could be approximated within ± 0.05 as percent slope (a CV of 3.65%). The mean slope for Area 3 was 0.77%, while the mean slope for Area 1 was 1.30%.
Longest Flow Path
Longest flow path results produced errors greater than slope or area errors for all three study areas. However, this error decreased from 8.42% to 3.22% as the study area size increased from Area 1 to Area 3. For the largest area, longest flow path was calculated within ± 0.22 miles, with a mean value of 6.67 miles. For the smallest area, longest flow path was calculated within ± 0.13 miles, with a mean value of 1.58 miles.
Watershed perimeter length, although not a hydrologic parameter, was
methods using DEMs produced greater values for perimeter
methods for all three study for perimeter. For Area 1, value was 14.99%.
areas. the CV
This resulted in consistently value was 10.28%, and for
than traditional high CV values Area 3, the CV
The SCS runoff curve number obtained by combining land use and soil types in GIS for Area 2 was 91.7, while the curve number determined by an independent TxDOT study was 85.8. A range of curve number values, using the