Kerala recorded the highest number of landslides with 2,239 landslides out of 3,782 major landslides in the country in the past 7 years, the ministry of earth sciences told the Lok Sabha on Wednesday. West Bengal recorded the second highest number of landslides with 376 landslides between 2015 and 2022.
Union minister for earth science and science and technology, Jitendra Singh, was answering a question on whether the government is paying any attention to the increasing number of landslide incidents occurring in the country in the recent past and the reasons for the rise.
Based on inputs from the ministry of mines, Geological Survey of India (GSI) collected data of 3,782 major landslides in the country during the period. For all these landslides, GSI collected preliminary geo-parametric attributes for each of the landslides, including studying its impacts, future vulnerability etc. GSI also carried out a national landslide susceptibility mapping (NLSM) since 2014-15 and prepared a 1: 50,000 scale landslide susceptibility mapping of an area of 4.3 lakh sq km in different landslide prone states. GSI also collected historical information on 8,645 landslide polygons using both remote sensing (RS) and field based source data for 29,738 landslides.
Post disaster investigations of the landslides reveal that major trigger for landslides is unprecedented high rainfall. Other important geo-factors include terrain character, slope forming material, geomorphology, land use and land-cover in different terrains etc. Anthropogenic causes such as unprotected slope cuts, blocking of drainage are also seen in many landslide analyses. The number of field validated landslides analyzed as part of NLSM since 2014-15 which uses historical landslide data shows the number of field validated landslides is highest in Himachal Pradesh, Uttarakhand and Kerala with 6,420, 4,927 and 3,016 landslides. The landslides polygons mapped are again highest in Uttarakhand, Himachal Pradesh and Arunachal Pradesh.
In response to a question on whether the country is witnessing an unusually early and active phase of the annual rainy season and whether this unusual rain pattern is not good for agriculture and calls for effective water management system, the ministry said:
“Early onset of south-west monsoon is an inherent property observed in the inter-annual variability of monsoon behaviour. This year the monsoon onset over Kerala was on May 29 against the normal date of June 1, 3 days ahead of normal date, and it covered the entire country on July 2, against the normal date of July 8 ie six days ahead of the normal date for monsoon coverage for the entire country.”
The ministry also referred to 29 reports of states and union territories (UTs) on “Observed Rainfall Variability and Changes” which have been published by the India Meteorological Department (IMD) in January 2020.
The reports suggest that 5 states, Uttar Pradesh, Bihar, West Bengal, Meghalaya and Nagaland, have shown significant decreasing trends in monsoon rainfall during the 30-year period between 1989 to 2018. The annual rainfall over these five states along with the states of Arunachal Pradesh and Himachal Pradesh also show significant decreasing trends. Other states do not show any significant changes in south-west monsoon rainfall during the same period.
Considering the district-wise rainfall, there are many districts in the country, which show significant changes in south-west monsoon and annual rainfall during the 30-year period. There is a significant increasing trend in terms of heavy rainfall days observed over Saurashtra and Kutch, south-eastern parts of Rajasthan, northern parts of Tamil Nadu, northern parts of Andhra Pradesh and adjoining areas of south-west Odisha, many parts of Chhattisgarh, south-west Madhya Pradesh, West Bengal, Manipur, Mizoram, Konkan, Goa and Uttarakhand.
“Changes in rainfall pattern may impact agriculture if it exceeds the critical limit. However, the severity of impact depends upon various factors, such as crop type and variety, location of land and type of soil, stage of crops etc. Appropriate measures during occurrence of unusual rainfall may save the crops up to a certain extent. IMD runs an operational Agrometeorological Advisory Services (AAS) viz., Gramin Krishi Mausam Sewa (GKMS) scheme for the benefit of farming community in the country,” the ministry said adding that IMD also monitors rainfall situation and weather aberrations including heavy rainfall and issues alerts, warnings for extreme weather events along with suitable remedial measures to the farmers.