On 28 June 2024, Delhi received 228.1 mm of rain in 24 hours, more than its average for the entire month of June and its highest June-day total in 88 years. Four months later, Bengaluru recorded 186 mm in a day, its highest since 1997. In September 2025, Kolkata received 251.6 mm in 24 hours, its heaviest rain since 1988. Streets flooded, transport stalled and at least 12 people died. (Source: Reuters on Delhi, Bengaluru and Kolkata)
Different cities, but a familiar picture with submerged vehicles, flooded homes and overwhelmed drainage systems. The rain was extreme, but it met cities where soil had been paved, water bodies had shrunk and natural channels had been built over.
Can cities continue trying to drain every drop away, or must they make room for water?
Why has urban flooding become a recurring city crisis?
Urban flooding happens when rain enters a built-up area faster than the ground, water bodies and drainage network can absorb, store or carry it. Unlike river flooding, it can occur far from a river. One intense cloudburst over a densely paved neighbourhood may be enough.
Urbanisation changes every raindrop’s route. Natural ground, vegetation and ponds intercept or absorb rain. Roads, rooftops and parking areas turn it into fast-moving runoff.
The National Disaster Management Authority estimates that urbanisation can increase flood peaks by 1.8 to eight times and flood volumes by up to six times. The same rain therefore produces a faster, larger surge after a catchment is built over. (Source: NDMA’s Guidelines on Management of Urban Flooding)
Several environmental challenges deepen the problem:
- Intense rainfall – A warmer atmosphere can hold more moisture, supporting heavier downpours.
- Unplanned land use – Building on wetlands, floodplains and natural drains removes safe storage.
- Too much concrete –Paved surfaces reduce infiltration and accelerate runoff.
- Weak drainage systems – Undersized, disconnected or blocked drains cannot carry peak flow.
- Solid waste – Plastic, silt and debris reduce drain capacity.
- Groundwater depletion – Cities pump water from below while preventing rain from recharging aquifers.
Climate patterns also influence rainfall, but they need careful explanation. The El Nino effect can alter the Indian monsoon, although the India Meteorological Department stresses that this relationship is not automatic; the Indian Ocean Dipole and other atmospheric conditions also matter.
Similarly, glacier melting threatens Himalayan water systems but does not explain a flooded Bengaluru underpass. It can increase glacial-lake hazards in mountain regions; routine city waterlogging usually comes from intense rain, impermeable surfaces and inadequate drainage.
The urban flooding problem is becoming expensive
Urban floods interrupt work, schools, hospitals and transport. They damage homes, vehicles and small businesses, particularly for uninsured families.
A 2025 World Bank assessment estimated that urban flooding already causes around $4 billion in annual losses in India. Without stronger action, that could reach $30 billion a year by 2070. India’s urban population could reach 951 million by 2050, making climate resilience a mainstream investment need. (Source: World Bank findings reported by Reuters)
Bengaluru offers a stark warning. Research cited by Reuters found that the city lost 88% of its green cover over four decades while its concretised area increased elevenfold. More than 85% was assessed as vulnerable to flooding. Encroachment, waste and fragmented development weakened its network of lakes and connecting drains.
This is why better stormwater management cannot begin and end with another pipe.
Why are bigger drains not enough?
Drains, culverts and pumps remain essential, but they have fixed capacity. When rain enters faster than they can discharge it, streets become storage areas. A larger pipe may simply transfer flooding downstream when the receiving water body is full.
The stronger approach combines three layers:
- Grey infrastructure –Drains, pipes, pumps, culverts and barriers
- Blue infrastructure – Lakes, ponds, rivers, wetlands and restored floodplains
- Green infrastructure – Trees, soil, parks, rain gardens, bioswales and green roofs
Together, they form more resilient drainage solutions. Grey infrastructure moves water; blue and green infrastructure hold, absorb and slow it. The aim is to reduce the sudden peak that overwhelms the city.
What are nature-based solutions?
