Flood monitoring system in the Dakar agglomeration

In recent decades, African cities have been confronted with a series of floods related to rapid urbanisation, intensification of heavy rainfall and failure of the storm drainage system. There is a growing interest in their characterisation and prediction. This study, carried out in the urban periphery of the Dakar metropolitan area, aims to propose a modelling of flows and overflows of structures at fine resolution (5m) on a pilot zone. Two methodological steps are combined to achieve this objective: 1) the construction of the urban drainage topology taking into account the modifications induced by the building, the artificial channels and the retention basins, using algorithms developed for this purpose 2) the simulations of the flows in real time or in project mode, by a parsimonious spatialized model adapted to the local context coupling a hydrological model (SCS-LR) at the scale of small basins, and a hydraulic model (Kinematic Wave) for the propagation in network of the flows produced at the outlet of the basins . The former ensures the speed of the calculation, and the latter provides precise information on the behaviour of the network in the event of flooding. The overflow points of the network are identified by the difference between the maximum flow and the capacity of the network to evacuate floods. This modelling provides sufficiently informative simulations to guide the deployment of emergency services in the field, in real time, or to evaluate the effectiveness of the facilities in project mode, in a context of limited data. The model also provides boundary conditions for applying more complex hydraulic models to determine the impact of overtopping on limited areas.