Experimental testing of a stochastic sediment transport model

A stochastic model of sediment transport by rainfall-runoff was tested with a simple laboratory experiment. Although the conceptual basis of the model has been previously published [Lisle, I.G., Rose, C.W., Hogarth, W.L., Hairsine, P.B., Sander, G.C., Parlange, J.-Y., 1998. Stochastic sediment transport in soil erosion. Journal of Hydrology 204, 217–230] and its mechanistic underpinnings were convincingly theorized, it had not been corroborated with measurements. Small-scale flume experiments, ∼0.8 m long, with simulated rainfall were used to imitate “wash-off” of sediment (0.225 mm silica sand) from an impervious surface. Fitting two parameters (ejection and deposition rates) to minimize least squares error resulted in good agreement between stochastic model and measurements, R2 ∼ 0.9. However, the fitted parameter values differed from values that would be expected following Lisle et al.’s (1998) physical explanation of the ejection and deposition rates. While some of the discrepancy may be attributable to particle interactions, the conceptualization of deposition as a quiescent settling process in mechanistic erosion models may need to be reevaluated.