Issues and needs
In cities, the problems caused by soil sealing (flooding due to rainwater run-off, the effects of urban heat islands on the well-being of residents) are being exacerbated by climate change. Consequently, unsealing surfaces has become a necessity. However, unsealing also comes with potential disadvantages which must be taken into account, for example the risk of freeing pollutants contained in the sealed soil or accentuating the risk of flooding due to rising groundwater levels.
Surface unsealing is a key stage in the renaturation process and is also part of the response to achieving the European objective of "zero net artificialisation" (ZNA) by 2050, as set out in the Climate and Resilience Act adopted in August 2021. The market for unsealing is therefore growing quickly.
However, local authorities currently lack the requisite tools and methodologies, notably to establish unsealing strategies at different levels in their regions.
Expected results
The project's primary goal is to develop a method that can be used in collaboration with the various stakeholders to co-construct optimised unsealing strategies and the associated tools.
- Drawing on input from a GIS, the resulting multi-criteria analysis tool will improve the reliability of the map of areas that could potentially be unsealed (based on the analysis of benefits and risks, the uses, stakeholders' points of view and any uncertainties) and thus help in the co-construction of unsealing scenarios.
- A serious game designed for the various stakeholders will facilitate the co-construction process by helping them to understand the complexity of urban areas and the issues involved in unsealing.
- The project will also produce thematic maps of the pilot study area (Nantes Metropolitan Area) to improve knowledge of the urban system, while incorporating a presentation of any related uncertainties. Artificial intelligence and geostatistics will be used to address the uncertainties, which will be categorised in a concerted manner in order to facilitate their integration in the GIS and ensure they are taken into account in the decision-making process.
Programme du projet PerméPolis.
© BRGM
BRGM’s role
BRGM is responsible for the overall management of the project. It will also lead Task 1, which focuses on the characterisation of sealed surfaces. This task includes physical characterisation based on airborne hyperspectral data, as well as the analysis of land-related, regulatory and legal issues. BRGM is also involved in Task 2, which deals with the characterisation of the benefits and risks associated with unsealing.
In particular, it will coordinate work to improve the mapping of potential sources of pollution due to unsealing, by testing how urban geophysical data and AI-driven geostatistics can contribute to mapping intrinsically contaminated backfilling. In addition to this, BRGM will contribute to characterising the vulnerability of groundwater to soil contamination and to integrating a qualitative component into the hydrological assessment in order to evaluate the effect of unsealing scenarios on rainwater flows (infiltration and run-off), while also characterising the permeability of backfilling.
For the purposes of Task 3, which involves establishing methods for the co-construction of unsealing scenarios, BRGM will contribute to defining any uncertainties and improving the method for mapping the unsealing potential, as well as to the replication of the study. Naturally, BRGM will be involved in promoting and disseminating the project results.
Partenaires du projet PerméPolis.
© PerméPolis
Partners
Based on an interdisciplinary approach, the projects brings together public research institutes (G. Eiffel University, Nantes University, MinesParis-PSL, UTC, ESGT, ONERA, BRGM, CEREMA), a private partner (OTEIS) and a local authority (Nantes Métropole). The project is co-funded by the ANR.
