The Loire, the last wild river in Western Europe, undergoes recurrent maintenance operations of bed to improve flow and to avoid reduction of the main stem. In autumn 2012, the territorial collectivities carried out levelling of one island in the Natural Reserve of Saint-Mesmin (Centre region, France). We took advantage of this work to launch a long term survey of the island recolonization by plants, birds, beavers and insects. We report here the impact on insect populations taking ground beetles (Coleoptera : Carabidae) as a model. We compared species (communities) before and just after the levelling.