Etude des trajectoires socio-écologiques et historiques de la plaine du Vistre (du XVIIIe siècle à aujourd'hui) pour penser le passé et le futur d'un fleuve côtier méditerranéen, Gard.

Study of the long term socio-ecological trajectories of the Vistre plain (from the 18th to nowadays) to think the past and future of a Mediterranean coastal river, South of France.

• Auteur / Autrice : Ghita Serrhini naji
• Direction : Marc Vinches, Raphaël Mathevet
• Type : Projet de thèse
• Discipline(s) : STE-Environnement, Territoires et Sociétés
• Date : Inscription en doctorat le 01/10/2021
• Etablissement(s) : IMT Mines Alès
• Ecole(s) doctorale(s) : Biodiversité, Agriculture, Alimentation, Environnement, Terre, Eau
• Partenaire(s) de recherche : Laboratoire : HSM - Hydrosciences Montpellier
• Partenaire(s) de recherche : Equipe de recherche : Eau, Ressources, Territoires

Mots clés

Mots clés libres

Communs

Interactions socioécologiques

Histoire environnementale

Gestion et gouvernance de l'eau

Attachements

Restauration de rivière

Communs

Socio-ecological interactions

Environmental history

Water management and governance

Attachements

River restoration

Résumé

Les changements globaux modifient les trajectoires d'évolution, à l'échelle locale des territoires, et questionnent leur capacité de résilience. Dans un contexte de fortes incertitudes liées à la complexité des signaux à prendre en compte (évolution des températures, des précipitations, des populations, des milieux, etc.), les politiques d'aménagement du territoire doivent pourtant faire des choix structurants entre différents scénarios d'adaptation et de transition. Ce projet s'inscrit dans le cadre des Long-Term Socio-Ecological Research ainsi que des recherches sur le Baseline Shifting, en posant l'hypothèse suivante : la compréhension des processus et des facteurs qui sous-tendent les dynamiques socioécologiques, et leurs évolutions dans le temps long, participe à identifier les jeux de pouvoir et les voies d'adaptation pour les pratiques et les actions collectives. Elle fournit ainsi un socle de savoirs essentiels à la prise de décision politique, en permettant de questionner la compréhension du référentiel dans lequel s'inscrit la perception des changements et des perturbations. La thèse proposée s'inscrit ainsi dans une démarche de recherche participative et de recherche-action. Elle doit contribuer à une re-découverte et une réappropriation par les acteurs locaux des raisons qui ont fondé, au fil du temps, les choix d'aménagement des générations antérieures, pour consolider et mieux légitimer le choix des scénarios d'adaptation ou de transformation à venir.

