Comparison of Stream Reach Lengths Measured in the Field and from Maps

We evaluated two methods of stream reach length measurement: hip chain measurements and map measurements made with MapTech Terrain Navigator software. Fifty stream segments ranging from 0.3 to 4.2 km were selected for measurement in Oregon coastal watersheds. Each stream segment was measured twice with each method by each of two surveyors, for a total of eight measurements per site. Map measurements were more precise than hip chain measurements. The difference between the two methods of measurement was slight but significant. The 95% confidence interval of the difference between the two measurements ranged from 0.035 to 0.225 km. Map-based lengths explained 85% of the variation in stream lengths measured with a hip chain. The coefficients of the regression equations indicated a 1:1 correspondence between the two methods of measurement. Our results suggest that map-based estimates provide a less-intrusive alternative to stream reach measurements made with a hip chain.