Mitigating risks, impact of flooding in the cities

There are two primary reasons for the flooding. Floods are an outcome of heavy rainfall, and these extreme events are increasing due to the climate crisis. In the last decade, compared to the previous 30 years, an analysis by the Council on Energy, Environment and Water (CEEW) has shown that more than 64% of Indian sub-districts or tehsils have witnessed an increase in heavy rainfall days. Not only that, this heavy rainfall often comes in short bursts of intense rain. We found that cities such as Pune, Ahmedabad, Jaipur, and Hyderabad are especially affected. But human activities also accentuate the impact of flooding. Poor regulations related to land-use-and-change policies often disrupt drainages that are natural conduits for water flow. This leads to higher water runoff from dense built-up areas during heavy rainfall or storms. Poor implementation of solid waste management policies end up choking the waterways in our cities and towns even further. Finally, inadequate design of stormwater drains leads to slow outflow, leading to waterlogging.

It’s high time we rethink how to deal with urban floods and move from reaction to readiness. The solution lies in improving our preparation — pre-monsoon, during monsoon, and post-monsoon. This is where an action plan to manage flood risks can be a useful tool. Such a plan should ideally cover two important checks.

First, urban local bodies must reassess the intensity-duration-frequency of storm events by looking into the latest rainfall patterns and revising the peak flood flow and volume data. In fact, such assessments are usually not undertaken regularly at the city level, often leading to stormwater drains being designed based on old data and making their capacity insufficient to handle heavy rain. For instance, CEEW’s assessment shows that Thane in Maharashtra lacks a stormwater drainage system that can manage peak flow generated from one hour of heavy rain, which has been around 64 mm/hr for the city in the last decade. The Thane Municipal Corporation has taken cognisance of these revised estimates and is considering designing new stormwater drains based on them.

Second, authorities should undertake flood risk assessments to identify “hot spots” in a city. This involves identifying risks posed by hazards related to extreme rainfall, exposure of “assets” such as hospitals and schools to extreme rainfall events, and vulnerability, including the adaptability of communities to cope with the adverse impacts of extreme rainfall events.

Finally, it’s important to manage flood risk through specific interventions over the short, medium, and long term — and not just when a city floods. The action that should be taken immediately is the strengthening of the weather monitoring system, as per the World Meteorological Organisation norms. Doppler weather radars, which have been recently installed in various cities, can be crucial in precise rainfall forecasts. Another short-term measure can be designing campaigns to nudge community behaviour to handle solid and other waste better so that it does not clog drains. For instance, the city of Indore was instrumental in successfully sensitising citizens to segregate their waste at source and not to dump garbage in open areas. Similar efforts by the cities of Tirupati and Alleppey offer good examples to learn from.

Finally, urban local bodies must separate stormwater and sewerage systems, which are often one and the same in Indian cities.

In the medium term, establishing an Urban Flood Management Cell to coordinate with different agencies in charge of developing and managing public urban infrastructure is crucial. Moreover, replacing ageing stormwater drainage infrastructure is essential — as Cuttack in Odisha has done. However, the drains must be designed according to the latest rainfall pattern assessments.

In the long term, rejuvenating local wetlands and water bodies, which act as sponges, is key. The 15th Finance Commission allocated ₹2,500 crore for reducing flood risk across seven major cities in India such as Mumbai, Chennai, and Kolkata. We must explore the potential of nature-based solutions, such as integrating wetlands with the existing grey infrastructure in the city. To scale up such solutions, use a unified framework for mapping and estimating benefits to bring in targeted investments.

Flooding and heavy rainfall are becoming the new normal in India. Our cities must urgently become flood-proof, and not just respond in monsoon months. For cities, risk-informed water planning all year round is the way forward. It saves lives and livelihoods.

Nitin Bassi and Vishwas Chitale are senior programme leads with the Council on Energy, Environment and Water (CEEW). The views expressed are personal