| Abstract |
The Scorff, a coastal river in the southwestern Armorican Massif, is suspected of becoming over-sanded in recent decades, similar to many other rivers with granitic watersheds. This project, funded and co-led by the MIAME cluster (OFB-INRAE-Institut Agro-UPPA) and LETG, first analyzes spatial relationships between the potential sand production from various sub-watersheds and the rate of sand coverage on flow facies along the river that are suitable for colonization by the sea lamprey. The evolution of these parameters over the past two decades is also examined. Finally, the project explores the potential effects of excessive sandy sediment deposits on sea lamprey spawning grounds. The distribution of sand was found to be primarily influenced by slope and the presence of numerous transverse structures, with localized exacerbation due to complex factors. For example, the Kerustang sub-basin is highly susceptible to sand erosion, and after the opening of the Pont-Calleck dam (13th century) in 2011, it has contributed a substantial sand load. Observations of spawning ground locations over the past decade suggest that, for now, these sand deposits have not reduced the availability of favorable habitats. |