Modelling the possible Debris Flow events in Swat Mountains Using Flow-R -A Case Study in Pakistan

Abstract

Debris flows are dangerous mixtures of water, sediment, and rock that can cause serious problems in mountainous regions.These destructive events happen often in mountain areas, especially during floods and intensive rain fall. The purpose of this study is analyse the possible debris flow events in Swat mountains in Pakistan using Flow-R. Flow-R is a debris flow simulation software that generates susceptibility maps, offering critical insights into the areas most prone to this hazardous phenomenon. The primary inputs required for the Flow-R simulation were digital elevation models (DEM) and the source area file of the region. Two specific algorithms, Holmgren modified and Gamma 2000, have been taken into consideration for this case study. Holmgren Modified considers various factors like topography, climate, vegetation, and land use, while Gamma 2000 focuses on rock type’s influence on debris flow occurrences. By integrating these inputs with the selected algorithms, Flow-R generated susceptibility maps, highlighting three regions: Thal, Kalam, and Kandia Valley, with varying degrees of vulnerability to debris flow events. According to the susceptibility map of Holmgren modified among three regions, the Thal region is highly susceptible to debris flows due to its topography as compared to Kalam and Kandia Valley. On the other hand, the susceptibility map of Gamma 2000 shows that in the Thal region, large rocks contribute more, while in the other two regions, small rocks are mainly responsible for generating debris flow. By identifying the areas most susceptible to debris flows, effective risk mitigation measures can be implemented to reduce potential damage and protect vulnerable communities.