Harbours need to maintain a sufficient water column to allow good navigation. Dredged sediment may be deposited at sea. Nevertheless, they may have different physical and chemical characteristics compared with the sediment in place which generate multiple effects on the benthic environment. Studies on the impacts of such eco-environmental disruptions are numerous and necessary. Unfortunately, no sampling schedule patterns have been proposed despite the OSPAR Convention (www.ospar.org) covering Northwest Europe, and the London Convention (http://londonprotocol.imo.org), neither of which impose a "uniform" design for monitoring programmes. What is the best way of measuring sediment cover around a site used for dumping to obtaining the best representation of the sediment coverage? In the eastern Bay of Seine (France), sediment management and dredging practices (" Grand Port Maritime " Rouen and Le Havre) constitute one of the main anthropic pressure and driving factors in the morphological evolution of the Seine estuary and its sedimentary hydrodynamics. This study is focused on the environment surrounding the Octeville dumping site (used by the " Grand Port Maritime du Havre ").