Kerala reports surge in days of heavy to extremely heavy rain

New Delhi: There has been an increase in heavy rainfall events in recent decades over Kerala and the worrisome part is that these incidences are occurring not just during the southwest monsoon but also the northwest monsoon months, making it nearly 10 months in a year, India Meteorological Department (IMD) data said.

The IMD has said 2018 recorded the highest number of heavy rainfall incidences during the last five years. The devastating 2018 floods had put Kerala on the edge with similar extremely heavy rainfall incidences in 2019 and later, too, making the citizens jittery.

The total incidences of heavy rain (64.5-115.5 mm per day) in 2015 were 360 across 10 months with a maximum in June (116) followed by July (61). In 2016, the total incidences were 225 with a maximum 108 in June followed by 44 in July. The year 2017 again saw heavy rain incidences climbing to 360 with maximum 114 in June followed by 98 in September and August, too, witnessing 48 instances.

In 2018, the number of heavy rainfall events increased to 607 with July recording the maximum (198), followed by June (147) and August (144). In 2019, the total number of heavy rainfall events was 528 with 184 of them recorded in August alone, followed by 123 in July and 101 in October.

Year 2020 saw 484 incidences of heavy rainfall, in which August recorded the maximum (132), followed by September (124) while in 2021, there were a total 574 such events with maximum recorded in May (130) followed by October (112 days) and July 107 days.

In case of very heavy rainfall (115.6 to 204.4 mm per day), not just the total number of days per year has been increasing but the incidences are spread over all monsoon months too. The year 2015 registered a total 43 days, of which 19 were in June; year 2016 registered 23, of which 16 alone were in June again; year 2017 registered 38 such days with September witnessing 14 days of very heavy rainfall.

The year 2018 registered 163 such days with three months showing a double digit number of days with very heavy rainfall: August (74), June (35) and June (34). Next year, in 2019, it was 117 days spread over August (71) and July (22). In the year 2020, the total days were 110 with 40 of them in August, followed by 26 in September and 20 in July. The year 2021 recorded 115 days of very heavy rainfall, of which 51 alone were recorded in May that year.

In case of extremely heavy rainfall (more than 204.4 mm per day), while the years 2015 and 2016 witnessed only one day each; the year 2017 saw two days, one each in September and December. The year 2018 witnessed 32 such days with 25 alone in August followed by 2019, which witnessed 33 such days and 29 alone in August. The number of days when there was extremely heavy rain in 2020 were eight and in 2021, it was 11.

The information was provided by IMD in a written reply to Congress Lok Sabha member from Thiruvananthapuram, Shashi Tharoor, who asked if the Ministry of Earth Sciences (MoES) had conducted any study on the water holding capacity of soil in different regions of Kerala.

The Minister of State for Earth Sciences, Jitendra Singh said his Ministry has not conducted any study on the water holding capacity of soils of Kerala.

“However, the Kerala government had published various information on Kerala soils,” he said and provided the link to that online portal.

The Union Minister, however, said the MoES did not recommend procedures for improving the water holding capacity of soil in Kerala as the state landslides mainly fall under the type “debris flow”, which occurs due to intense rainfall causing loose soil, boulders and rock pieces to slide along steep slopes.

“Therefore, the safe and quick passage of surface water through drainage channels without any blockage is preferred rather than increasing the water holding capacity of soil strata of the slopes. The enhanced water retention in slopes increases the weight of overburden, which promotes occurrence of landslides,” Singh said in a written reply.

The Union Minister also carried two maps for rainfall events over various districts of Kerala for the decade 2001 to 2010 and 2011 to 2020 respectively, which made it clear that there is an increase in heavy rainfall events in recent decades over Kerala.

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