The fluvial erosion / transport equation of landscape evolution models revisited

(512x128).(reference)Abstract. We present a meso-scale erosion/deposition model, which differs from previous Landscape Evolution Models equations by taking explicitly into account a mass balance equation for the stream flow. The geological and hydrological complexity is lumped into two basic fluxes, erosion and deposition, and two averaged parameters: unit width discharge q and stream slope s. The model couples the dynamics of stream flow and topography through a sediment transport length function (q), which is the average travel distance of a particle in the flow before being trapped on topography. This property reflects a time lag between erosion and deposition, which allows the stream flow not to be instantaneously at capacity. The so-called -q model may reduce either to transport-limited (TL) or to detachment-limited (DL) erosion modes depending on . But it also may not. We show in particular how it does or not for steady-state topographies, long term evolution, and high-frequency base-level perturbations. Apart from the unit-width discharge and the settling velocity, the (q) function depends on a dimensionless number encompassing the way sediment is transported within the stream flow. Using models of concentration profile through the water column, we show the dependency of this dimensionless coefficient on the Rouse number. Finally we discuss how consistent the -q model framework is with bedload scaling expressions and Einstein’s conception of sediment motion.

Journal of Geophysical Research – Earth Surface, 114, doi:10.1029/2008jf001146, 2009.
Philippe Davy and Dimitri Lague
Géosciences Rennes, UMR 6118 CNRS, Université de Rennes I, Campus de Beaulieu, 35042 Rennes Cedex, France