Figure 18 - uploaded by Laurent Pascal Diémé
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Carte de production (a) et d'aptitude à l'accumulation (b) du ruissellement dans la région cévenole, France (Bonnet, 2012). Au final la méthode permet de définir spatialement, par simple analyse des caractéristiques de surface, les zones les plus propices au ruissellement sur un territoire. La méthode n'intègre cependant pas les caractéristiques des événements pluvieux à l'origine du ruissellement. Ce qui fait dire à Lagadec (2017) que c'est une méthode « sèche ». Néanmoins Breil et al. (2017) indiquent que la méthode IRIP peut être considérée opérationnelle pour pré-identifier des zones à risque d'inondation par ruissellement intense, où des études et modèles plus physiques devraient être appliqués pour dimensionner des réponses de gestion.
Source publication
In recent decades, African cities have been confronted with a series of floods linked to the rapid and poorly managed urbanisation, the intensification of heavy rains and the failure of the rainwater drainage system. Faced with this situation, protection against the risk of flooding is a major development issue. Increasing interest is being shown i...
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Green Infrastructures as Best Management Practice (GI-BMP) play important role in preserving cities from urban flood and excessive runoff. In the process of using GI-BMP in cities for stormwater management, a number of steps are taken that normally include selection of suitable sites, formulating proper combination of infrastructures, and optimizat...
Citations
With the recurrence of flooding in African cities, there is growing interest in the development of sufficiently informative tools to help characterize and predict overflow risks. One of the challenges is to develop methods that strike a compromise between the accuracy of simulations, the availability of basic data, and the shortening of calculation times to be compatible with real-time applications. The present study, carried out on the urban outskirts of Dakar, aims to propose a method capable of modeling flows at fine resolution (5 m2), over the entire area, and providing a rapid diagnosis of how the drainage network is operating for rainfall intensities of different return periods, while taking urban conditions into account. Three methodological steps are combined to achieve this objective: i) determination of drainage directions, including modifications induced by buildings, artificial drainage and storage basins, ii) application of a hydrological model for calculating flows at the outlets of elementary catchment, iii) the implementation of a hydraulic model for propagating these flows through the drainage network and a storage model for retention basins. The network overflow points are calculated as the difference between the calculated flows and the network’s capacity to evacuate them. Simulation results show that the stormwater drainage network is capable of evacuating runoff volumes generated by rainfall with a low return period (10 years), but seems to overflow for rainfall with a rare frequency (100 years), with overflow rates sometimes exceeding 18 m3/s. The model, built on the ATHYS modelling platform, also provides boundary conditions for applying more complex hydraulic models to determine the local impact of drainage network overflows on limited areas.
