Preprints
https://doi.org/10.5194/nhess-2020-259
https://doi.org/10.5194/nhess-2020-259

  25 Aug 2020

25 Aug 2020

Review status: a revised version of this preprint was accepted for the journal NHESS and is expected to appear here in due course.

The role of geomorphology, rainfall and soil moisture in the occurrence of landslides triggered by 2018 Typhoon Mangkhut in the Philippines

Clàudia Abancó1, Georgina L. Bennett1, Adrian J. Matthews2, Mark A. Matera3, and Fibor J. Tan3 Clàudia Abancó et al.
  • 1College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4RJ, United Kingdom
  • 2Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences and School of Mathematics, University of East Anglia, Norwich, NR4 7TJ, United Kingdom
  • 3School of Civil, Environmental and Geological Engineering, Mapua University, Manila, Philippines

Abstract. In 2018, Typhoon Mangkhut (locally known as Typhoon Ompong) triggered thousands of landslides in the area of Itogon (Philippines). A landslide inventory of 1101 landslides over a 570 km2 area is used to study the geomorphological characteristics and land cover more prone to landsliding as well as the rainfall and soil moisture conditions that led to widespread failure. Landslides mostly occurred in slopes covered by wooded grassland in clayey materials, predominantly facing East–Southeast. The analysis of both satellite rainfall (GPM IMERG) and soil moisture (SMAP-L4) finds that, in addition to rainfall from the typhoon, soil water content plays an important role in the triggering mechanism. Rainfall associated with Typhoon Mangkhut is compared with 33 high intensity rainfall events that did not trigger regional landslide events in 2018 and with previously published rainfall thresholds. Results show that: (a) it was one of the most intense rainfall events in the year but not the highest, and (b) despite satellite data tending to underestimate intense rainfall, previous published regional and global thresholds are to be too low to discriminate between landslide triggering and non-triggering rainfall events. This work highlights the potential of satellite products for hazard assessment and early warning in areas of high landslide activity where ground-based data is scarce.

Clàudia Abancó et al.

 
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Status: closed
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Clàudia Abancó et al.

Clàudia Abancó et al.

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Short summary
In 2018, Typhoon Mangkhut triggered thousands of landslides in the area of Itogon (Philippines). A landslide inventory of 1101 landslides revealed that landslides mostly occurred in slopes covered by wooded grassland in clayey materials, predominantly facing E–SE. The rainfall event was one of the most intense in the year but not the highest. Several rainfall events exceeded previously published rainfall thresholds for landslides, which are too low to identify landslide triggering rainfalls.
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