Erosion prediction on unpaved mountain roads in northern Thailand: validation of dynamic erodibility modelling using KINEROS2

The event- and physics-based KINEROS2 runoff/erosion model for predicting o verland flow generation and sediment production was applied to unpaved moun tain roads. Field rainfall simulations conducted in northern Thailand provi ded independent data for model calibration and validation. Validation shows that KINEROS2 can be parameterized to simulate total discharge, sediment t ransport and sediment concentration on small-scale road plots, for a range of slopes, during simulated rainfall events. The KINEROS2 model, however, d id not accurately predict time-dependent changes in sediment output and con centration. In particular, early flush peaks and the temporal decay in sedi ment output were not predicted, owing to the inability of KINEROS2 to model removal of a surface sediment layer of finite depth. After 15-20 min, sedi ment transport declines as the supply of loose superficial material becomes depleted. Modelled erosion response was improved by allowing road erodibil ity to vary during an event. Changing the model values of erosion detachmen t parameters in response to changes in surface sediment availability improv ed model accuracy of predicted sediment transport by 30-40%. A predictive r elationship between road erodibility 'states' and road surface sediment dep th is presented. This relationship allows implementation of the dynamic ero dibility (DE) method to events where pre-storm sediment depth can be estima ted (e.g., from traffic usage variables). Copyright (C) 2001 John Wiley & S ons, Ltd.