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Bengaluru, one of India鈥檚 fastest-growing cities, has witnessed an average economic growth rate of 8.5 per cent over the past decade. As a major economic hub, it hosts diverse sectors such as technology, banking, consulting, defence, and R&D. However, this rapid development has led to large-scale urbanisation and a significant population influx, severely straining the city's natural ecosystem鈥攅specially its drainage infrastructure鈥攍eading to recurring urban flooding. 

Bengaluru鈥檚 primary stormwater channels, known as Rajakaluves, were originally built to manage stormwater by connecting to the city's lakes. Over time, unplanned development has left many of these drains are outdated or damaged. According to the Central Public Health and Environmental Engineering Organisation (CPHEEO) Manual on Sewerage and Sewerage Treatment, urban stormwater drains in Indian cities are designed for rainfall intensities of just 12鈥�20 mm per hour. However, rainfall events in Bengaluru have significantly intensified. For instance, on 18th May 2025, the city experienced rainfall of 100鈥�135 mm in a single day, far exceeding the system鈥檚 design capacity. 

As Bengaluru continues to expand, sustainable urban growth demands robust upgrades to critical infrastructure鈥攑articularly stormwater drainage鈥攖o prevent escalating social and economic costs.  

One of the biggest hurdles in improving the city鈥檚 drainage system is the lack of accurate and comprehensive mapping. This limits the ability of municipal authorities to assess and plan for infrastructure upgrades. Consequently, real estate projects are often approved within drainage buffer zones, further restricting water flow and exacerbating flooding. 

To address this, innovative approaches to stormwater infrastructure are essential. Global examples show that well-designed systems can yield not just environmental but also economic and social benefits. 

Japan鈥檚 鈥淯nderground Temple鈥�, officially the Metropolitan Area Outer Underground Discharge Channel, completed in 2006, lies 50 meters below Kasukabe City. This anti-flood network consists of five massive silos linked by 6.4 km of tunnels, capturing stormwater during heavy rains and typhoons before discharging it into a nearby river. It also serves as a tourism site, with guided tours generating revenue that helps offset maintenance costs. 

Similarly, Seoul鈥檚 Cheonggyecheon Stream Restoration Project, launched in 2003, stands as a benchmark for integrated urban renewal. The initiative involved removing an elevated highway to restore a historic stream, resulting in a 639% increase in biodiversity by 2008 and a reduction in urban heat island effect by 3.3掳C to 5.9掳C. The upgraded flood protection system can now manage up to 118 mm/hour of rainfall, equivalent to a 200-year flood event. The revitalization significantly boosted the local economy in the form of increase in property values, tourism, public transit usage etc (Source: Landscape Architecture Foundation). 

Another forward-thinking approach is the 鈥渟ponge city鈥� model, prominent in Chinese cities like Shanghai and Wuhan. It combines traditional drainage with green solutions鈥攔ain gardens, permeable pavements, wetlands鈥攖o absorb rainwater and recharge groundwater. Backed by national policies and funding, this model addresses flooding, water scarcity, and ecological degradation. 

Bengaluru must adopt similar strategies. According to a 2023 Knight Frank report on Urban Flooding in Bengaluru, the city currently has 842 km of primary and secondary drains but needs an additional 658 km. Revamping the existing network鈥攖hrough desilting, dredging, and unclogging鈥攚ill also be necessary. The total cost for expansion and repair is estimated at Rs 28 billion. 

Funding can be sourced from multilateral agencies like the World Bank and Asian Development Bank (ADB). For long-term maintenance, Value Capture Financing (VCF) can help ULBs recover costs through increased land values and real estate development in protected zones. 

Bengaluru鈥檚 ability to tackle its flooding crisis will depend on how quickly and effectively it can upgrade its stormwater systems鈥攚hile learning from global best practices to build a more resilient urban future.