Topographic Roughness on Forested Hillslopes: A Theoretical Approach for Quantifying Hillslope Sediment Flux From Tree Throw

Abstract

AbstractWind‐driven tree throw is an observable and consequential process that suddenly moves soil downslope, inverts the soil column, and roughens the surface with pit‐mound topography. Quantifying fluxes due to tree throw is complicated by its stochastic nature and estimation requires averaging over a large area or long time. Here, we develop a theory that leads to a dimensionless metric directly measurable from high resolution topographic data. The theory explains the flux and topographic roughness as a function of tree throw production and decay rate by creep‐like processes. We then form a measurable dimensionless variable that is the ratio of fluxes due to tree throw versus creep‐like processes. Applying the theory to hillslopes in Southern Indiana, we find that tree throw accounts for 11%–18% of the hillslope sediment flux. The theoretical and observational findings provide important constraints on quantifying Critical Zone function from topographic parameters such as roughness.