Everyone monsoonThis pattern is repeated throughout the city.Roads disappear under water, traffic stops, etc.RainThere are delays and water has entered residential colonies, offices, parks, schools and hospitals. Potholes become hard to spot, drains overflow and even a few hours of heavy rain can disrupt daily life.Excessive rainfall and inadequate drainage are often blamed. But researchers and government agencies have increasingly pointed to another factor: the rapid concretization of urban spaces.As cities expand, open land, wetlands, and vegetation are replaced by buildings, roads, sidewalks, and parking areas made of concrete, asphalt, and other impermeable materials. Due to this, the capacity of soil to absorb rain water reduces.Water that once seeped into the ground and recharged aquifers quickly flows over hard surfaces and enters storm water drains. During intense monsoon periods, the amount of runoff can exceed the capacity of these drains, causing waterlogging and urban flooding.
When concrete turns rainfall into runoff
Urban flooding is no longer seen solely as the result of unusually heavy rainfall. Studies have linked this to the way cities expand, often at the expense of lakes, wetlands, vegetation and open soil.Uncontrolled construction, encroachment on water bodies and widespread cementation have altered the natural flow of water through the urban landscape. Impermeable surfaces increase the speed and volume of runoff, while the destruction of lakes and wetlands reduces the space available for storing excess rainwater.The result is that even when cities add more drains, water can reach them faster than the system is equipped to carry it away.
Bengaluru: Less vegetation, fewer lakes and faster runoff
A 2017 study by the Center for Ecology at the Indian Institute of Science found that Bengaluru’s urban area has expanded by more than 1,000 percent since the 1970s. Over the same period, vegetation cover declined by approximately 88 percent and water bodies declined by approximately 79 percent.The study estimated that about 78 percent of Bengaluru’s surface has become impervious, leaving limited space for rainwater to seep into the soil.
Bengaluru’s concrete crisis
Rainfall that previously recharged groundwater now flows over concrete and asphalt into stormwater drains, increasing both the volume and velocity of surface runoff.The researchers also examined the impact of concrete-lined drains. Such drains can carry water faster than channels lined with soil and vegetation. But concrete prevents infiltration and reduces surface friction, allowing large amounts of water to reach low-lying areas in a short period of time.According to the study, this approach could shift flood risk from one part of the city to another rather than addressing it.The researchers also found that the traditional Rajakaluve storm water channel connecting the City Market to Bellandur Lake had narrowed from about 60 meters to 28.5 meters due to encroachment and physical changes.The findings were later cited in the Comptroller and Auditor General’s September 2021 performance audit on stormwater management in Bengaluru.The CAG found several lapses in the city’s stormwater management, including discrepancies in the reported length of drains and the lack of a complete list of tertiary drains.The audit also documented the degradation of Bengaluru’s water bodies. In the city’s current 741 square kilometer area, their numbers fell from 1,452 in the early 1800s to 194 in 2016.Their combined storage capacity reduced from about 35 thousand million cubic feet or about 991 billion liters to about 5 thousand million cubic feet or about 142 billion litres.This loss of storage capacity has left the city with fewer natural places to store excess monsoon water.
Delhi: River flooding and local waterlogging
Similar concerns were raised in the report of the National Disaster Management Institute. Yamunaurban flooding In Delhi with a focus on organizing the event in July 2023..According to the report, Delhi’s urban land cover increased from 46.2 percent in 1991 to 75.1 percent in 2011. Separately mapped built-up area increased from about 20 percent in 1985 to more than 52 percent by 2018.
Delhi’s concrete footprint
NIDM said the increase in impervious surfaces has reduced the time taken by rainwater to reach drains and the Yamuna. This produced higher peak flows and increased the potential for flash flooding, including periods of rain that might not otherwise cause widespread disruption.The report differentiates between the two forms of flooding in the capital.The first occurs when high water levels in the Yamuna push river water back into Delhi’s drainage network. The second is local urban flooding, in which runoff from roads, footpaths, colonies and other built-up areas enters the drains faster than they carry it away.NIDM identified concretization, pressure on drainage infrastructure and encroachment on the Yamuna floodplain as factors that could aggravate the July 2023 flood.
