Flood 2018 and the status of reservoir-induced seismicity in Kerala, India

Floods in India, which were once mostly confined to southern part of the Himalayan region, have now started spreading over to many regions of India, including the urban conglomerations and the desert tracts of Rajasthan too. The flood that occurred in Kerala during August 2018 is one such major disaster that caused huge damages to man, infrastructure and properties, estimated to the worth of 200 billion USD. Besides, they are expected to cause a chain of other hazards, and one among these is reservoir-induced seismicity (RIS). The RIS occurs in deep reservoirs with high water column. While the water column increases the total stress on the earth crust, the infiltration causes pore pressure increase which in turn decreases the effective strength of the earth crust. Such changes in the stress regime cause RIS (earthquake). The rocks of the Western Ghat Mountains of Kerala are highly deformed with folds and faults of Archean/Precambrian tectonics and have undergone morphological modifications during Pleistocene tectonics. The region is also seismically active. Further, the Western Ghats cover vast area in Kerala; almost all the dams and reservoirs are located in the highly folded, fractured, faulted and along the deep valleys of the Western Ghats. In the context of recent August 2018 flood disaster, the probability of RIS has increased. So, GIS analysis was carried out using various geosystems, seismicity, distribution of dams, zones of heavy rainfall 2018 and the flood inundation, which indicates that 50% of the reservoirs are highly prone to RIS. The RIS would have occurred during August 2018 flood itself, but for the release of water from the overflowing reservoirs. However, owing to the proneness of the region to RIS, optimal water management is necessary for the dams and reservoirs of Kerala.