Study links increased urbanisation with heavy rainfall in southern cities

Increased urbanisation is possibly causing heavy rainfall events in the cities of Tamil Nadu, Telangana and Kerala over the past few years, according to a study conducted by a team of researchers from the University of Hyderabad (UoH).

The team, led by Karumuri Ashok, a professor with UoH’s Centre for Earth, Ocean and Atmospheric Sciences, studied whether a common factor — the changing land use land cover (LULC) in these States — has any implication for the heavy rainfall reported in South Indian cities in recent years.

Several heavy rainfall events have been reported in southern cities, including the extreme rainfall that created havoc in Chennai and nearby areas in December 2015, the heavy rain over Hyderabad and adjoining regions in September 2016, and the extreme rainfall event in Kerala in August 2018.

These three States differ in their geographical locations and the season in which they receive rainfall. The study showed that the precipitation during heavy rainfall events in these States has significantly increased from 2000 to 2017.

Using LULC data from ISRO, and by conducting 2 km resolution simulation experiments of 12 heavy rainfall events over the States, the researchers found distinct LULC changes in the States, which led to higher surface temperatures and a deeper and moist boundary layer.

These in turn caused a relatively higher convective available potential energy and, consequently, heavier rainfall, according to the study. It further stated that increasing urbanisation in Telangana and Tamil Nadu is likely to enhance rainfall during heavy rainfall events by 20-25 per cent.

The findings of the study were reported in the Quarterly Journal of Royal Meteorological Society on May 18, according to a release.