Toward an integrated method for the multifunctional assessment of nature-based solutions in urban environments

The implementation of nature-based solutions can be a way to adapt urban environments to the current and future consequences of climate change such as flooding, heat waves and biodiversity loss. However, it is limited by its lack of integration into multi-criteria assessment tools and by an insufficient understanding of how the efficiency of NbS evolves across different spatial scales within a territory.

Therefore, an integrated method for assessing the multifunctionality of NbS across spatial scales is planned to be developed.

First, a multi-scale, distributed modelling is carried out to simulate thermo-hydric processes and fluxes (e.g. infiltration, evapotranspiration, runoff and temperature) associated with some NbS performances and climate adaptation measures at different urban scales.

Secondly, a systemic approach will be taken to study additional ecosystem services (e.g. habitat creation to enhance local biodiversity) and the environmental impacts of NbS (e.g. carbon emission and water consumption). These models will be implemented on different urban French pilot sites.

Finally, scale-invariant tools with a multifractal framework will be used to study the inputs and outputs maps and times series of the models. This will overcome the limitations of standard scores, which are only valid at a given resolution, and enable performance indicators to be computed independently of spatial scale while considering associated uncertainties.

Preliminary results will be presented here. They concern the multi-scale and distributed modelling under development. The Multi-hydro platform, developed by the HM&Co lab at ENPC, is coupled with SOLENE-Microclimat, in order to represent the interaction between both water and energy balances. They have been applied on one of the pilot sites. In parallel, modules to simulate the behavior of different nature-based solutions are also being developed. A trait-based model will also be integrated later to take the kinetics of plant development into account. These modules will be validated through experimental measurements.

This work is being carried out as a part of the French ANR project PENATE (Planning and Evaluating Nature-Based Solutions with local authorities), which aims to assess the performance and effectiveness of NbS as a tool for adapting urban environments to climate change.