1. Context The Vistre is a coastal river that rises northeast of Nîmes (France). It crosses a watershed that witnesses a long history of interactions between human activities and waterways. The development of the waterways of the Vistre basin, already present in the 12th century, has continued until today to respond to multiple issues: drainage of the marshy plain through the creation of ditch networks, navigation with the creation of the Vistre canal, creation of diversion canals for mills and irrigated crops, etc. In the Age of Enlightenment, then during the French Revolution and again in the 19th century, the clearing of scrubland exacerbated the clear-cutting and slash-and-burn cultivation. These clearing campaigns (especially from the 1760s) had considerable consequences in terms of runoff, degrading the soil and accelerating the dynamics of erosion. The Vistre then experienced numerous overflows and carried, in periods of flooding, turbid water, causing considerable economic losses (destruction of crops and homes) and transforming landscapes (temporary cultivation of former uncultivated land of the scrubland). The history of the Vistre was also marked by major projects related to transport: in 1696, a project envisaged making the river navigable; in 1868, the covering of the Vistre was carried out in the city of Nîmes, to constitute the road of Arles. Then, in the 1950s, numerous heavy flood control measures (embankment/dyking, recalibration, protection works against specific floods, etc.) profoundly modified its course and contributed to making the Vistre a straight and narrow river, with unmarked ecological habitats. The impacts of these development policies have led to the implementation of a comprehensive water management system for the territory. In 1998, a pilot action plan was set up by the Syndicat Mixte du Bassin Versant du Vistre in order to rehabilitate the morphology and natural functioning of the watercourse, reduce the risk of flooding and reduce pollution inputs. Among the actions, the vegetation of the river banks aims to renew the socio-ecological functioning of the river, by fixing the banks and recreating buffer zones between agricultural land and the river bed. The dynamics of consultation organized around these new development policies have highlighted the need for local actors to rediscover and reappropriate the reasons that founded, over time, the development choices of previous generations. 2. Goals Global changes are disrupting the local trajectories of evolution and questioning our capacity for resilience. In a context of strong uncertainties linked to the complexity of the indicators to be taken into account (changes in temperature, precipitation, populations, environments, etc.), land-use planning policies must nevertheless make structuring choices between different adaptation and transition scenarios. This project takes its roots in the Long-Term Socio-Ecological Research framework and the Baseline Shifting approach, based on the following hypothesis: understanding the processes and factors underlying socio-ecological dynamics, and their evolution over time, may help to identify adaptation pathways for collective practices and actions. It thus provides an essential knowledge base for political decision-making, questioning the loose of perception of change occurring with the evolution of a state of reference. The proposed thesis is thus part of a participatory research and action research approach. It should contribute to a re-discovery and re-appropriation by local actors of the reasons that founded, over time, the development choices of previous generations, to consolidate and better legitimize the choice of future adaptation scenarios. 2.1. Scientific goals: - Reconstruct the environmental dynamics of the Vistre plain over time - Reconstruct the trajectory of hydro-social arrangements at work in the Vistre plain, and its transformations over a period of three centuries - Study the historicity of these hydrosocial arrangements mobilized, consciously or not, in the discursive resources of mutistakeholder dialogue around the policies of rehabilitation of the river 2.2. Territorial goals: - Achieve the most complete vision possible of the rich and complex history of socio-ecological interactions around the Vistre - Enrich the communication and information efforts of the local actors by bringing complementary insights to the local concertation in progress and to be carried out in the near future 3. Methods 3.1. Spatial scope: The research essentially concerns the historical evolution of the Vistre watershed, as well as the towns and villages that the river crosses. The PhD thesis will focus on the Vistre watershed, which is about fifteen municipalities (Bezouce, Saint-Gervasy, Marguerittes, Rodilhan, Bouillargues, Nîmes, Caissargues, Milhaud, Aubord, Bernis, Uchaud, Vestric-et-Candiac, Vergèze, Vauvert, Le Cailar, Saint-Laurent-d'Aigouze, Aigues-Mortes). Particular attention will be paid to the periods of strong evolution of the socio-ecological interactions, in connection with the great development policies and the problems encountered with the overflows of the river. 3.2. Temporal perimeter: The main part of the historical period to be covered goes back to the 18th century and the clearing campaigns which deeply marked the evolution of the river. However, certain research themes and/or environmental elements may lead the PhD student to go back to earlier periods. Spatial scope: The research essentially concerns the historical evolution of the Vistre watershed, as well as the towns and villages that the river crosses. The PhD thesis will focus on the Vistre watershed, which is about fifteen municipalities (Bezouce, Saint-Gervasy, Marguerittes, Rodilhan, Bouillargues, Nîmes, Caissargues, Milhaud, Aubord, Bernis, Uchaud, Vestric-et-Candiac, Vergèze, Vauvert, Le Cailar, Saint-Laurent-d'Aigouze, Aigues-Mortes). Particular attention will be paid to the periods of strong evolution of the socio-ecological interactions, in connection with the great development policies and the problems encountered with the overflows of the river. 3.3. Methodological approach: The PhD student will study the land use of these communal territories over the long term. He/She will of course focus on the Vistre, its riparian zone and its immediate environment. But he/she will also have to highlight the environmental dynamics for the upstream parts of the slopes (garrigues and costières) as well as the downstream part (plain). The phenomena of erosion and flooding cannot be understood if we ignore the natural and anthropic transformations that occur at the head of the slopes. The main documentation to be examined in order to understand the changes in agropastoral development and management will include, for the Ancien Régime and the 19th century, public administrative archives at different levels (intendance, military government, diocesan base, department and district, communities of inhabitants and communes) but also private archives. The archives to be visited will be mainly the departmental archives of the Gard and the municipal archives of the different communes. Some trips to extra-regional archives, in particular the national archives, will also be necessary. At the local level, the municipal deliberations, completed by surveys in some judicial and notarial archives, will allow us to better understand, according to a qualitative approach, the social and environmental issues of the Vistrenque. The computations, land registers and cadastres will provide a spatial framework for different successive periods (18th century; 1st half of the 19th century, beginning of the 20th century, middle of the 20th century and the present period). The originality of the methodological approach of this PhD thesis consists in crossing knowledge in environmental history (based on a reconstitution of socio-ecosystems and their transformation dynamics from archives) and current vernacular knowledge (based on a translation of past history in the discourses of territorial actors). The intersection of this knowledge allows for a reading of hydro-social arrangements and their appropriation in past and present discourses by local populations. It also allows us to adopt a participatory approach to research that puts the transfer of knowledge between science and society at the heart of the project, and leads to a better understanding of the choices of development made in the framework of the flood prevention program, in particular: - Reconstitution of a chrono-systemic frieze of the history of socio-ecological interactions in connection with the Vistre, based on expert testimony, consultation and analysis of archives: history of developments, history of floods, perspective with national historical events, etc. - Reconstitution of the historical memory based on a qualitative survey and participative workshops with local actors: reading of 'sedimented' landscapes, space stories, etc. - Choice of representative developments of the socio-ecological interactions at work since the 18th century in the Vistre plain which influence current representations and practices for an in-depth analysis of the historicity of hydro-social arrangements.