This work describes the innovative methodology used to define the sewersheds (domestic and pluvial) for sediments accumulated in each silt trap in the Paris sewerage network.
The method is automated as far as possible, but involves four stages of manual intervention. These sewersheds serve two purposes: 1) to define the houses and buildings (shops, restaurants, offices, etc.) served by each treatment silt trap; 2) to define the surface area served (sewershed), considering not only the houses and buildings but also parks/gardens and pavements. This study allowed us to distinguish two types of system for the sewerage network: 1) Dry Weather system, where wastewater flows through a reduced number of sections, as the water line remains below the thresholds of effluent-free sections; 2) Rainy Weather system, where the water line exceeds the thresholds. Combined sewage flows through a greater number of sections to prevent surface overflows. Then, the particular arrangement of the silt trap in relation to each other was also highlighted. The silt traps are arranged in a sedimentation cascade, with some downstream of others.
45 of the 159 silt traps were selected to correspond unambiguously to the targeted problems. These are the 45 silt traps that have no upstream basin. The sewersheds of these 45 silt traps was defined. This delimited area is a new scientific object that will then be used to select, at the scale of interest for our study, all the external spatial data relating to each silt trap, such as those provided by the French national institute for statistical and economic studies, the Paris Urbanism Agency, etc
Reference: Asselin, C., Jacob, J., Moilleron, R., Rican, S., 2024. Approche méthodologique pour la cartographie des zones d’apport de sédiments dans le réseau d’assainissement parisien. Techniques Sciences Méthodes n°6, 2024.