Risk assessment of flash flood situation under land use change using daily SWAT streamflow simulation in Loei Basin, Northeastern, Thailand

Abstract

Flash flood typically occurs in the wet season caused by heavy rain from upstream to downstream and land use changes. This research mainly aims to apply SWAT model to assess the variation of streamflow in Loei Basin, Northeastern Thailand by comparing the daily streamflow during flash flood in the rainy season in the years 2002, 2011, and 2017. This included considering the three different time periods of land use change patterns input to SWAT to assess the impact on streamflow. The result revealed that daily SWAT streamflow simulation compared to data obtained from KH58A station in 2011 was reliable as could be seen from acceptable R2 and PBIAS. In terms of the tendency of land use change, conventional agricultural was replaced with rubber plantation, sugarcane, and urbanization. From this situation, most flood risk areas occur along the mainstream from middle to northern of basin outlet, including being a municipal community area with a high density of residents. It is expected to be a risky area affected by the flood situation. The result of this research can be used as a guideline for land use and water resource management when encountering sudden changes in hydrologic conditions in the wet season.

Application of SWAT Model for Assessment of Surface Runoff in Flash Flood Areas

“…The highest maximum runoff value was from the Chern River Basin Part 1. In addition, it was found that the highest occurrence of runoff happened in two periods, September (dry season-flood season) and October (flood season-dry season) of every land use year in all three river basins, as previously reported [43,[55][56][57]. Therefore, it can be concluded that recent land use changes under the highest annual rainfall will cause the basin's highest runoff.…”

“…In the past, the SWAT model has been applied to assess runoff from changes in climate conditions and various land uses [39][40][41][42]. In Thailand, there have been various analyses of land use changes on runoff that also used SWAT models [43]. However, this study was limited to a single watershed and did not map past land use changes over a sufficiently long timescale.…”