21-05-2025
Bengaluru floods: Can the tech capital draw lessons from China's sponge cities and Japan's flood tunnels?
With Bengaluru grappling with frequent flooding, there's a growing consensus that conventional drainage solutions are no longer enough. Cities around the world are turning to innovative, integrated stormwater infrastructure that not only controls floods but also delivers environmental, economic, and social benefits.
From Japan's colossal underground flood chambers to China's nature-based 'sponge city' model, global examples offer valuable insights Bengaluru can draw from to build a more resilient and sustainable urban future, an analysis by Knight Frank India has said.
Bengaluru has recorded an average economic growth rate of 8.5% over the past decade. As a thriving hub for technology, banking, consulting, defence, and R&D, the city continues to attract significant investment and talent. However, this rapid urbanisation and population surge have placed immense pressure on its natural ecosystems, particularly its drainage infrastructure, resulting in frequent urban flooding, it noted.
'One of the biggest hurdles in improving the city's 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,' said Shilpashree Venkatesh, Assistant Vice President – Research, Knight Frank India.
Bengaluru's ability to tackle its flooding crisis will depend on how quickly and effectively it can upgrade its stormwater systems—while learning from global best practices to build a more resilient urban future, she said.
To tackle this growing challenge, Bengaluru must adopt innovative stormwater management strategies. The consultancy noted that global examples demonstrate that well-designed, integrated systems can deliver not only environmental benefits but also economic and social gains.
Japan's 'Underground Temple', 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, said Knight Frank India.
Seoul's 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°C to 5.9°C. The upgraded flood protection system can now manage up to 118 mm/hour of rainfall, equivalent to a 200-year flood event. The revitalisation significantly boosted the local economy in the form of an increase in property values, tourism, public transit usage, it noted.
Another forward-thinking approach is the 'sponge city' model, prominent in Chinese cities like Shanghai and Wuhan. It combines traditional drainage with green solutions—rain gardens, permeable pavements, wetlands—to absorb rainwater and recharge groundwater. Backed by national policies and funding, this model addresses flooding, water scarcity, and ecological degradation, it said.
