As part of its flood prevention policy, the agglomeration community of the ajaccien country plans to carry out hydraulic installations as well as a retention basin on the sector located between Nicolas Peraldi Street in the south, the ring road (Boulevard Abbe Recco) in the north and the Alata road in the west. These two developments will thus absorb the hydraulic context of the sector for effective protection of the population most exposed to risks. This project consists, as a first step, of hydraulic installations of the Moulins Blancs Creek, in order to increase its capacity. This is the recalibration of the Moulins Blancs Creek from upstream of the CPAM buildings to the connection on the Arbitrone Creek. Since the Peraldi basin no longer has the main function of capping the waters of the Moulins Blancs stream, the transit of the waters of the Moulins Blancs stream through the Peraldi basin is no longer of interest. Under these conditions, it is planned to increase the capacity of the existing Moulins Blancs stream from upstream of the ring road to its confluence with the Arbitrone Creek. The solution is to develop the existing structures of the Moulins Blancs Creek to give them a capacity equivalent to the 25-year occurrence flow, i.e. 20 m 3/s. A second phase will follow (creation of a Peraldi retention basin) and will be the subject of another instruction as part of a new operation.