The objective of the operation is to limit the flows of the Camplanier cadereau so that they are compatible with the capacity of the framework works of the Dense Urban Zone, allowing underground transit without overflowing the cadereau. The construction of the Méjean dam contributes to increase the upstream retention capacities as well as the hydraulic installations of the Camplanier cadereau at the level of the Chemin du Grand Bois to increase the capacity before overflow to 12m3/s