Modeling the Effects of Vertically Variable Soil Parameters and Hillslope Shape on Runoff

Soil parameters used in hydrologic modeling, such as porosity, volumetric water content, and saturated hydraulic conductivity (Ksat) are commonly known to be variable over depth within the soil profile, however these parameters are often modeled as single values, constant over depth. Also, hillslopes found in glacial till features of Connecticut tend to have an S-shaped profile over distance. This study proposes that using variably vertical soil parameters and hillslope shape has effects on runoff modeling results. The effects of vertical soil heterogeneity and hillslope shape on runoff production are evaluated by comparing soil water drainage and runoff production from different vertical distributions of the soil parameters in a hydrologic model of a hillslope. A mass-balance finite-difference hydrologic model of hypothetical hillslopes is developed for use in saturation overland flow modeling. The impacts of changes in physical soil properties such as porosity, volumetric water content, and saturated hydraulic conductivity with depth are evaluated. Timing and amount of runoff for a uniform rainfall are compared for an S-shaped vs. straight hillslope. The dynamic modeling package STELLA® was used to develop the model