• Three major cities, Delhi, Ahmedabad and Mumbai, have been the victim of urban flooding almost each year.
• Delhi has seen four major flooding events between 2005 and 2023.
• Cities like Hyderabad (in 2000), Srinagar (in 2014), Chennai (in 2021) and Bengaluru (in 2022) have also seen some areas being submerged during heavy rainfall.
• A majority of urban resident’s face water-logging and traffic congestion.
• Baroda has lost 30% of its wetlands between 2005 and 2018 whereas Delhi had lost 300 waterbodies since 1997.

Urban flooding

• Urban flooding is a manmade disaster that is marked by the flooding of land or property in a built environment of a densely populated cities where rainfall exceeds drainage systems'' capacity.
• Urban flooding is caused not only by higher precipitation but also by unplanned urbanization, while rural floods are caused by heavy rain over a flat or low-lying area.

Factors leading to Urban flooding

Unplanned Urbanisation

• Rise in population leads to unplanned urbanization causing rise in construction activities especially in low-lying areas resulting in loss of water bodies.
• Cities are getting more concretized (via pavements, roads, and settlements), and hence rainwater percolation has reduced, leading to a rise in stormwater run-off.

Cities are situated beside a river

• Most Indian cities are situated beside a river, with extensive floodplains and wetlands.
• India has lost 40% of its wetlands in the past 30 years.
• With such a loss of natural “blue infrastructure”, flooding risks have increased.
• Blue infrastructure relates to urban water infrastructure, including ponds, lakes, streams rivers and storm water provision.
• Similar patterns exist for other cities.

Solution

Understand the problem better

• Studies must be conducted in all cities to understand the catchment area and flooding risk associated with urban water bodies (including rivers) and land use.
• This can then be tied up with short, medium and long-term measures to rejuvenate water bodies.
• Lake and river management plans should be defined and include the participation of the local citizenry in upkeep and a push to remove encroachments.
• Geographic information systems (GIS) may be used to tag local water bodies, to help keep track of encroachments and understand their seasonality.

Increase investments

• Investments are required in more early warning systems (including Doppler radar) to enable real-time updates on changing weather patterns locally.
• A Doppler radar is a specialized radar that uses the Doppler effect to produce velocity data about objects at a distance.
• Local rainfall data can be integrated with the Central Water Commission and regional flood control efforts.
• As rainfall patterns change, simulations will be required, particularly for flooding hotspots.
• Ideally, this can be linked with flood risk maps and insurance products.
• There should be investment in city-wide databases that enable the provision of immediate relief in the event of a flooding-related disaster.

Revamp and expand drainage and stormwater networks

• Most of India’s 5,000 plus cities and towns don’t have a well-functioning sewerage network.
• For example, Delhi’s drainage network can carry a maximum of 50mm in 24 hours, as significant parts require repair.
• Its stormwater drains are very old.
• Several areas have drains which have been incorrectly sloped against gravity.
• Other areas have no distinct drains for drainage and stormwater, often leading to overflowing.
• Most cities need to develop drainage master plans.
• Existing pipelines need to be surveyed (whether drain or stormwater), and water-logging locations shall be identified.
• Building this infrastructure should be given adequate attention.
• Stormwater networks should be kept separate from the drainage network.

Medium-to-long term urban planning has to improve

• In cities like Delhi, many civic agencies manage the city’s drains, leading to coordination challenges, information not shared or shared with delay, leading to a lack of transparency.
• Coordination between agencies/institutions must improve.
• For example, Delhi, with its Jal Board, seeks to revive 155 water bodies in a piecemeal manner.
• All this when water bodies are regulated by institutions ranging from Delhi Development Authority (DDA), to Delhi Jal Board, Public Works Department, and municipal corporations.

Awareness about wetland/water body conservation must be improved

• The Wetland Authority of Delhi has received requests to delist 232 (of 1,045) waterbodies from institutions like the Delhi Development Authority, this highlights limited awareness.
• The progress made by the Centre for the National Mission for Clean Ganga, Census on Pan-India water bodies, guidelines for conserving water bodies, and increasing Ramsar sites were significant.
• However, India requires a well-defined urban water policy.
• Regulatory bodies like the Central Wetland Regulatory Authority can be granted statutory powers

Replicate local examples- Mangalore & Kaikondrahalli Lake

• Government should identify and replicate local examples.
• Example: in Mangalore until the mid-2000s wastewater from urban consumption would flow through open drains and into the city’s water bodies, polluting the freshwater sources.
• The Mangalore City Corporation (MCC) has then established wastewater treatment plants with end-user linkages.
• Many industries were set up within the Mangalore Special Economic Zone Ltd (MSEZL) that faced a limited supply of water and, consequently, they ended up spending significantly on water sourcing.
• The MCC offered to supply treated effluent to MSEZL to meet its industrial need, with MSEZL-based private players sourcing about 70% of operations and maintenance costs of the pumps and the sewage treatment plant.
• Increasing demand for input water led to a ramp-up of two additional tertiary treatment plants, with the network expanding to cover 350 km of pipelines.
• Example: The Kaikondrahalli Lake in Bengaluru has suffered from severe sewage inflow, with silting and land formation due to eutrophication.
• Meanwhile, encroachment on the lake bed was a cause of concern, along with the dumping of debris and waste.
• BBMP adopted a community-driven approach to revive the lake in a phased manner as funds came by.
• Between 2009 and 2011, BBMP demarcated the lake’s boundaries to identify and stop encroachments.
• Encroachers were served eviction notices, and the lake was secured.
• Then, BBMP decided to tackle pollution, with sewage inflow diverted away via a tapping pipeline.
• Desilting of the lake was conducted to remove the vegetation growing in the lake and to increase the lake’s depth by 1m (also its storage capacity by 54%.
• Restoration was carried out by developing inlets and outlets for the lake and creating embankments and a pathway around the waterbody.
• All of this was done with local participation.
• The original Detailed Project Report (DPR) was rather engineering-focused, pushing for creating gardens and fencing off the lake from the local underprivileged communities.
• Citizen engagement ensured that the DPR was modified to improve the local ecology, instead of mere aesthetics.
• The plan was modified to ensure the watershed area of the lake was preserved while indigenous trees were planted.

As India advances, the cities of India must lead on climate change, rather than simply reacting to untoward events. Instead of pursuing smart cities, the authorities should invest in developing infrastructure like rainwater harvesting and better drainage system to deal with Urban floods. It’s time citizens of India get the basics right.