Estimation of Soil Parameters for Assessing Potential Wetness: Comparison of Model Responses Through Gis

Abstract

A geographic information system (GIS) is utilized to model wetness potential for a portion of Uwharrie National Forest, North Carolina. The wetness index is derived from TOPMODEL, a hillslope-scale runoff simulation model. The wetness index is a distributed-parameter model, with the input parameters obtained from a digital elevation model (DEM) and Soil Conservation Service (SCS) soils data. The primary objectives of the research are to: (1) compare methods of estimating soil parameters for input into the wetness potential model; and (2) determine how the model outputs vary spatially as a consequence of different methods of estimating soil parameters. Three methods of estimating soil parameters are used: (a) assuming uniform soil properties; (b) using SCS data presented as ranges; and (c) using alternative literature-based estimates of soil parameters. Results indicate that the wetness model responds similarly regardless of how the soil parameters are estimated, but differences in the spatial variability of the wetness potentials occur as a result of estimating soil parameters through alternative approaches. Correlation, pair-wise regression and analysis of regression residuals are used to compare model responses within a GIS environment.

Geographic Information Systems

“…Model results compared favorably with recorded stream flows for 77 rain events (Zollweg et al, 1996). A GIS was used to model runoff potential for a portion of Uwharrie National Forest, North Carolina, with the input parameters obtained from a digital elevation model (OEM) and Soil Conservation Service (SCS) soils data (Townsend and Walsh, 1996).…”