What do the rocks tell us? : A look at Tanjong Riamu's January 2021 landslides

Abstract

Landslides were reported along Singapore’s remaining natural rocky cliff and shore - Tanjong Rimau in early January 2021. Most historical landslides in Singapore are attributed to heavy and intense rainfall events that led to the failure of engineered slopes. However, Tanjong Rimau’s landslides represent a unique case as they occurred along natural rocky slopes. These slopes comprise both the bedrock and the layer of residual soil. In this study, we aim to provide explanations about the failure mechanisms and the factors that contributed to the slope failure. We achieve this through a series of analysis. First, we dig deep into the literature and engage in field studies to understand the underlying geology. Next, we tapped on UAV Photogrammetry techniques to document the evolution of the landslides and quantify the impact on the slope. Then, we analyzed the time-series images collected from these field studies. Lastly, we gathered historical rainfall data across relevant weather stations to explore its effects on the reported landslide events.

Through our study, we conclude with certainty that the underlying bedrock geology controls the stability of the slopes along Tanjong Rimau. The landslides reported in January 2021 result from the bedrock collapse at its toe in response to heavy rainfall. Our findings also suggest that the disrupted slopes are progressing towards achieving a new structural equilibrium. Using these interpretations, we propose to pay more attention to slopes along Tanjong Rimau with similar characteristics, as they might mirror this landslide process in future events.