Nature based solutions protect, restore or imitate natural processes to address social and environmental problems. In flood management, they use soil, vegetation and water bodies to intercept rain, increase infiltration, provide temporary storage and release water more slowly.
This means more than planting trees. Effective nature-based solutions require hydrological data, safe overflows, water-quality controls and maintenance. A rain garden in unsuitable soil or a lake with a blocked inlet cannot perform properly.
The “sponge city” idea applies the same logic across an urban catchment: allow buildings, streets, parks and water bodies to absorb or detain more rain close to where it falls.
Green infrastructure solutions that Indian cities can use
Solution | Flood-management role | Where it can work | Wider value |
Restored wetlands | Stores water and releases it gradually | Floodplains and low-lying areas | Habitat and water treatment |
Reconnected lakes | Adds storage across a catchment | Existing urban lake systems | Groundwater recharge |
Sponge parks | Temporarily holds excess rain | Parks, playgrounds and public land | Recreation and cooling |
Permeable paving | Allows water to pass through | Footpaths, courtyards and low-traffic areas | Lower surface runoff |
Green roofs | Retains part of rooftop rainfall | Homes and commercial buildings | Insulation and cooling |
Urban forests | Intercept rain and improve soil absorption | Public land and river corridors | Shade and biodiversity |
Detention ponds | Holds runoff during peak rain | Campuses and new developments | Irrigation storage |
Rainwater harvesting | Stores or recharges relatively clean roof water | Buildings and institutions | Better water security |
No intervention works in isolation. Ten rain gardens cannot compensate for a filled wetland. A sustainable building needs more than a token recharge pit; its roof drainage, storage and overflow must work together. The same principle applies citywide.
What can India learn from projects already underway?
Chennai - Turning parks into temporary sponges
The Greater Chennai Corporation is developing sponge parks that retain rain and allow some to enter the soil. Excess water flows towards the nearest stormwater drain, reducing the immediate load. Chennai’s 2025–26 climate budget recorded further work as ongoing. (Source: Greater Chennai Corporation and its Climate Budget)
The real test is performance, in terms of storage, drainage time and reduced waterlogging. Publishing these results would distinguish flood infrastructure from decorative landscaping.
Bengaluru - Rebuilding the relationship between lakes and the city
In June 2025, the World Bank approved a $426 million programme intended to improve water security for more than four million Bengaluru residents. Plans include reviving 183 lakes, building nine sewage-treatment plants, reusing treated water and strengthening flood modelling.
These are commitments, not completed outcomes. Yet the design matters: a lake cannot manage floods if sewage fills it, feeder channels are blocked or its overflow ends in a built-up area.
Kolkata - Protecting infrastructure that nature already built
The East Kolkata Wetlands show what existing natural infrastructure can do. About 260 sewage-fed fishponds, salt marshes and settling ponds process roughly 910 million litres of untreated wastewater daily while supporting livelihoods, groundwater recharge and flood moderation. The September 2025 flood exposed Kolkata’s vulnerability. The wetlands cannot prevent every flood, but fragmenting them would weaken a valuable natural buffer.
In 2024, the Union government approved roughly $300 million for flood mitigation and water conservation across seven cities. The programme includes expanding water bodies, improving drainage and developing early warnings. (Source: Reuters)
What are cities elsewhere doing differently?
Rotterdam’s Benthemplein water square functions as a public space in dry weather and can hold around 1,700 cubic metres of stormwater during heavy rain. Singapore transformed a concrete section of the Kallang River into a naturalised river and floodplain through Bishan–Ang Mo Kio Park. Bangkok’s Benjakitti Forest Park can retain up to 200,000 cubic metres of monsoon stormwater.
These examples cannot be copied into India. Rainfall, soil, density and maintenance capacity differ. The lesson is that public spaces should perform more than one job.
Can flood management also reduce urban heat?
