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The Annual Deluge: Understanding Mumbai's Chronic Flooding Problem

Mumbai's rapid urbanisation and high population density pose a significant challenge to managing rainfall.

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Mumbai, the financial capital of the world’s fifth-largest economy, is flooded again. Last evening, I was invited to a TV show to discuss this issue with politicians and civil society activists. I told them that this is the fifth year in a row that we are discussing the Mumbai floods, and the discussions haven’t moved any further than the usual blame game.

Each year, during the monsoon season, Mumbai becomes synonymous with urban flooding. Is the recurrent inundation a natural calamity or an intricate problem rooted in several interlinked factors? Understanding these factors is crucial in seeking solutions to mitigate the adverse impacts.

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Heavy Monsoons: A Torrent of Trouble

Mumbai's monsoon season, which typically spans from June to September, brings substantial rainfall to the tune of an average of 2300 mm. The city often experiences extreme bouts of heavy rain in short periods. For instance, on the 7th and 8th of July, 2024, a record 170 mm of rain fell within three hours. In common parlance, it would be equated to around 6 inches of rainfall across the city of Mumbai. Such intense downpours can overwhelm the city's drainage capacity, leading to widespread flooding.

Mumbai's rapid urbanisation and high population density pose a significant challenge to managing rainfall.

Passengers wait for trains at a waterlogged railway station in Mumbai, during rains.

(Photo: PTI)

The Indian Meteorological Department often forecasts these heavy rains, but the city's infrastructure struggles to keep up with the sheer volume, leading to waterlogging and disruptions in daily life. Heavy monsoons are a natural part of Mumbai's climate, but their interaction with human-made vulnerabilities turns them into disasters.

Numerous reports by the Intergovernmental Panel on Climate Change (IPCC) have already sounded the alarm about the increasing frequency and intensity of heavy rainfall due to climate change. Many climate models support these findings, projecting that cities like Mumbai will face more severe monsoon seasons in the coming years. These projections are becoming a reality, exemplified by instances like the recent event.

The problem is that these events will be more pronounced in future. The combination of Mumbai’s intrinsic heavy monsoon rains and these human-made climate vulnerabilities casts a dire outlook for future flood management.

Poor Drainage Systems: A Failing Network

One of the most critical factors contributing to Mumbai's flooding is its outdated and inadequate drainage system. It was designed over a century ago during the British colonial period, with patchwork done year after year to cope with the situation. The current drainage network was intended for a much smaller population and less dense urban environment. As a result, the system is ill-equipped to handle the modern city's demands.

Clogging and poor maintenance further exacerbate the problem. Drains filled with plastic waste, debris, and silt block the water flow, causing it to back up and flood the streets. The municipal authorities have intensified cleaning and desilting operations ahead of the monsoon season, but these efforts often fall short amid the city's relentless growth and waste management challenges.

One of the key reasons Mumbai struggles to fix its drainage problems is the sheer complexity and scale of the challenge. The drainage system does not just need maintenance—it requires a complete overhaul. Upgrading such an extensive and deeply embedded infrastructure in an already densely populated city is both logistically and financially daunting.

Funding is a significant roadblock. Comprehensive upgrades involve large capital investments that compete with other pressing urban needs. Moreover, the bureaucratic red tape and overlapping responsibilities between municipal and state agencies often delay decision-making and execution.

Additionally, rapid urbanisation has outpaced infrastructure development. The constant influx of people and unplanned construction put continuous pressure on the drainage network. Encroachments and illegal constructions over natural water bodies further complicate matters.

Waste management poses another persistent issue. Despite intensified cleaning campaigns, the sheer volume of plastic waste and debris overwhelms the municipal systems, leading to clogged drains. Public awareness and participation in responsible waste disposal remain low, exacerbating the problem.

Considering these multifaceted challenges, effective solutions will require coordinated efforts, substantial investments, and systemic urban planning and governance changes to create a robust and resilient drainage system for Mumbai.

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High Population Density and Urbanisation: A Concrete Jungle

Mumbai's rapid urbanisation and high population density pose a significant challenge to managing rainfall. The city's landscape is dominated by concrete, reducing the natural absorption of rainwater. Paved surfaces, buildings, and infrastructure replace green spaces and wetlands, leaving rainwater with limited places to go.

This extensive concretisation has led to an increase in surface runoff, burdening the drainage systems even more. The situation is compounded by informal settlements and slums, which often lack proper drainage facilities, making them particularly vulnerable to floods.

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Encroachments and Construction: Blocking the Flow

Unplanned construction and encroachments on natural water bodies have severely impacted Mumbai's ability to handle heavy rains. Lakes, ponds, rivers, and other natural water channels that historically absorbed and diverted rainwater are now obstructed or built over.

These water bodies, which once were crucial in flood management, are often turned into residential or commercial areas. This unplanned development chokes the natural pathways through which rainwater traditionally flows away, causing it to stagnate and flood urban areas instead.

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Sea Level and Tidal Influence: The Coastal Conundrum

Mumbai's unique geographical placement along the Arabian Sea further complicates its flooding issues. Significant parts of the city are at or below sea level, making it vulnerable to high tides, particularly during the monsoon season. During high tides, the sea can prevent rainwater from draining out, causing it to back up and flood the land.

Additionally, with climate change leading to rising sea levels, this problem is expected to worsen. Storm surges and tidal actions exacerbate flooding, particularly in low-lying coastal neighbourhoods.
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Climate Change: An Emerging Threat 

Climate change plays an increasingly significant role in Mumbai's flooding. As global weather patterns change, the city is experiencing more intense and frequent rainfall events. These erratic weather patterns can strain an already burdened infrastructure.

Projections indicate that climate change could lead to heavier monsoon rains and higher sea levels, potentially leading to more severe and frequent flooding. This makes it imperative for Mumbai to adopt climate-resilient urban planning and infrastructure development.

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Addressing the Challenge: A Multi-Faceted Approach

The recurring floods in Mumbai necessitate a comprehensive and sustained effort to mitigate their impact.

First and foremost, upgrading and expanding the drainage network is critical. This includes increasing the capacity of drains, ensuring regular maintenance, and implementing advanced drainage technologies such as pumping stations and stormwater retention systems. Sustainable urban planning is equally important; a balance between development and environmental conservation is needed.

Second, protecting natural water bodies, creating more green spaces, and enforcing strict regulations on construction in vulnerable areas are essential measures. Community engagement is also crucial; public awareness and participation in waste management and conservation efforts can significantly reduce drainage system burdens. Community-based initiatives for cleaning drains and promoting rainwater harvesting can be effective.

Third, developing and implementing climate adaptation strategies is crucial. This includes building climate-resilient infrastructure, investing in early warning systems, and enhancing disaster preparedness.

Lastly, effective policy and governance are needed to manage urbanisation and protect natural water bodies. Coordinated efforts between municipal authorities, the state government, and the community can lead to more effective flood management.

While Mumbai's monsoon-induced flooding is a complex challenge, a multifaceted approach that combines infrastructure upgrades, sustainable planning, and community engagement holds promise for a more flood-resilient future. Addressing the root causes of flooding and adopting proactive measures to cope with climate change can help mitigate the annual deluge and safeguard the city's vibrant life.

(Anjal Prakash is a Clinical Associate Professor (Research) at Bharti Institute of Public Policy, Indian School of Business (ISB). He teaches sustainability at ISB and contributes to IPCC reports. This is an opinion piece and the views expressed are the author’s own. The Quint neither endorses nor is responsible for them.)

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