How do instream flow increase and gravel augmentation impact biological communities in large rivers: A case study on the Upper Rhine River

• DOI: 10.1002/rra.3237
• Publication Date: 2018-01-10T13:45:49Z
• Authors: C. Staentzel; F. Arnaud; I. Combroux; L. Schmitt; M. Trémolières; C. Grac; H. Piégay; A. Barillier; V. Chardon; J.‐N. Beisel
• Keywords: 0106 biological sciences; 330; Invasive species; Rhine; [SDE.IE]Environmental Sciences/Environmental Engineering; [SHS.GEO] Humanities and Social Sciences/Geography; macroinvertebrates; [SHS.GEO]Humanities and Social Sciences/Geography; Biodiversity; 15. Life on land; Large rivers; Riparian plants; 01 natural sciences; 6. Clean water; 12. Responsible consumption; [SDE.BE] Environmental Sciences/Biodiversity and Ecology; 13. Climate action; [SDE.ES] Environmental Sciences/Environment and Society; 14. Life underwater; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDE.ES]Environmental Sciences/Environment and Society; Ecological restoration

AbstractActions are being developed to address the adverse consequences of engineering works on large European rivers by developing and implementing restoration activities in order to enhance the functionality and biodiversity of fluvial hydrosystems. However, as has frequently been mentioned in the scientific literature, quantitative and qualitative evaluation of the project benefits, if any, and their sustainability are hindered by the difficulty in assessing the responses of aquatic and riparian communities to the methods employed. A case study was conducted on a by‐passed section of the Upper Rhine River (France and Germany) to investigate the effects of instream flow increase and gravel augmentation on selected aquatic and riparian communities (macroinvertebrates, macrophytes, and riparian plants). This paper presents the results of a 6‐year interdisciplinary, before‐after control‐impact design monitoring study. The complexity of the study lies in carrying out a separate assessment of the cumulative effects on a site‐based, project‐specific basis. The results showed that (a) the instream flow increase resulted in greater richness of macrophyte species in the newly created backwaters, (b) the artificial gravel bar favoured the recruitment of pioneer species, including invasive species, although gravel redistribution by floods prevented their development, and (c) gravel augmentation tended to promote the taxonomic richness of macroinvertebrate communities with the appearance of species adapted to the new substrate areas. These findings should help to fill the knowledge gaps in large‐scale restoration and contribute key responses to the most frequently arising issues in this area, especially those concerning the efficiency and sustainability of river restoration projects.