Antananarivo, the capital city of Madagascar, is normally exposed to intense floods during the rainy season. But this threat is now being increased by climate change, with rain more concentrated and more intense during the year. Most cities adapt to this risk by implementing infrastructures made of concrete, but they tend to simplify or even erase ecosystems. So, while they may control some of the flood risk, it will be at the expense of other dimensions like food production or other economic activities related to ecosystems. In Antananarivo, there is instead an opportunity to use peri-urban agriculture as flood control infrastructure. Over the years, farmers have developed multi-functional spaces that are able to cultivate food and provide other materials, while living with the change in water levels between seasons. For the future of the city, it is a sound strategy to recognize these practices and to enforce this model of limiting flood risk while conserving the livelihoods of people. It is also important that decision makers are aware of this option when making decisions about the future. It is for this reason that simply understanding multifunctionality is not sufficient; we must also engage with decision makers about different visions for the future.

Our aim is to improve the sustainability of the urban environment and its thermal comfort using rule-based scenario planning at various scales of the built environment whether it be district scale, neighbourhood scale, or individual buildings to optimise future developments.

Specifically, we explore different aspects, such as improving wind flow, preventing flooding, facilitating accessibility and walkability, and whether mixed-use developments contribute to reducing greenhouse gas emissions and adapting to projected climate change.

We focus on both climate mitigation and climate adaptation. For climate mitigation, special attention is given on improving outdoor thermal comfort through greening, shading, and improving wind flow. One of the focuses is on improving wind flow in the city to increase thermal comfort, by exploring variations in building heights, building footprints and setbacks, among others. 

In terms of climate adaptation, we focused in sea-level rise by allowing low-lying developments to be inundated without majorly affecting residents and by facilitating mangrove growth to provide a nature-based solution to improve resilience against strong waves and rising tides.

Pluvial flooding has also been taken into consideration:  we developed urban planning scenarios that impact stormwater run-off by either reducing it or keeping it unobstructed by buildings. These ideas have been applied to public housing, in order to collect and store rainwater to alleviate flooding issues, adopt nature-based solutions for filtering and cleaning water, and use collected water for domestic uses.

By combining these different scenarios, we can holistically aim to achieve a net-zero carbon city that not only adapts to and mitigates climate change, but also improves human comfort and well-being, while remaining economically prosperous.

Blue-Green infrastructures offer a feasible and valuable solution for urban areas by connecting urban hydrological functions with vegetation systems towards providing benefits that are greater than the sum of its individual components.

Future development of cities does not need to be on the opposite side of ecosystems sustainability. Integrated greenery components in building structures mitigate the footprint competition on the ground, rehabilitate urban green spaces and their network connectivity crossing urban areas for ecosystem services in three dimensions.

The concept of the ‘Garden City’ has been a key part of the urban development of Zurich since the 1940s. Green corridors and water bodies constantly interact with the urban fabric creating a network of elements which enhance the resilient capacity of the city. Air quality and temperature data show that blue and green infrastructures introduce cool air flows into the city, mitigate pollution and urban heat island effect and increase the liveability of the urban areas.