Bengaluru's Flooding Crisis: Unplanned Urbanization and Natural Drainage Systems at Risk

BENGALURU: A recent analysis of satellite imagery reveals that decades of unplanned urbanization have significantly contributed to the severe flooding experienced in North Bengaluru on October 22, 2024. The flooding, which affected areas from Yelahanka to Ballari Road, was attributed primarily to the obstruction of natural drainage networks. PG Diwakar, an Isro Chair Professor at the National Institute of Advanced Studies (NIAS) and former Isro Director of Earth Observation, highlighted that the city’s development has largely ignored its natural water flows.

Diwakar analyzed satellite data from India’s Cartosat-1 and Europe’s Sentinel-1, noting that the drainage network in North Bengaluru is designed to channel water west-east towards the Vrushabhavathi River. However, heavy rains on October 22 caused widespread flooding due to the choking of these vital streams, which are supposed to facilitate drainage from Hebbal towards the river.

A comparative review of historical imagery from 1973 and recent satellite data shows a stark transformation: while the 1973 images depicted clear drainage channels, modern imagery reveals that these waterways have been largely paved over by concrete and construction. Areas significantly impacted by the flooding include Kendriya Vihar, Yelahanka, Doddabommasandra Lake area, Kogilu, Bagalur, Ballari Road (Airport Road), Doddaballapur Road, Jakkur, and Byatarayanapura.

Diwakar used advanced radar imaging from the Sentinel-1 satellite to capture data on October 24, which showed extensive waterlogging in northern Bengaluru. The radar images revealed dark green patches indicating accumulated water and moisture retention, underscoring the consequences of neglecting natural topography. “When heavy rains hit, water had no designated path to follow, leading to flooding in low-lying areas,” he explained, emphasizing that dense urban settlements around Doddabommasandra and Hebbal lakes have blocked traditional water passages.

In previous reports, Diwakar and geologist VR Hegde detailed how Bengaluru’s unique topography allows for natural rainwater drainage if left undisturbed. Their research identified a need for immediate solutions to prevent North Bengaluru from experiencing the same flooding issues as East Bengaluru. Proposed solutions are categorized into phases:

Phase 1: Address issues in the Hebbal and Bellandur Valleys by directing stormwater to the Ponnaiyar River, widening the river to accommodate floodwaters, and protecting undeveloped wetlands and green areas.
Phase 2: Safeguard western and southern Bengaluru by protecting the Thippagondanahalli Reservoir from sewage and chemical waste, and designating buffer zones along the Vrishabhavathi River and Suvarnamukhi as “No Development Zones.”
Phase 3: Prevent the Kempegowda International Airport (KIA) area from becoming like East Bengaluru, as it is a focal point for many developments, making timely intervention crucial.

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