Mumbai: Flood mitigation along with expansion of concrete cover
In Mumbai, flood-control expenditure has increased, but so has the city’s built-up area.The Brihanmumbai Municipal Corporation had invested in river rejuvenation, pumping stations, hazard mapping and weather forecasting as part of its flood-mitigation measures.At the same time, redevelopment and infrastructure projects continued to add impervious surfaces across the city.About 38 per cent of the BMC’s annual budget was set aside for climate-related measures, including a large portion for flood and water management.However, redevelopment projects were expected to add about 344 million square feet of built-up area. Officials quoted in the report said construction and redevelopment are proceeding faster than flood-mitigation and environmental-restoration measures.
Mumbai’s development versus climate paradox
Mumbai has also undertaken extensive concretisation of roads as a response to potholes and poor road conditions. While concrete roads can provide greater durability, expanding hard surfaces without adequate water-absorption measures can increase stormwater runoff.The BMC’s climate budget report for 2026-27 has provided an allocation of about Rs 48,164 crore, of which 43 per cent has been earmarked for five climate-related risks, including urban flooding.
What instructions has NGT given?
In an order dated May 21, 2025, the National Green Tribunal issued directions to local bodies and development authorities across India against indiscriminate concreting and construction of roads, berms and footpaths during urban development.The tribunal called for the use of permeable or semi-permeable surfaces and directed officials to preserve non-concrete space around trees.It said the Uttar Pradesh government order dated March 23, 2018, should serve as the default guideline for those states and union territories that have not made their own rules.The guidelines recommend permeable paving instead of continuous concrete surfaces, ban on paving around lakes, ponds, parks and roadside green areas and a minimum one meter de-concrete area around trees.They also demand rainwater-harvesting systems in larger developments and groundwater-recharge structures including ponds and recharge pits in new layouts.
Cities begin de-concretization efforts
Some municipal authorities have begun implementing measures aimed at restoring open soils and protecting water bodies.Ahead of World Environment Day in 2025, Bengaluru ordered removal of concrete, cement and stone blocks within a one-metre radius of roadside trees.The city has also used drone surveys, geographic information system mapping and digital lake records to support the drive to identify and remove encroachments.In 2024, the Municipal Corporation of Delhi said it has deconcreted the area around 24,000 of the approximately 41,000 trees identified in its jurisdiction.The Delhi Development Authority has also launched a demolition drive against unauthorized structures on the Yamuna floodplain following directions from the Delhi High Court and the NGT.However, such measures are limited compared to the pace at which Indian cities continue to build roads, housing projects, commercial complexes and other infrastructure.
More drains alone may not be enough
Concrete remains central to urban construction because it is durable, widely available and able to withstand heavy loads. It can be molded into various forms and does not burn, rot or rust.The challenge is not to eliminate concrete altogether, but to avoid using it where permeable alternatives are possible.The NGT has recommended materials such as stabilized soil, coarse sand, fly-ash bricks, stones and perforated tiles for walkways and open areas. These materials allow at least some rainwater to penetrate into the ground.Where concrete cannot be avoided, measures such as bioswales, rain gardens, recharge pits and soak pits can be incorporated into roads and drainage systems. These structures slow the flow of water and allow some of it to seep into the soil instead of sending the entire amount directly down the drain.Urban flooding cannot be dealt with simply by widening drains or installing more pumps while the surrounding landscape becomes harsher.As monsoon rainfall becomes more difficult to manage, cities will also have to rethink how their roads, sidewalks, open spaces and neighborhoods are designed. Restoring wetlands, protecting drains and floodplains, and creating more permeable surfaces will be just as important as building new drainage infrastructure.
