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.

Causes

Climate is loading the dice: warmer air holds more moisture, so extreme daily rainfall is more likely. Urbanisation seals soil with asphalt. Wetlands, tanks and floodplains — the city’s old sponges — are plotted and built. Storm-water drains are undersized, blocked with solid waste, and often combined with sewage. Encroachment on riverbanks (Mithi, Cooum, Adyar, many nallahs) removes the channel. Tidal lock in coastal cities stops drainage at high tide. Upstream dams and sudden releases can add a pulse. Poor mapping and housing on low ground put the poor in the first storey of the flood. The disaster is therefore climate plus planning plus garbage, not rain alone.

• Peg: Extreme rain is the climate limb; the sealed floodplain is the governance limb.
• Peg: Solid waste in a drain is a flood policy failure, not a civic footnote.

Two major floods

Mumbai, 26 July 2005. A record single-day downpour over the city, with the Mithi overflowing, airports and rails stopping, and large loss of life in low-lying and slum belts. Features: an extreme rain event, a river-turned-drain, high tide, and a megacity whose suburbs had eaten the catchment. The Fact-Finding Committee (Chitale) and later work made the Mithi and storm drains a public file.

Chennai, November–December 2015. Weeks of excess northeast-monsoon rain, overflow of Chembarambakkam and other tanks, the Adyar and Cooum in spate, a city-wide halt, and a death and livelihood toll that made it a national disaster. Features: a reservoir-and-tank system that could not be operated only as flood control, wetland loss (including the IT corridor’s relationship with the marsh), and rainfall that sat far above what the colonial-era drain assumed.

(Other large events exist — Uttarakhand 2013 is more mountain than city; Kerala 2018 was statewide; Hyderabad 2020 and Bengaluru 2022 were serious urban floods. The question asks for two; Mumbai 2005 and Chennai 2015 are the clearest megacity pair.)

• Peg: Mumbai 2005: one brutal day, Mithi, tide, transport collapse.
• Peg: Chennai 2015: a monsoon month, tanks and rivers, wetland memory.

Policies and frameworks

The Disaster Management Act, 2005, and NDMA guidelines on urban flooding (2010) ask cities for drainage master plans, wetland protection, and early warning. State disaster plans and city Heat-and-Flood SOPs sit under SDMAs. AMRUT and Smart Cities fund storm-water and some lake revival. National Water Mission and wetland rules (including the Wetlands Rules, 2017) try to keep sponges legal. Model Building Bye-Laws and some State rules require rainwater harvesting and, in a few cities, zero-dumping into nallahs. NGT orders on lakes and construction-and-demolition waste are a judicial track. National Cyclone Risk Mitigation and coastal zone rules matter for tidal cities. The gap is municipal capacity and encroachment politics: a guideline does not move a mall off a drain. Climate policy (National Action Plan, State Action Plans) now names urban flooding as an adaptation item, which is the right heading if the budget follows the drain, not only the flyover.

• Peg: NDMA urban flood guidelines plus the DM Act are the national framework; AMRUT/Smart Cities are the money pipes.
• Peg: Wetland Rules and lake litigation are the ecological half of the same policy.