Reconstruction and simplification of the Greater Paris sewerage network

In order to mitigate negative urbanization effects on urban water management, nature based solutions (NBS) are often recommended. Some of them can also be recommended to improve thermal comfort, inhabitants well-being, their security, ... They can also take part in climate change adaptation strategies. A more systemic evaluation of such solutions is then becoming essential. The hydro-climatic model TEB-Hydro has been developed in order to evaluate urban planning projects, regarding urban water management and thermal comfort, at the City scale. TEB-Hydro model, based on a regular mesh grid, needs to know the water different paths (at the surface, inside the stormwater or combined network, into the ground). An automatic tool (TOHR) has been developed, from urban data banks, to build an oriented graph of the different water flows, that is then projected on TEB-Hydro grid, to provide to the model all the parameters needed for routing calculation. This oriented graph is based on the stormwater, waste water, combined and natural networks. Thus, it allows the reconstruction of a complete network, by taking into account all the different water flows. Nonetheless, this rebuilt network has to be simplified, in order to be adapted to the grid spatial resolution. The reconstruction result, at the Greater Paris scale is globally satisfying. Numerous errors are due to wrong connections, but at a fine scale. The flow path is then a bit longer than in the reality. The larger difficulties are over Paris where the network is a crossroad with numerous meshes. The reconstruction of the separate system is better as it is less meshed than the combined one. And even on the combined system, realistic large drained areas defined at different points on the network are obtained. Then the reconstructed network is available for hydrologic simulations.