Lowland gravel-bed river recovery through former mining reaches, the key role of sand

Whereas the geomorphic effects of in-channel mining have been widely documented, very few studies focused on recovery trajectories after ended. This paper describes and quantifies channel adjustment extended over-widened pits located in a low energy gravel-bed river, identifies factors that control their rate. The study was based aerial photographs LiDAR analysis, grain-size sampling, bedload computation geophysical measurements made during ground penetrating radar (GPR) electrical resistivity tomography (ERT) surveys. We describe spatio-temporal changes morphology former as well current surficial longitudinal pattern neighbouring upstream downstream reaches. Our results show wide range readjustments. Between 23 47 yr end mining, reaches still not yet fully recovered. planimetric rate is closely correlated with ratio volume deposited to original volume. Finally, infilled material only partly composed mainly sandy fine sediments play primary role process. abundance sand, controlled by lithology watershed, explains unexpectedly high rates some despite river. • Characterisation morphological Adjustment underway 27–47 years stopped Recovery pit volume, sediment supplied trap efficiency sand load plays an essential processes Catchment also crucial