Yes. Many measures that reduce flooding also reduce the urban heat island effect. Trees provide shade, vegetation releases moisture through evapotranspiration, and water bodies can cool their surroundings. The same green infrastructure can therefore address two growing city risks: intense rainfall and extreme heat.
The urban heat island develops when concrete, asphalt and buildings retain more heat than natural surfaces. Replacing every open plot with hard paving worsens both runoff and heat. Creating connected tree cover, wetlands, planted streets and open soil supports green cities, public health and environmental sustainability while improving flood protection.
That is the practical strength of nature-based planning. One well-designed wetland park can provide stormwater storage, shade, habitat, cleaner water and recreation. It helps build sustainable cities without requiring separate land for every benefit.
What must cities do next?
First, map the entire catchment, not only the flooded road. Agencies must know where rain falls, moves, collects and safely overflows.
Second, enforce land use rules. A floodplain cannot work after it is covered with housing. Wetlands need protected boundaries, functioning inlets and freedom from dumping.
Third, connect nature-based measures with drainage systems and provide overflow routes for storms beyond their capacity.
Fourth, measure storage, runoff, flood depth, clearance time, groundwater and water quality. Judge projects by performance during rain, not their appearance.
Finally, fund maintenance. Permeable paving clogs, wetlands collect waste and drains fill with silt. Without care, capacity declines.
Can nature-based solutions help Indian cities beat urban flooding?
Yes, nature-based solutions can help Indian cities reduce urban flooding. Wetlands, restored lakes, rain gardens, urban forests, green roofs and sponge parks can absorb, store and slow rainwater before it overwhelms drains. They are not substitutes for conventional infrastructure, but they can make the entire stormwater network work better.
Nature cannot prevent every flood. An exceptionally intense storm may exceed the combined capacity of wetlands, parks and drains. Dense neighbourhoods may have little open land. Recharge may be unsuitable where groundwater is already high or runoff is contaminated.
That does not make nature-based measures ineffective. It means cities need layered protection: forecasting, warnings, solid-waste management, resilient utilities, functional pumps, conventional drains, safe overflow routes and natural storage. Good stormwater management is a system, not a showcase project.
They can make a meaningful difference, provided cities treat them as infrastructure rather than beautification. India cannot control an extreme cloudburst, but it can influence what happens next. Rain can rush from roof to overloaded drain, or move through planned storage, absorption, reuse and discharge.
That shift connects flood protection with groundwater depletion, water security in India, heat reduction and climate resilience. Sustainable cities do not simply push water away; they give it somewhere safe to go.
Flosenso helps create resilient cities and responsible homes
City-scale urban flooding requires public planning and infrastructure. Households cannot solve it by themselves, and a home water device should never be presented as a flood-control system.
Households can still improve the way they manage stored water. Flosenso helps users monitor overhead-tank levels and automate pump operation. By stopping a pump when the tank is full, it reduces avoidable overflow, supports [smart household water management] and encourages more responsible everyday water use. It is a small household action within the much larger goal of water security.
Frequently Asked Questions
What are nature based solutions for urban flooding?
They use soil, vegetation and wetlands to absorb, store, filter and slow rain. Examples include sponge parks, rain gardens, restored lakes and green roofs.
Can green infrastructure replace city drains?
No. Green infrastructure delays runoff; drains and pumps move excess water. Cities need both during extreme rain.
How do wetlands prevent urban flooding?
Wetlands store excess water and release it gradually, reducing the flood peak reaching downstream neighbourhoods and drains.
Can rainwater harvesting reduce waterlogging?
Properly designed [rainwater harvesting] captures clean rooftop rain and reduces local runoff. Results depend on storage, soil, groundwater, maintenance and safe overflow.
Does glacier melting cause floods in Indian cities?
Glacier melting can affect river flows and glacial-lake hazards in Himalayan regions. It does not cause routine city waterlogging.
What is the difference between drainage solutions and stormwater management?
Drainage solutions carry water away. Stormwater management also decides where rain can be captured, stored, absorbed, reused and safely released.
