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# Fully considering soils in the urban planning and development processes: replicable examples from Nantes Metropolis (France)

Cécile Le Guern

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Cécile Le Guern. Fully considering soils in the urban planning and development processes: replicable examples from Nantes Metropolis (France). IFLA 2025 World Congress, IFLA, Sep 2025, NANTES, France. hal-05056927

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Submitted on 6 May 2025

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# Fully considering soils in the urban planning and development processes - replicable examples from Nantes Metropolis (France)

C. LE GUERN¹,²

¹BRGM, NANTES, France, ²IRSTV, NANTES, France

## Type selection

**Preferred Presentation Type:** Oral communication

## General data

**Topic:** Guiding cities through what is alive : Soil management

## Abstract text

**Text:** Soils are often considered from a risk perspective (pollution, geotechnics) in the urban environment. This is particularly the case in redevelopment projects. Being part of the ecosystem, soils represent also a vital resource. They are indeed a major source of biodiversity (in and above). They also sink carbon, store and infiltrate water, transform organic matter and nutriments. In this frame, in addition to supporting human activities, soils contribute to eg. regulate the climate and the water cycle, support the production of biomass. Planning and (re)development processes must consider soils as resource and as risk, whatever the scale of approach. Several R&D projects on soils used Nantes Metropolis territory as a case study. The objective is to present some results corresponding to knowledge, methods and tools that can serve landscape architects.

Excavated soils are a resource. They can be reused, from one site to another or through a valorisation platform. The TERRASS¹ numerical tool helps to put producers and receivers (users) in contacts and to fulfil the traceability obligations. In case of low to moderate contamination, which is frequent in the urban environment, the local geochemical background²,³,⁴,⁵ serves to establish threshold values to facilitate the reuse of excavated materials at district to territorial scale⁶. Soil refunctionalisation or construction⁷ can also be operated, using eg. excavated soils and organic waste. This can compensate for the scarcity of topsoil.

Soil multifunctionality helps taking the soil resource into account in planning and development. The MUSE method⁸ considers four estimated indicators of soil ecological functions (carbon storage, biodiversity storage, infiltration capacity, agronomic value) at territorial scale, and their combination. The maps can be used to preserve some good or patrimonial soils or anticipate soil restoration needs. Methodological adaptations at project (eg Ris-Orangis⁹) to territorial scale (eg. Rennes Metropolis¹⁰) aim to gain precision. Larger sets of indicators¹¹ and more detailed soil maps¹² allow adapting their use according to their quality, including multifunctionality as well as contamination.

Soil pollution risks are linked to different sources. Urban historical inventories map the former industrial and service activities potentially source of soil pollution²,³, and can guide on associated potential pollutants. Anthropogenic deposits may also be a source of pollutants, according to the nature of materials they contain¹³. Further research efforts are in progress within the GSEU¹⁴ and PERMEPOLIS¹⁵ projects. Agriculture, like market gardening, and green spaces maintenance may also have generated diffuse soil contamination with pesticides¹⁶. That is why, soil contamination risk needs to be checked before any project. In this frame, the high demand for urban gardening appears as a real challenge needing a careful check of soil quality(16).

Soils (including resource and risk) are fully considered in the DésiVille17 method to map their potential for desealing, additional development being in progress within the PERMEPOLIS15 project. Other inspiring examples exist at national to EU scale. The webtool in progress (SPADES18) aims to help the users (including landscape architects) to find the right soil concept/methods/tool to answer their needs in the planning, developments and/or design process.

## References

**References:** 1 TERRASS : https://ssp-infoterre.brgm.fr/fr/application/terrasse

2 Le Guern C., V. Baudouin, E. Bridier, C. Cottineau, M. Delayre, F. Desse-Engrand, M. Grellier, E. Milano, A. Mouny, S. Pollett, B. Sauvaget, A. Ménoury, P. Bâlon with the collaboration of P. Conil and L. Rouvreau (2016) Développement d'une méthodologie de gestion des terres excavées issues de l'aménagement de l'Ile de Nantes - Phase 1 : Caractérisation des sols et recensement des sources de pollution potentielles. / developing a methodology to manage excavated soils from the Ile de Nantes redevelopment - Phase 1 : characterisation of soils and inventory of potential sources of pollution. Rapport/Report BRGM/RP-66013-FR, 122 p., 27. Ill., 7 Annexes. https://infoterre.brgm.fr/rapports/RP-66013-FR.pdf

3 Le Guern C., V. Baudouin, B. Sauvaget, E. Pineau-Jamin, C. Gaubert, R. Braud, F. Desse-Engrand, S. Polett, A. Ménoury with the collaboration of G. Bodéré, E. Milano, P. Conil et P. Bâlon. (2017) Développement d'une méthodologie de gestion des terres excavées issues de l'aménagement de quartiers nantais - Phase 1 : Caractérisation des sols et recensement des sources de pollution potentielles/ Developing a methodology to manage excavated soils from Nantes districts redevelopment - Phase 1 : characterisation of soils and inventory of potential sources of pollution. Rapport final. BRGM/RP-67138-FR, 116 p., 48 ill., 30 tabl., 4 ann. https://infoterre.brgm.fr/rapports/RP-67138-FR.pdf

4 Le Guern C., Baudouin V., Sauvaget B. with the collaboration of Dubrac N. (2023) - Economie circulaire des terres excavées et transition écologique - accompagnement du projet d'aménagement Pirmil-les-Isles/ circular economy of excavated soils and ecological transition - accompanying the Pirmil-les-Isles redevelopment project. Rapport final V1/Final report V1. BRGM/RP-73276-FR, 104 p. https://infoterre.brgm.fr/rapports/RP-73276-FR.pdf

5 ADEME (2018) Méthodologie de détermination des valeurs de fonds dans les sols : Echelle territoriale. Groupe de travail sur les valeurs de fonds. / French methodology to determine pedogeochemical baseline: territorial scale. 112 p. Revised version to be published soon

6 Coussy S., Dubrac N., Hulot C., Billard A., Kaabouch S. (2020) Guide de valorisation hors site des terres excavées issues de sites et sols potentiellement pollués dans des projets d'aménagement. Ministère de la transition écologique et solidaire, 59 p.

