Geophysical investigation to improve the landslide susceptibility analysis in Kerala, India.

During 1–20 August 2018 the southern state of Kerala in India experienced 140% more rainfall than normal. This extreme event demonstrated the vulnerability of Kerala’s population to landslides and flooding, claiming 483 human lives and displacing more than one million people. More than 1,300 landslides affected numerous bridges and roads, cutting off towns, villages, and livelihoods of communities. Idukki district in Kerala is an area of 4150 sq. km. with a population of 1.1 million and was the worst hit by landslides. Immediately after the 2018 rainfall event, Dr. Thomas Oommen, Project Lead (PI) was tasked by the National Science Foundation (NSF) to lead a reconnaissance survey in Kerala. The survey identified critical data gaps, including the lack of rain gauge networks and landslide hazard nowcasting systems to provide warning to communities in such life-threatening events.

This GWB project started in early 2020 as follow-up from the PI’s 2018 survey. A field survey of geotechnical properties, initially scheduled for the summer of 2020, had to be postponed due to Covid-19. Use of satellite products to aid the study was proposed instead for which Global Precipitation Mission (GPM) satellite rainfall product was deemed useful. The team developed a methodology for calibrating data with respect to rain gauge observations and also employed a resolution improvement technique. Further research to improve this technique is undergoing. Efforts to increase the rain gauge network in the study area led to identifying 10 optimal locations for installation in early 2021. This extended network would provide robust rainfall input for the landslide forecasting model. The geophysical survey is scheduled for the summer 2021 with two phases: one before the onset of the monsoon and one during the monsoon at the project location.

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