Utilizing Various Geospatial Data for Debris Flow Geological Hazard Characterization and Mapping at Jerai Geopark, Malaysia

Gunung Jerai, or Mount Jerai, is in northern Malaysia, a tropical forest where the intrusion of the granitic batholith and metasedimentary rocks controls the topographical condition. Due to the geological aesthetic and the socio-economic history, Gunung Jerai was gazetted as a National Geopark named Jerai Geopark. The geological disaster at Gunung Jerai on 18th August 2021 significantly impacted approximately 1000 families in the region, driven by a maximum cumulative rainfall of around 200mm per 3 hours. This study aims to determine the geological and geomorphological characteristics of the debris flow event on 18th August 2021, which affects mainly three catchments: Seri Perigi Catchment, Batu Hampar Catchment, and Titi Hayun Catchment by using geospatial technique. Three main remote sensing techniques were utilised to achieve the aim of the study, namely IfSAR, LiDAR, and photogrammetry. Aerial photogrammetry was conducted using fixed-wing UAVs with mounted camera sensors covering the catchment areas to visualise the current terrain condition after the debris flow event, which is utilised for the individual landslide inventory, debris flow path, formation of the natural temporary dam, and deposition of the debris flow materials. LiDAR was also employed separately using multi-rotor UAV to conduct detailed terrestrial mapping of selected major landslides to determine landslide classification such as landslide type, dimensions, activity, distribution, and causal factors. At the regional scale, DEM from IfSAR and field geological mapping is utilised for demarcation and delineation of geomorphological features and to generate morphometric data, including slope curvature, slope gradient, slope aspect, flow direction, and flow accumulation, which is derived from the DEM. This information is crucial for disaster management and mitigation efforts, aiding in better preparedness and response. These abstract aims to explain how each geospatial data is utilised and optimised to characterise the debris flow disaster event.