Les rôles paysagers et écologiques des bras-morts - Étude de cas du Haut-Escaut en Belgique

Abstract

This work follows the concerns raised by the River contract Escaut-Lys. In fact, this one sets out the loss of lateral functioning of the watercourse as a problem. This loss has direct impact on the land arround riverbed which constitutes areas of erosion, overflow and water exchange (alluvial groundwater). They contribute in all aspects to the proper functioning of the watercourse as well as to the survival of animal and plant species dependent on the associated phenomena (CR Escaut-Lys, 2019). The way envisaged by the River Contract to improve the functioning and condition of aquatic environments consists above all in defining and preserving the freedom of watercourses, then setting up targeted operations in an objective of environmental enrichment. This program cannot be carried out without raising awareness and educating residents, managers and users of waterways.

Two anthropogenic pressures are therefore exerted on the entity that constitutes the Scheldt. First, an internal pressure by the use of the river for navigation which forces it into a fixed and uniform appearance, requiring the sinking of the bed and the erection of dykes. In a second step, external pressure by the conversion of its floodplain into cropland, which requires the drying of land and wetlands and deprives the river of these alluvial overflow meadows.

This work therefore attempts to highlight the roles played by wetlands such as the oxbows that line the waterways and to what extent their preservation is important above all for ecological objectives. To do this, this work will make an inventory of the oxbows present along the Scheldt in Wallonia by evaluating them using a landscape approach and an ecosystem approach. This second will be done through an analysis of the ecological network of the Upper Scheldt valley in which the oxbows are part and an analysis of the ecosystem services provided by them.

Ultimately, this work proposes various courses of action for the management and maintenance of the Scheldt’s oxbows in the Walloon region to strengthen their role within the ecological network of the valley and to preserve the last witness fragments of the humid landscape of the Scheldt valley.

By questioning the future of wetland landscapes against the need for the use of the river and the exploitation of land, this thesis contributes on its own scale to the knowledge of the existence and importance of the environments constituted by the oxbows. This duality between ecological issue and economic issue being often observed makes it an interesting subject within Landscape Architecture studies.