1-D modelling of side weir CSOs

In western European cities, side weir Combined Sewer Overflows represent one of the main sources of pollutants rejected in water bodies. These devices, being in most cases difficult to control, have a hydraulic behaviour difficult to assess. The use of numerical model is thus a necessary alternative technique. However, the coupling of classical side weirs models with usual hydrodynamic models turns out actually impossible. In this paper; we investigate the features of a new side weir model. adapted to the hydrodynamic representation of urban drainage systems. This model, called "dissociated model", allows to account for the variation of water depth along the side weir in a simplified way while being compatible with the 1-D Saint Venant equations.