Landslide risk assessment using hydrological model in the Upper Yom River Basin, Thailand

Abstract This study applied the Block wise application of TOPMODEL with the Muskingum-Cunge routing method (BTOPMC) for a river runoff simulation and landslide risk assessment in the Upper Yom River Basin. The physical characteristics of the watershed are indicated by concerning the Digital Elevation Model (DEM), land use, and soil types. The hydrological data used for simulation and model performance investigation consist of hourly rainfall intensity and river discharge during the heavy rainfall periods. The consistency between the simulated results and observed data is statistically investigated by Nash-Sutcliffe coefficient of efficiency. The slope failure was analyzed using the slope-instability analysis method with the groundwater level and soil topography index obtained from hydrological simulation. The landslide vulnerable areas are spatially indicated as the area having a Factor of Safety (FS) less than one. The results show that BTOPMC provides a high potential for the hourly simulation of the hydrological regime in the Upper Yom River Basin during high rainfall intensity. In addition, it is revealed that heavy rainfall that happened in studied scenarios cannot cause slope failure. However, several locations show Factor of Safety (FS) values between 1.01 and 3.00, such as the Pong District in Phayao Province, meaning that these areas are vulnerable to landslide events when facing negligible increased precipitation. The analyzed vulnerable landslide areas are similar to those displayed in the landslide risk map presented by the Land Development Department of Thailand. Therefore, this is trustworthy for using in the landslide warnings policy to mitigate the loss of lives and assets.