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Parameter Sensitivity in Hydrologic Modeling - page 138 / 163





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increase in longest flow path using CRWR-PrePro, and a 12% increase using WMS. For the large area, Area 3, there was a 3% increase in longest flow path using CRWR-PrePro and a 2% increase using WMS. Regardless, the longest flow path standard deviation for Area 1 is 0.13 miles (with a mean of 1.58 miles), and the longest flow path standard deviation for Area 3 is 0.22 miles (with a mean of 6.67 miles). Variations are small, and results show that these variations do not significantly influence lag time and discharge calculations. Distributed properties such as slope and longest flow path require a method or model to reduce the distributed information into a representative value for the entire subcatchment. Variations in subcatchment slope and longest flow path values between WMS and CRWR-PrePro may be attributed to differences in underlying models used for extracting data.


Parameter Extraction Using TINs

TINs, triangulated irregular networks, consist of a set of vertex points connected by triangles, that represent scattered X, Y, and Z locations. TINs have many advantages over DEMs, in that TINs can describe a surface precisely and are adaptive to different types of terrain. The major disadvantage found working with TINs in this project is the large amount of time that is required to create, edit, and condition the TIN. For this reason, TIN development was not conducted for Area 3. Parameter values for area, perimeter, and longest flow path did not vary significantly for the TIN when compared to the DEM methods and on-screen digitizing. Slope measurement using a TIN, however, produced a greater value


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