Topographic roughness on forested hillslopes: a theoretical approach for
quantifying hillslope sediment flux from tree throw
Abstract
Tree uprooting 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 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 dimensionless variable that is the ratio of
fluxes due to three throw versus creep-like processes. Applying the
theory to hillslopes in Southern Indiana, we find that tree throw
accounts for 10 to 20\% of the hillslope sediment flux.
The theoretical and observational findings provide a framework and
important constraints on quantifying Critical Zone function from
topographic parameters such as roughness.