Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/nhess-2018-109
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
12 Jun 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Natural Hazards and Earth System Sciences (NHESS).
How size and trigger matter: analyzing rainfall- and earthquake-triggered landslide inventories and their causal relation in the Koshi River basin, Central Himalaya
Jianqiang Zhang1,2, Cees J. van Westen2, Hakan Tanyas2, Olga Mavrouli2, Yonggang Ge1, Samjwal Bajrachary3, Deo Raj Gurung3, Megh Raj Dhital4, and Narendral Raj Khanal5 1Key Laboratory of Mountain Hazards and Surface Process/Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu, China
2Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, the Netherlands
3International Centre for Integrated Mountain Development (ICIMOD), Lalitpur, Nepal
4The Department of Geology, Tri-Chandra Multiple Campus, Ghantaghar, Kathmandu, Nepal
5Central Department of Geography, Tribhuvan University, Kathmandu, Nepal
Abstract. Inventories of landslides caused by different triggering mechanisms, such as earthquakes, extreme rainfall events or anthropogenic activities, may show different characteristics in terms of distribution, causal factors and frequency-area relationships. This research aims to study such differences in landslide inventories, and the effect they have on landslide susceptibility assessment. Koshi River basin in central Himalaya was taken as study area. Detailed landslide inventories were generated based on visual interpretation of remote sensing images and field investigation for different time periods and triggering mechanisms. Maps and images from the period 1992 to 2015 were used to map 5,858 rainfall-triggered landslides and after the 2015 April 25 Gorkha earthquake, an additional 1138 co-seismic landslides were mapped. A set of topographic, geological and land cover factors were employed to analyze their correlation with different types and sizes of landslides. The results show that the frequency – area distributions of rainfall and earthquake–triggered landslides varied considerably, with the former one having a larger frequency of small landslides. Also topographic factors varied considerably for the two triggering events, with both elevation and slope angle showing significantly different patterns for earthquake-triggered and rainfall-triggered landslides. Landslides were classified into two size groups, in combination with the main triggering mechanism (rainfall- or earthquake-triggered). Susceptibility maps for different combinations of landslide size and triggering mechanism were generated using logistic regression analysis. The different triggers and sizes of landslide data were used to validate the models. The results showed that susceptible areas for small and large size rainfall- and earthquake-triggered landslides differed substantially, while susceptibility maps for different size of earthquake-triggered landslides were similar.
Citation: Zhang, J., van Westen, C. J., Tanyas, H., Mavrouli, O., Ge, Y., Bajrachary, S., Gurung, D. R., Dhital, M. R., and Khanal, N. R.: How size and trigger matter: analyzing rainfall- and earthquake-triggered landslide inventories and their causal relation in the Koshi River basin, Central Himalaya, Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2018-109, in review, 2018.
Jianqiang Zhang et al.
Jianqiang Zhang et al.
Jianqiang Zhang et al.

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Short summary
The aim of this study is to investigate the differences in the mappable characteristics of earthquake-triggered and rainfall triggered landslides in terms of their frequency-area relationships, spatial distributions and relation with causal factors, and to evaluate whether separate susceptibility maps generated for specific landslide size and triggering mechanism are better than a generic landslide susceptibility assessment including all landslide sizes and triggers.
The aim of this study is to investigate the differences in the mappable characteristics of...
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