Identification of vulnerable regions to soil loss under the dynamic saturation process

This study presents a theoretical framework based on power law distribution to identify the vulnerable regions to soil loss in Susu river basin at Cameron Highlands, Malaysia by using the geomorphologic factors from Digital Elevation Model (DEM). Drainage area is used to describe the runoff aggregation structure of the watershed which represents the magnitude of discharge. Stream power is also used to describe the energy expenditure pattern of the watershed. They are fitted to power law distribution by means of the maximum likelihood to estimate the threshold for soil loss. The landscape stability condition is assessed through the mechanism of channel initiation. Two regions in the slope area plot are recognized as the regimes susceptible to soil loss, in that discharge, local slope and energy are sufficient for the initiation of soil movement. The result is further improved by incorporating the Topographic Wetness Index (TWI) aiming to locate vulnerable regions to soil loss under the dynamic saturation process. The final result indicates that the vulnerable regions expand from perennial reaches to ephemeral reaches as saturation process develops. It implies the transition of runoff generation from groundwater in perennial reaches to surface runoff in ephemeral reaches. Identification of soil loss vulnerable regions under the dynamic saturation process helps in planning of the mitigation measures for soil erosion.