A recent analysis of satellite imagery has highlighted the impact of five decades of unplanned urbanization on the severe flooding that affected north Bengaluru on October 22. The flooding, which impacted areas from Yelahanka to Ballari Road, has been attributed to the choking of natural drainage networks, as revealed by PG Diwakar, Isro Chair professor at NIAS and former Isro director (Earth Observation).
Using satellite data from India’s Cartosat-1 and Europe’s Sentinel-1, Diwakar emphasized that the flooding was exacerbated by a lack of consideration for the city’s natural water flows. He explained that the drainage network in northern Bengaluru was designed to channel rainwater from Hebbal to the Vrishabhavathi River. However, the recent heavy rains overwhelmed these streams, leading to widespread flooding.
A comparative analysis of satellite imagery from 1973 and recent data shows a stark transformation of the landscape: while the older images reveal clear drainage networks and natural water channels, the newer imagery indicates these essential waterways have been largely obscured by concrete development.
The flooding affected various areas, including Kendriya Vihar, Doddabommasandra Lake, Bagalur, and Jakkur. Due to heavy cloud cover, Diwakar relied on radar imaging, which penetrates clouds, for his analysis.
Previous studies conducted by Diwakar and geologist VR Hegde have shown that Bengaluru’s unique topography is ideally suited for natural rainwater drainage, provided it remains uninterrupted. They warned against altering this natural landscape, which could lead to further flooding issues.
To address these challenges, the researchers proposed a phased approach to flood management:
- Phase 1: Focus on Hebbal and Bellandur valleys by directing stormwater to the Ponnaiyar River and widening it to accommodate floodwaters while preserving wetlands.
- Phase 2: Protect western and southern Bengaluru, ensuring the Thippagondanahalli reservoir is shielded from pollution and declaring a buffer zone along the Vrishabhavathi River to prevent urban development.
- Phase 3: Safeguard the Kempegowda International Airport area from becoming like east Bengaluru, emphasizing timely protective measures due to ongoing development pressures.
This analysis serves as a critical reminder of the importance of sustainable urban planning in mitigating flooding risks in Bengaluru.
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