Sediment evolution in the mouth of the Seine estuary (France): A long-term monitoring during the last 150 years

The aim of this study is to understand the evolution of the superficial sedimentation, over the last 150 years on the mouth of the Seine estuary. An indicator is created, calculating the percentage area corresponding to the different facies for each set of available data (mid-19th century to 2009). The shift between the 1970s (16% of surface area of mud and muddy sand), the 1990s (about 50%) and 2009 (5%) appears clearly. The decrease in the muddy area is balanced with an increase of sandy mud and muddy sand surface. This evolution could be explained by river flow rate activity. The Seine estuary is a naturally tide-dominated estuary; however, engineering activities have increased the energy of the channelized river. Considering the fine-grained fraction in the superficial sediments and its variations, the Seine estuary has shifted to a river-dominated system.