fish and other aquatic species at risk in smaller streams.
Keywords: freshwater conservation, stream analysis, streamside conditions, fish distribution, spatial extent, spatial position, spatial resolution, cartographic scale
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Vance-Borland, K.; Burnett, K.; Clarke, S. 2009. Influence of mapping resolution on assessments of stream and streamside conditions: lessons from coastal Oregon, USA. Aquatic Conservation: Marine and Freshwater Ecosystems. 19: 252-263.
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