Over 650,000 people live in high-risk areas in Antananarivo, which is prone to water pollution and urban floods. The high exposure to flooding presents a significant threat to people and assets in the flood plain, especially for the poor who don’t have the resources to address existing challenges, which include rapid urbanisation, extreme poverty, and rising crime.

Funded by the World Bank, the Integrated Urban Development and Resilience Project (PRODUIR) uses a combination of drainage and flood infrastructure upgrades, improvements in urban living conditions, and enhanced urban governance and disaster preparedness. 

Royal HaskoningDHV, along with lead research institute Deltares and partners BoschSlabbers, and Evolutis, performed a comprehensive assessment and pre-feasibility study on urban resilience adaptation strategies for the area. These strategies integrated nature-based solutions (NbS) and disaster evacuation planning to increase flood resilience and enhance living conditions in low-income neighbourhoods.

Working with nature

A system analysis identified existing challenges and provided insight into the water system and its connection to pluvial and fluvial flooding. Potential intervention sites and measures were identified, both structural and non-structural, to develop a flood resilience strategy integrating disaster evacuation routes and refuges with NbS measures, such as urban forests, retention ponds, and bioswales.

The analysis identified ten potential evacuation sites based on their size, scalability, and potential to tackle multiple challenges. Three specific sites and respective measures were being assessed in a pre-feasibility study. Each refuge site combines at least three NbS measures and incorporates suitable disaster evacuation routes. Technical design considerations for implementation, as well as maintenance, communication, and monitoring plans, were defined during this phase. 

Securing community buy-in

Nature-based solutions present an opportunity to address urban challenges in a resilient and inclusive way. They are versatile, scalable, use limited resources, and offer protection to vulnerable populations. During a disaster, they have the potential to provide safe and quick evacuation routes and a secure haven for displaced people.

The behavioural change that happens when the community experiences and understands the direct impact of NbS can have a positive economic impact. However, this requires adequate and timely communication of the benefits and impact of the measures.

The proposed NbS have low implementation costs and give co-benefits, such as safe escape during flooding. They can also be implemented and managed by the community. Stakeholder engagement helped to validate the findings of the pre-feasibility study, raise awareness, and obtain feedback on the strategy. 

When it comes to nature-based solutions and disaster risk management, the simplest measures are often the most effective. Working with nature and integrating targeted interventions in urban planning and disaster management can save lives and protect infrastructure and people during flooding.

The results of this project are described and visualised in the project i-Report.