From Idiosyncrasies to Interactions: Systematic Exploration of the Soil Controls on Subsurface Lateral Flow at the Hillslope Scale

The links between soil characteristics and subsurface lateral flow at the hillslope scale are poorly understood. Much of the work to date has focused on the idiosyncrasies of different individual hillslopes. As a result, a general framework for hydropedological characterization is still lacking. This presentation explores how models can be used to identify the hierarchy of soil controls on subsurface lateral flow. We present a number of virtual experiments using a 3D physics-based finite element model to systematically investigate the interactions between soil depth, soil hydraulic properties and slope angle on subsurface lateral flow generation, timing and magnitude. Our base case model domain is the 28 x 48 m Panola experimental hillslope in Georgia USA. We use Panola as a shell for these simulations where we build and calibrate the model using the measured soil surface and subsurface geometry. The parameterization of the soil and bedrock properties is based on detailed field measurements at the site. Following calibration, topography and soil characteristics were varied to establish response surfaces between controlling variables. We discuss the interactions between these variables and how different soil assemblages characterize internal hillslope response and resultant lateral flow.