Analysis of landslide-triggering rainfalls in a typhoon-prone region of the Philippines
- 1University of Barcelona, Faculty of Earth Sciences, Department of Mineralogy, Petrology and Applied Geology, Barcelona, Spain (claudia.abanco@ub.edu)
- 2BarcelonaTECH, Department of Civil and Environmental Engineering, UPC, Division of Geotechnical Engineering and Geosciences, Barcelona, Spain
- 3University of Exeter, College of Life and Environmental Sciences, Department of Geography, Exeter, UK
- 4University of East Anglia, Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences / School of Mathematics, Norwich, UK
The rain that falls weeks or months before the occurrence of landslides can play a major role in the failure process, therefore it is crucial to account for it in hazard assessments and warning systems. It is especially relevant in tropical areas, where the amount of water that falls during wet seasons can be very high. In the Philippines, rainfall and typhoon events trigger Multiple-Occurrence Regional Landslide Events (MORLEs, Crozier, 2005), which cause hundreds of fatalities and significant economic damage every year.
Satellite-based rainfall measurements (IMERG GPM) associated with three typhoons that triggered MORLEs in the area of Itogon (Benguet, Philippines) and water infiltrated into the soil during the previous months are analysed. Data from the three typhoons are compared with 560 high intensity rainfall events (from period 2000-2020) that did not trigger regional landslide events. Results show that landslides occurred when typhoon rainfall exceeds 300 mm and the water infiltrated was higher than 1000 mm in the previous months. For one specific landslide-triggering typhoon event, satellite-based soil moisture data (1 m top soil layer) are analysed and compared to other non-landslide triggering rainfalls. Results do not show a clear correlation of critical rainfall and soil moisture values that triggered landslides.
The findings of this work highlight that the antecedent rainfall, and in particular its infiltration below the top soil layer, plays a major role in the triggering process of landslides, especially in tropical regions.
Crozier, M.J. Multiple-occurrence regional landslide events in New Zealand: Hazardmanagement issues. Landslides 2, 247–256 (2005). https://doi.org/10.1007/s10346-005-0019-7
How to cite: Abancó, C., Medina, V., Bennett, G. L., Matthews, A. J., and Hürlimann, M.: Analysis of landslide-triggering rainfalls in a typhoon-prone region of the Philippines, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7819, https://doi.org/10.5194/egusphere-egu22-7819, 2022.
