New Landslide Inventory and Assessment in Malaysia: A Geological and Geomorphological Modelling Approach

Landslide remained the major natural hazards that contributed to higher number of human losses and new emerging disaster in a densely populated hillslope region in Malaysia. Landslides and slope failure in Bukit Antarabangsa, Ampang, Selangor have been progressively studied since the tragedy of Highland Tower in 1993, followed by Taman Hillview Landslide (2002) and Taman Bukit Mewah Landslide (2008). The tragedies cause damage to the properties, casualties, and economic losses. This study provides a new insight into landslide assessment based on newly developed inventories as a result of the geological and geomorphological modelling approach in the old hilly residential city in the Selangor, the riches state that contributed to 30% national GDPs. This project assessed landslide inventory, vulnerability and geological risk based on four elements-at-risk (EaR): buildings, roads, man-made slopes, and socio-economy, after the landslide in Taman Kelab Ukay in 2020. The indicator and sub-indicator of EaR about the geological and geomorphological features are emphasised for the landslide vulnerability assessment, e.g. susceptibility of the element-at-risk and the landslide intensity. This paper aims to explain the geological and geomorphological approach for landslide vulnerability assessment as performed in this area. Six methodologies were conducted to explore semi-quantitative landslide vulnerability assessment: geological mapping, discontinuity and structural mapping, slope inventory and landslide inventory using proforma, geophysical survey, remote sensing and GIS analysis, and engineering geological modelling. Based on the mapping, the granite and schist in Bukit Antarabangsa shown weathering ranges between Grade III and Grade V, where the weathering profile and the geological structures highly influence the topography and major fault zone in this area, known as the Kuala Lumpur Fault Zone. Discontinuity mapping was conducted to determine the structural pattern and the kinematic stability of selected rock slopes. Geophysical surveys using the electrical resistivity tomography method were employed to determine the subsurface and groundwater conditions, especially in the potential and historical landslide area. Hillslope analysis was conducted to identify the topographical and hydrological pattern associated with the characteristics of potential geological hazards, namely channelised catchment, topographic depression, and open hillslope. Landslide inventory was also interpreted using GIS and remote sensing analysis to characterise it into 1) potential initiation zone and 2) potential transportation and depositional zone. As a result, one hundred forty-nine (149) slopes have been inventoried, and eighty-nine (89) potential landslides have been geomorphologically identified. Three areas have been selected to construct engineering geological maps and models due to engineering concerns with the support of significant inventory mapping activities, subsurface investigation, and discontinuity survey. The model and map provide output for further landslide risk assessment, planning for future development, and anticipation of potential geological hazards. As a conclusion, this multi-sectoral and transdisciplinary study explores a new insight into advanced landslide mapping and technological-based assessment at a city-level for better understanding the landslide causes, rejuvenating impacts and exploring possible mitigation measures to prevent future disaster losses in a tropical environment.