How can new green-grey hybrid technologies help flood-affected communities?

In Kochi, India, a network of canals has been used for transportation, fishing, and flood control for generations. But over time these canals have severely degraded, polluting waters and increasing flood risks. This has a detrimental impact on day-to-day life for those living along the canal. In a survey of more than 300 households, 44% experienced flooding during monsoons, reporting incidents when up to 3 feet of polluted water entered their homes. These events are set to increase, as climate change increases the frequency of extreme monsoons and raises water levels.

To address these challenges, bechtel.org (the social impact arm of engineering company Bechtel) collaborated with ICLEI-Local Governments for Sustainability, South Asia and Swiss Re to design a pilot restoration project using innovative hybrid infrastructure along 2km+ of the Pandarachirathodu Canal.

The collaboration, catalysed by a grant from the Swiss Re Foundation, proposed a green-grey hybrid solution named Integrated Wetland Technology (IWT).  This is an innovative natural sewage treatment, integrating native plant species into a gravity-fed water treatment system, allowing the IWT to act as a natural filter, cleansing polluted water. Rather than simply replacing a sewage treatment plant with IWT, the application of this system is also unique: pollutants that cause the canal to clog are also filtered, which will lead to flood reduction in the area. Together, these functions allow the canal to regenerate, providing the protection from flooding and polluted water that the community needs, as well as promoting sustainable livelihoods such as shrimp farming and ecotourism.

How can this technology benefit the community?

“This project will impact around 12,000-13,000 people by cleaning their canal and mitigating flooding during monsoon season…It’s projects like the Kochi Restoration Project which can help the world, the cities, and the communities who live here by giving them a sustainable solution to help protect their livelihood, their property, and their lives.”

—Tara Pillai, bechtel.org

What returns can this project have for stakeholders?

We used our Sustainable Asset Valuation (SAVi) methodology to evaluate the holistic impacts of this project for society, the economy and the environment. In our report, we focus on three potential intervention scenarios:

1. Implementing the Integrated Wetland Technology (IWT) to treat wastewater and prevent flooding.
2. Implementing IWT, combined with nature-based interventions, including floating wetlands and mangroves, as well as the removal of culverts to further restore the canal.
3. All of the above, plus the integration of a biodiversity park to support ecotourism and create jobs for the community.

Across the three scenarios, we quantified the construction, operations, and maintenance costs, avoided flood damages, health impacts, avoided water pollution from nitrogen and phosphorus, increased fishery production, carbon storage, and new jobs created from the biodiversity park and ecotourism.

We also considered the qualitative impacts of rice farming in the wetland area, Rice farming in Kochi has faced many challenges due to water pollution, high salinity of the water, and widespread floods, resulting in a drastic decline in cultivation in the region. By reducing pollution, improving water quality, and preventing harmful floods, the planned Kochi canal restoration activities could potentially benefit sustainable rice farming.

What did our assessment find?

Our assessment found all three scenarios to be investment-worthy, with the highest net benefit produced by Scenarios 2 and 3 (INR 325-331 million): the combination of Integrated Wetland Technology with a form of NBI. However, the highest benefit to cost ration (BCR) was Scenario 1, the baseline intervention of hybrid Integrated Wetland Technology. Here, for every INR 1 spent, INR 9.78 of benefits were generated for society, the economy and the environment.

This project embraces the potential of hybrid green-grey infrastructure to make a real difference to the everyday lives of residents along the canals in Kochi. The baseline intervention using Integrated Wetland Technology demonstrates the innovative potential of integrating green infrastructure solutions with traditional grey methods to realize greater benefits. The addition of further nature-based interventions in the Scenario 2 demonstrates the potential for even further gains for fishery production and carbon storage. Scenario 3 then offers a significant boost to the local economy through the construction of a biodiversity park and introduction of ecotourism, providing vital protection and habitats for wildlife suffering from the current pollution and flooding crises.

So, what’s next?

The goal is to demonstrate this as a viable, scalable, and repeatable solution for all of Kochi’s canal restoration projects. This assessment provides evidence that such an approach is investment-worthy, with demonstrable returns for society, the economy and the environment. Upscaling this approach to support more canal restoration could transform the situation in Kochi, helping the community adapt to climate change, improve public health and protect biodiversity.

We hope that the results of this assessment can be used to engage public and private sector actors in future project design and implementation, help to attract the necessary funding for these projects and to raise awareness of the innovative use of grey-green technologies that can be transferred to similar challenges across the world.

 

Read the report