Mapping Debris Flow Susceptibility Using Frequency Ratio Model in Kundasang, Sabah, Malaysia

Debris flows are significant geological hazards that pose severe risks to human settlements and natural environments. The Crocker Range in Sabah, Malaysia, exemplifies the complex interactions between geological hazards and human activities. This study comprehensively assesses debris flow susceptibility in the Kundasang area of Sabah, utilizing a bivariate Frequency Ratio (FR) model integrated within a Geographic Information System (GIS). Key terrain parameters such as slope aspect, slope curvature, elevation, land use, slope angle, soil association, Stream Power Index (SPI), stream proximity, and Topographic Wetness Index (TWI) are examined to identify the factors influencing debris flow occurrences. The findings indicate that slope aspect, curvature, and elevation play critical roles, with concave and north-facing slopes between 2500 m and 3000 m elevation being highly susceptible due to population density and land use practices. Primary dryland forests and steep slopes, combined with specific soil associations, further increase susceptibility. SPI and proximity to rivers highlight areas of elevated risk, particularly within 100 m of rivers, while TWI reflects increased vulnerability linked to soil water content. By integrating these parameters, the study generates a detailed debris flow susceptibility map, which classifies the southern region, including populated areas, as highly vulnerable. This map provides crucial insights for practical application in land-use planning, forest management, and infrastructure development to mitigate debris flow risks. The study's findings empower policymakers, researchers, and local communities with actionable strategies to safeguard lives and ecosystems against debris flow hazards. Condensed recommendations focus on proactive land-use planning and sustainable forest management to reduce future risk.