Today, the hydrological function and biodiversity of riverine secondary channels are generally recognized and managers tend to protect and restore them. In this study we focused on different parapotamal meander cut-offs. Six sites were examined, two of them being impacted by gravel extraction or deepened for halieutic activity. In order to test whether systematic differences in communities occurred upstream and downstream of the different sites, temperature and dissolved oxygen concentration were continuously monitored, other physical and chemical data were monthly measured and benthic macroinvertebrates were sampled in two seasons. Related to the abiotic data, in each site, water exchanges occurred between the river and / or the groundwater. In the unmodified sites, those few silted up displayed the greatest biodiversity with numerous EPT (Ephemeroptera, Plecoptera and Trichoptera) while in those largely silted, the habitat homogeneity induced a low biodiversity. In the two impacted sites, the upstream modification enhanced natural silting and few EPT were present while in the site largely open to the river, water quality, diversity and EPT richness remained high.