Characterizing the evolution life cycle of the Sunkoshi landslide in Nepal with multi-source SAR data

Meng Ao,Lijun Su,Yuting Dong,Lu Zhang,Xuguo Shi,Mingsheng Liao,Timo Balz

doi:10.1038/s41598-020-75002-y

Abstract

A catastrophic landslide disaster happened on 2 August 2014 on the right bank of Sunkoshi River in Nepal, resulting in enormous casualties and severe damages of the Araniko highway. We collected multi-source synthetic aperture radar (SAR) data to investigate the evolution life cycle of the Sunkoshi landslide. Firstly, Distributed Scatterers SAR Interferometry (DS-InSAR) technology is applied to analyze 20 ALOS PALSAR images to retrieve pre-disaster time-series deformation. The results show that the upper part, especially the top of the landslide, has long been active before collapse, with the largest annual LOS deformation rate more than − 30 mm/year. Time series deformations measured illustrate that rainfall might be a key driving factor. Next, two pairs of TerraSAR-X/TanDEM-X bistatic data are processed to identify the landslide affected area by intensity change detection, and to generate pre- and post-disaster DSMs. Surface height change map showed maximum values of − 150.47 m at the source region and 55.65 m in the deposit region, leading to a debris volume of 5.4785 ± 0.6687 million m3. Finally, 11 ALOS-2 PALSAR-2 and 82 Sentinel-1 SAR images are analyzed to derive post-disaster annual deformation rate and long time series displacements of the Sunkoshi landslide. The results illustrated that the upper part of the landslide were still in active deformation with the largest LOS displacement velocity exceeding − 100 mm/year.

Highlights

Landslide disasters along highway in mountainous area are increasing progressively to constitute a majority of highway disaster events[1]
The Sunkoshi landslide is located in the northern mountainous area of Nepal with steep topography, complex geologic background and dense vegetation
The SBAS-InSAR functionality was fully implemented in the StaMPS software package, while the DS-InSAR processing chain was established in a mixed way by self-developing the preprocessing steps and adopting the spatial–temporal 3D phase unwrapping procedure embedded in StaMPS

Summary

Introduction

Landslide disasters along highway in mountainous area are increasing progressively to constitute a majority of highway disaster events[1]. It has become a great challenge for scientists and engineers of geotechnical engineering to understand and mitigate landslide hazards in mountainous areas For this purpose, the spatial–temporal evolution pattern of deformation field for a certain landslide during its life cycle should be well known. The height difference between the mountain peak and the valley floor is up to several thousand meters, forming natural steep slopes more than 30° with some part nearly vertical This area is characterized by complex geologic, hydrologic and climatic conditions, as well as frequent earthquake disasters. With the special topography of the landslide area, the surface water cannot be discharged along the surface runoff in time, but fully infiltrates along the surface cracks and loose block gravel soil layer On one hand, it makes the sliding body heavier and increases the sliding force. Rainfall caused events of landslides, debris flows and other natural disasters often happened, which seriously affected the post-disaster reconstruction and the daily life of local people

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