The Etoile dams on the Nièvre (Referential of Obstacles à l’Ecoulement -ROE- 21218) and Bavelincourt (ROE 21218) and Querrieu (ROE 29369) on the Hallue hinder ecological and sedimentary continuity, given the height of their residual falls at 1.30 metres, 1.10 metres and 80 centimetres. The Somme River and its tributaries are home to significant aquatic biodiversity (RAMSAR site) and are recognised as streams for highly amphihalin migrants (fish living both in rivers and at sea). These include aloses, eels, salmon, sea trout and sea lamprey. Some of these species are threatened with extinction. The restoration of hydro-ecological continuity is an important issue in reclaiming the quality of rivers in the Somme Basin, including the Allue and Nièvre, which are fragmented and artificialised. The objective of the work is to remove these three blockages in order to give access to spawning areas of the basin head to fish species and to restore natural dynamics to flows.