Geological Factors Contributing to Landslide Incident in Malaysia - Case Study Batang Kali Landslide Disaster, Hulu Selangor, Selangor.

Abstract

The Batang Kali landslide that occurred at 2.08 a.m. on 16 December 2022 had struck almost entirely the agriculture and campsite areas of Father's Organic Farm, Batang Kali, Hulu Selangor, Selangor. The deadly landslide claimed 31 lives including 13 children and 61 survivors were rescued. The search and rescue (SAR) operation was carried out immediately and continued for nine days before it ended after the last victim was found. The Department of Mineral and Geoscience Malaysia (JMG) was informed of the event and actively involved in conveying geological information during the SAR operation. JMG was also responsible for conducting a forensic investigation to understand the geological factors that contributed to this catastrophic event. An extensive field geological study including LiDAR data capture, geophysical surveys, geological surface mapping, hydrogeological, and in situ field testing were carried out. These data were analyzed to ascertain the causal geological factors and establish of subsurface profile for landslide simulation modeling. The landslide is classified as a complex which is a combination of rotational slide and earth flow. The landslide body measured approximately 550m long, 110m wide, and 14m deep with 282,170m³ total estimated volume of debris which mainly consists of sandy silt beside block boulders and tree trunks. Analyses indicate that the colluvium layer which is deposited at the foot slope and the groundwater regime have contributed significantly to the failure. Landslide simulation modeling shows the velocity of the flow is 13.2m/s with the average thickness of the accumulation zone ranging from 0.8m to 10.5m. The result from the investigation also indicates that geological causal factors should be taken into consideration in slope repair works and mitigation measures.