Why Indian cities flood after heavy rain and overheat in summer

Why in the News

A 2025 amendment to Section 41A of the Disaster Management Act, 2005 has created Urban Disaster Management Authorities, a governance response to the recurring pattern of Indian cities flooding after heavy rain and overheating in summer. World Bank cost estimates on urban flood damage and a NITI Aayog assessment of the gap between master-plan provisions and their actual implementation frame the same underlying problem: cities are being planned for climate conditions they no longer experience, and the governance structures meant to close that gap have themselves lagged.

Why do Indian cities flood after heavy rainfall?

1. Unplanned urbanisation over natural drainage channels: Rapid, often unauthorised urban expansion has built over natural drainage channels, lakes, and wetlands that previously absorbed and carried away excess rainwater, removing the city’s own natural flood buffer.
2. Storm-water drainage systems designed for outdated rainfall intensity: Much of urban India’s storm-water drainage infrastructure was designed decades ago for rainfall intensities lower than what cities now experience during concentrated, high-intensity rain events.
3. Impervious surface cover reduces natural absorption: The replacement of open, permeable ground with concrete and asphalt across expanding cities means a much larger share of rainfall runs off immediately rather than being absorbed into the soil, overwhelming drainage systems built for lower runoff volumes.
4. Fragmented civic responsibility for drainage maintenance: Responsibility for different components of urban drainage, roads, sewers, and stormwater channels, is often split across separate municipal, water-board, and public-works departments, leaving no single body accountable for the full drainage system’s maintenance.

Why do the same cities overheat in summer?

1. Loss of urban green cover and water bodies: The same unplanned urbanisation that removes natural drainage also removes the tree cover and water bodies that moderate local temperature, contributing to the urban heat island effect, the pattern by which built-up urban areas run measurably hotter than surrounding rural areas due to concrete and asphalt absorbing and re-radiating heat.
2. Building density without ventilation planning: Dense, closely packed construction without adequate spacing or ventilation corridors traps heat at street level and limits the natural air movement that would otherwise help dissipate it.
3. Overheating and flooding share the same root cause: Both problems stem from urban master plans that have not kept pace with the density and climate conditions cities actually face, meaning a plan built around outdated rainfall and temperature assumptions fails on both fronts simultaneously.

What does the Section 41A amendment change?

1. Creates dedicated Urban Disaster Management Authorities: The 2025 amendment to Section 41A of the Disaster Management Act, 2005 mandates the creation of Urban Disaster Management Authorities specifically for cities, distinct from the district-level disaster management authorities the original 2005 Act established.
2. Intended to close the urban-specific governance gap: The amendment responds to the recognition that urban flooding and heat risks require a governance structure focused specifically on city-level infrastructure and planning, rather than being folded into a district authority that also covers rural areas with different risk profiles.
3. Implementation still depends on State-level rules: Like other provisions of the Disaster Management Act, 2005, the practical functioning of Urban Disaster Management Authorities depends on rules and staffing decisions each State government must still put in place.

What is the scale of the cost, and the implementation gap?

1. World Bank cost estimates on urban flood damage: World Bank assessments have placed a substantial recurring economic cost on urban flood damage in India each year, covering infrastructure repair, business disruption, and health impacts, a cost that provides the economic case for investing in the governance and infrastructure fixes the amendment aims at.
2. NITI Aayog’s master-plan implementation gap: A NITI Aayog assessment has flagged a persistent gap between what city master plans formally provide for, including drainage, green cover, and building density norms, and what is actually implemented on the ground, identifying weak enforcement rather than a lack of planning provisions as the core problem.

Conclusion

Urban flooding and summer overheating in Indian cities share a common origin in master plans that have not kept pace with actual urban density and climate conditions, and the 2025 Section 41A amendment creating Urban Disaster Management Authorities is a governance response to that gap. Whether the new authorities close the NITI Aayog-flagged implementation gap will depend on the staffing and enforcement powers States actually give them, not on the amendment’s existence alone.

Back2Basics: Urban heat island effect

1. The pattern by which densely built urban areas record measurably higher temperatures than their surrounding rural or less-developed areas, caused primarily by concrete and asphalt surfaces absorbing and re-radiating heat.
2. Intensified by the loss of urban tree cover, water bodies, and open green space that would otherwise moderate local temperature.
3. Compounds public health risk during heatwaves, since urban residents, especially in dense, low-income settlements with limited cooling access, face higher effective temperatures than official city-wide readings suggest.
4. Addressed in India through urban greening and cool-roof initiatives under various city climate action plans, alongside the disaster-management governance changes covered above.

Matching Previous Year Question

“[2024, GS3, 15 marks] Flooding in urban areas is an emerging climate-induced disaster. Discuss the causes of this disaster. Mention the features of two such major floods in the last two decades in India. Describe the policies and frameworks in India that aim at tackling such floods.”