Fluvial sediment transport degradation after dam construction in North Africa.

Recent reductions of sediment transport are observed in Bouregreg River and estuary close to the city of Rabat in Morocco. The cause of this evolution in sediment transport which may be due to human activities (dam, pollution), climate variability and natural events has been investigated from a paleo-hydrological approach. Sedimentological and geochemical analyses of slackwater flood deposits are used to assess the impact of a dam installed in 1974 and the climate change on the evolution of sediment transport during about 60 years. Higher accumulation rate of about 3,64 cm/year is observed between 1950 and 1978, whereas it was much lower about 0,41 cm/year between 1990 and 2017. This strong decrease in sediment rate appears much more due to the impact of dam construction rather than to climate change, however climate change in an increasing concern for the future. • The paleo-hydrology is an excellent approach to estimate the impact of dam and climate change on fluvial sediment transport. • One potential climatic driver of river discharge in Morocco is the North Atlantic Oscillation (NAO). • Recent reduction of sediment transport is observed in Bouregreg River in Morocco, after the construction of dam since 1974. • Strong decrease in sediment rate appears much more due to dam effect than to climate change. [ABSTRACT FROM AUTHOR]