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A depression over the Bay of Bengal triggered the heavy rains that wreaked havoc across Andhra Pradesh and Telangana, causing widespread flooding and claiming 33 lives so far.
These rains were driven by a land-based cyclone, which drew moisture from both the Arabian Sea and land-based heat from the eastern parts of the country, according to India Meteorological Department (IMD). The combination of these factors led to Andhra Pradesh witnessing an astonishing 520 millimetres of rain in just 24 hours.
The rainfall began on August 30 and intensified through September 3, with Andhra Pradesh experiencing the brunt of this deluge. Over 27 per cent of the state’s annual rainfall occurred in just 48 hours, causing severe flooding in many areas.
Low-pressure systems formed during the monsoon are known as monsoon lows, which can further intensify into monsoon depression.
“The IMD has issued heavy rain alerts for four districts in Telangana — Adilabad, Bhadradri Kothagudem, Khammam and Mahabubabad — for September 5. Thunderstorms with lightning and strong winds are expected in isolated areas in these districts,” independent weather blogger Pradeep John told this reporter.
“Monsoon lows/depressions during the southwest monsoon are known to sustain without weakening with constant moisture flow. These low-pressure areas move slowly and dump huge volumes of rainfall in a short period. Be it the Gujarat monsoon depression in the last week or the one that created havoc in Andhra or Telangana, the pattern is the same. Some places in Gujarat or Telangana got 500 mm in 24 hours,” John said.
The next monsoon low is expected to form around September 9 and move inland via West Bengal. This system is also expected to bring heavy rainfall to eastern and central Indian states after September 10. Such extreme rainfall is typical along the path of monsoon lows, whether in Gujarat, Telangana or the one anticipated next week.
Telangana Chief Minister Revanth Reddy has directed district collectors to clear encroachments along waterbodies to prevent further flooding. He has also called for the implementation of a system similar to the Hyderabad Disaster Response and Asset Protection Agency to protect against encroachments and mitigate flooding risks.
Satellite data has revealed the extent of the devastation, with vast areas submerged and critical infrastructure damaged. Images captured by European Space Agency’s Sentinel-1 satellite showed extensive flooding across several districts on September 1, 2024. Remote sensing data highlighted submerged areas in Khammam, Mahabubnagar and Suryapet in Telangana, as well as Guntur, Krishna and Vijayawada in Andhra Pradesh.
Andhra's Guntur has been particularly hard-hit, with the southern, southeastern, northern and northwestern parts of the district suffering the most severe flooding. The situation turned tragic in Uppalapadu, where a man and his two children were fatally swept away by an overflowing lake.
In Telangana, Wyra river and Madhira lake overflowed, exacerbating the flooding in the Khammam district. Emergency services, including 38 National Disaster Response Force (NDRF) teams, have been mobilised to rescue and provide relief to affected residents. Thousands have been evacuated to relief camps as roads, bridges and railways have been severely damaged, including a key bridge near Garikapadu, which connects Andhra Pradesh and Telangana.
Further compounding the disaster, heavy inflows caused breaches in the Sitarama project’s main canal and the Peddavagu irrigation project, leading to further flooding in agricultural areas. This canal, recently inaugurated by Reddy, saw about 40-50 feet of its bund washed away.
The depression over East Vidarbha and adjoining Telangana continues to influence the region’s weather. Moving northwest at 8 kilometres per hour, it was centred over East Vidarbha at 8.30 am on September 3, 2024. It is expected to weaken into a well-marked low-pressure area, though heavy rainfall is still likely in isolated parts of Telangana, including Adilabad, Komaram Bheem Asifabad, Nirmal, Nizamabad, Jagtial, Sangareddy, Medak and Kamareddy.
Urban planners and environmentalists have raised concerns over faulty infrastructure and urban development, which have exacerbated the flooding. Poor stormwater management, rampant concretisation and inadequate rainwater harvesting systems have made cities more vulnerable to such extreme weather events.
“Rainwater has no place to percolate into the land, as every inch of the road is metalled or lined with concrete or tiles, leaving no place for the earth to take in water. Many cities in the country do not have municipal by-laws directing the developers to reserve a certain percentage of the land exclusively for the rainwater to enter the earth,” said secretary of National Environment Care Foundation (NECF) Shashidhar Shetty.
NECF has repeatedly petitioned local governments across the country to include such clauses in city planning by-laws; but the strong lobbying by developers has prevented it from becoming a widespread practice, Shetty added.
Scientists from the National Institute of Technology in Mangalore and oceanographers in Goa have also linked the large volume of rainfall in Andhra Pradesh and Telangana to land-generated heat on one side and coastal moisture circulation on the other, creating low-level land-based cyclones that draw winds from the Bay of Bengal.