7 Damas O. et Coulon A. (2016) Créer des sols fertiles : Du déchet à la végétalisation urbaine. Editions Le Moniteur, Antony, 336 p. (EAN : 9782281140965). / Create fertile soils: from waste to urban vegetalisation

8 Branchu P., Marseille, F., Béchet B., Bessière J.-P., Boithias L, Duvigneau C., Genesco P., Keller C., Lambert M.-L., Laroche B., Le Guern C., Lemot A., Métois R., Néel C., Sheriff R. (2021). MUSE. Intégrer la multifonctionnalité dans les documents d'urbanisme. Rapport final, 155 pages et Rapport d'annexes, 194 pages / Integrating soil multifonctionality in urban planning documents.

9 Ris-Orangis amène la santé des sols dans l'urbanisme réglementaire: https://www.lemoniteur.fr/article/ris-orangis-amene-la-sante-des-sols-dans-l-urbanisme-reglementaire.2343543

10 Le Guern C., Deslandes B., Boivin B., Lucassou F., Clozel B., J. Rillard, A. Péan, E. Bouriau, F. Tresse (2025) Prise en compte de la qualité des sols dans la trajectoire Zéro Artificialisation Nette (QuaSoZAN) - Développements méthodologiques appliqués à Rennes Métropole. Rapport final V0. BRGM/RP-74153-FR, 80 p. / Taking soil quality into account in the No Net Land Take and Zero degradation objectives - methodological developments applied to Rennes Metropolis
11 Séré G., C. Le Guern, A. Bispo, C. Layet, C. Ducommun, M. Clesse, C. Schwartz, L. Vidal-Beaudet, 2024. Selection of soil health indicators for modelling soil functions to promote smart urban planning, Science of The Total Environment, Volume 924, 2024, 171347, ISSN 0048-9697, https://doi.org/10.1016/j.scitotenv.2024.171347.

12 Ducommun C., Duvigneau C. et Vidal-Beaudet L., 2023. Cartographie des sols urbains : Méthode de caractérisation d'une couverture pédologique soumise à différentes formes de dénaturation et d'anthroposolisation Étude et Gestion des Sols; https://www.afes.fr/ressources/cartographie-des-sols-urbains-methode-de-characterisation-dune-couverture-pedologique-soumise-a-differentes-formes-de-denaturation-et-danthroposolisation/

13 Le Guern, C., Baudouin V., Sauvaget B., Delayre M., Conil P., 2018. A typology of anthropogenic deposits as a tool for modeling urban subsoil geochemistry: example of the Ile de Nantes (France). Journal of Soil and Sediments. https://link.springer.com/article/10.1007/s11368-016-1594-z

14 Asch K., H. Bauer, S. Bergman, A.-C. Flindt, P.Heckmann, C. Le Guern, H.-Georg Krenmayr, Zoltán Németh, Matevž Novak., Marco Pantaloni, Kris Piessens, Robert Schäfer, and Urszula Stepien (2025). One step beyond: The rocky path towards the new GSEU lithology vocabularies. Session: ESSI4.5 – Geologic Mapping in Challenging Environments: From Ocean Floors to Outer Space, EGU General Assembly 2025, 28/4-2/5, Vienna EGU25-11629

15 https://www.brgm.fr/fr/projet-cours/permopolis-vers-strategies-territoriales-efficaces-desimpermeabiliser-sols-urbains / Towards efficient territorial strategies to desal urban soils

16 Bouzouidja R, Béchet B, Hanzlikova J, Sněhota M, Le Guern C, Capiaux H, Jean-Soro L, Claverie R, Joimel S, Schwartz C, Guénon R, Szkordilisz F, Musy M, Körmöndi B, Cannavo P, Lebeau T (2020) Simplified performance assessment methodology for addressing soil quality of nature-based-solutions. *J Soils Sediments*. https://doi.org/10.1007/s11368-020-02731-y

17 Bodénan P., Doux H., Lebeau T., Capiaux H., Jean-Soro L, Le Guern C., Cannavo P., Vidal-Béaudet L., Béchet B. (2022) « Le jardinage urbain : le défi de la qualité des sols urbains pour les collectivités », *Projets de paysage*, 27 | 2022, http://journals.openedition.org/paysage/31684 ; DOI : https://doi.org/10.4000/paysage.31684

18 DésiVille : https://librairie.ademe.fr/urbanisme-territoires-et-sols/7889-desiville-ou-et-comment-desimpermeabiliser-les-sols-urbains-.html

19 SPADES https://www.spades4soils.eu/

**Keywords**

Keyword 1: soil

Keyword 2: resource

Keyword 3: risk

Keyword 4: methods

Keyword 5: tools

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