Study on landslip-hit locations in Kerala highlights need to research rainfall dynamics

Accurate rain forecast that allows for early warnings key to cut risks

Amidst rising concerns over the resumption of quarrying on the high ranges in and around Kottayam in Kerala, a latest study on the fatal landslips that struck Koottickal, Kokkayar and Plappally last year attribute these primarily to human interventions and high-intensity rainfall.

The study, carried out by K.S. Sajin Kumar, a member of the Kerala Landslide Expert Committee, and others in association with the Kerala State Disaster Management Authority, calls for a stringent land use policy for such landslip-prone areas. The steep slopes of all the three locations, which are located in the same valley and originally contained natural contiguous forests, are now dominated by human interventions in the form of plantations, highways and settlements.

“All agricultural techniques on the hilly slope affect the lower-order drainage by obstructing it with rubble masonry, redirecting it to a more hazardous slope. These lower-order courses, except in thickly vegetated forest areas, are usually seasonal, and during the monsoon season, the normal flow of water is disturbed by these practices,” pointed out the study.

A closer check, meanwhile, also revealed that the Kokkayar landslip was completely caused by human activities, whereas the Plappally landslip was also impacted by geomorphic and tectonic causes. The landslip at Kavali, meanwhile, was caused by forest fragmentation.

Terming the intense rainfall of 266 m on October 16, 2021 that triggered these landslips as an ‘anomalous event’ , the study emphasises that an accurate and exact rainfall forecast that allows for the issuance of early warnings based on the rain threshold of the area is essential to limit the risks. Having automated rain gauges that report rain information near-real time will be critical for developing early warning systems.

“Climate change has begun to bring more extreme rainfall events but the events are too complex and data too patchy to forecast such disasters. So the vital feature to be researched is the rainfall dynamics, which can be converted into early warning systems, thereby saving countless lives,” explained Mr. Kumar.

According to him, the establishment of a close network of Automatic Weather Stations in the hilly regions will help experts asses the soil saturation limit and threshold of rainfall from time to time and issue necessary directions to the public.