Review of trigger thresholds for landslides in tropical residual soils

Nedumpallile Vasu, Nikhil; Banks, Vanessa; Arnhardt, Christian; Mansour, Majdi; Ougier-Simonin, Audrey. 2022 Review of trigger thresholds for landslides in tropical residual soils. [Lecture] In: International Conference On Engineering Geology and Geotechniques for Safe and Sustainable Infrastructures, Novotel Hotel, Kolkata, 16-17 Nov 2022. (Unpublished)

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Tropics make up about 40% of the earth’s surface area and are home to approximately 40% of the world’s population [1]. Significant and variable depths of residual soils occur across tropical regions for instance Southern India, South-West China, Malaysia, Africa, Taiwan, Hong Kong, Singapore, Sri Lanka, the Philippines, and Northern Brazil. Rapid development in these countries, coupled with changing climate, results in an increasing number of landslides affecting people, property, and livelihoods. Step changes in landslide risk management can be achieved through landslide susceptibility mapping in conjunction with the determination of thresholds at which landslides might be initiated. The landslide trigger thresholds can be defined as a condition that when overcome can cause a change in the state of a system or landscape resulting in one or more landslides [2]. These thresholds can be developed at different spatial scales using approaches such as process-based, conceptual, empirical, statistical, or probabilistic methods [3]. The existing review of studies on trigger thresholds by [2] highlights the challenges of limited landslide inventories, quality of datasets, need for objectivity and reproducibility, and validation. The landslide trigger threshold in tropical countries mostly uses empirical or data-driven methods, which are usually based on incomplete and/or impact-biased landslide inventories. The incomplete or limited landslide inventory further limits the development of the threshold considering the regional or domain-specific ground-based information such as geology, geomorphology, climate, and hydrology. Therefore, the resulting trigger thresholds at regional-scale in a tropical setting are less reliable for landslide forecasting-based applications. The landslides in tropical residual soils may not always directly correlate to rainfall amount or rainfall intensity owing to the importance of soil properties [4], derived from the underlying geology and anthropogenic interventions. Furthermore, the dynamic nature of land use and climate change means that trigger thresholds need to account for these processes to be more effective in tropical regions, and not just be reliant on the historical landslide record. This review study aims to address the current gap in trigger threshold research for tropical residual soils and put forward the case to consider approaches that integrate the ground information. The current review forms part of the “Landslide trigger thresholds for tropical residual soils” project funded by the BGS International Geoscience Research and Development (IGRD) programme. The project aims to benefit community resilience against landslide risk in tropical residual soil regions through better forecasting of rainfall-induced landslides. Pilot studies will be conducted in Southern India and research outputs transferred to comparable sites in Southeast Asia.

Item Type: Publication - Conference Item (Lecture)
Additional Keywords: IGRD
Date made live: 24 Aug 2023 13:13 +0 (UTC)

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