Integrated urban flood management at the Kosasthalaiyar Basin

Tamil Nadu’s capital is prone to flooding and relied on energy-intensive processes to combat its flood risks. We reinforced storm drains, used nature-based solutions, and conducted training programmes to create a more inclusive, sustainable approach to flood resilience.

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Aerial view of urban flood management infrastructure in Chennai’s Kosasthalaiyar Basin, integrating waterways, green spaces and sustainable drainage systems.

Project facts

Client: Greater Chennai Corporation (GCC) - Storm Water Drain Department
Location: Kosasthalaiyar Basin, Chennai, Tamil Nadu, India.
Period: 2021-2025
Challenge: Mitigating urban flood risks, improving sustainability, and addressing social inequality.
Solution: Reinforced storm drains, nature-based solutions, and sustainable gravity-driven drainage.

Aerial view of the Kosasthalaiyar Basin area in Chennai before intervention, showing flood‑prone urban land and water bodies historically affected by high flood risk, groundwater depletion and biodiversity loss.

The challenge

The Kosasthalaiyar Basin in Northern Tamil Nadu is a vital water source that sustains the capital city of Chennai.

Historically, it has struggled with high flood vulnerability, with millions of residents facing annual property loss and health risks. The region relied heavily on expensive, reactive measures like emergency diesel pumping to combat these risks.

Beyond flooding, the area also faced declining groundwater levels, loss of biodiversity, and the marginalisation of vulnerable groups – including transgender individuals and sanitary workers – who were often excluded from formal disaster response and resilience planning.

The solution

Haskoning worked alongside Mukesh & Associates and Struct House Pvt. Ltd to develop a climate-resilient, integrated management plan that moved away from "grey-only" infrastructure toward a nature-integrated ecosystem.

The plan consisted of several elements:

The construction of 762 km of high-quality, reinforced storm water drain infrastructure, strategically interlinking 78 local water bodies.
Nature-based solutions that integrate "sponge parks", rain gardens, and eco-block recharge systems to facilitate natural water absorption.
The transformation of the 135-acre Kadapakkam Lake, which included the creation of a five-acre "Bird Island" that now serves as a habitat for 46 avian species.
A transition from energy-intensive pumping systems to a sustainable, gravity-driven drainage network.

Nearly 1.9 million residents in the project area are directly benefitting from our work. And our strong EST purpose matrix score reflects our commitment to safety, inclusivity, and sustainability.

Rajkumar Nelson AnbiahTeam Leader for the Integrated Strom water drain Kosasthalaiyar Chennai Project at Haskoning

The result

Our combined programme of work delivered flood mitigation, efficiency, environmental, and social benefits, including:

85% of annual flood-related losses mitigated and nearly 2 million inhabitants protected
89% average reduction in emergency pumping requirements
Annual operational savings of ₹40 million ($440,000)
A reduction of nearly 500 MT in carbon emissions
25–30% improved groundwater recharge
Significantly enhanced local biodiversity

The project also established flood wardens. These groups of volunteers deliver the first disability-inclusive and transgender-led disaster response mechanisms in the region.

Capacity‑building workshop supporting inclusive flood resilience and urban flood management in the Kosasthalaiyar Basin, Chennai.

Plus, we reconstructed essential access structures like steps and ramps to support elderly and disabled residents, and restored damaged compound walls for multiple residential properties and a local government school.

During construction, we also provided transitional allowances and economic assistance to people and business owners affected by disruption.

And we conducted several capacity building and training programmes, focusing on leadership, basin management, worksite safety, relief and rehabilitation, worker welfare, plastic pollution eradication, and the long-term upkeep of the storm water drain network.

In recognition of its exceptional results and inclusive approach, the project received Haskoning’s internal Enhancing Society Together award for 2025. The award celebrates employees who go beyond standard delivery to create lasting improvements in our projects and organisation, advancing positive impact for society.

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