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The North Atlantic coast of Morocco has been affected historically by marine submersion events resulting from both storms and tsunamis and causing human and economic losses. The development of proactive adaptation strategies requires the study of these events over centennial to millennial timescales. Using a 2.7 m sediment core sampled from the Tahaddart estuary, we have been able to reconstruct past marine submersion events on this coastal area of Morocco over the last 4000 years. The high-resolution sedimentological and geochemical analysis conducted on this core allows us to identify 14 sediment layers attributed to marine high-energy events. The core was dated with isotopic techniques (137Cs, 210Pbex, 14C) and the outcomes reveal that three sediment layers are in connection with two major historical marine submersion events. The first layer mentioned as E1 seems to fit with the great Lisbon tsunami in 1755 CE (Common Era), an event dated for the first time on the Atlantic coast of Morocco. The other two layers referred as E13 and E14 were dated between 3464 and 2837 cal BP and correlated with marine submersion deposits found on Spanish and Moroccan coasts, which confirms the existence of a major high-energy event (around 3200 BP) similar to the one in 1755 CE. [ABSTRACT FROM AUTHOR]

The present study aims at reconstructing mid-to late Holocene paleoenvironmental evolution of the Tahaddart lower estuary (NW of Morocco) and to find possible sedimentary evidence of past marine submersion events (storm surges and tsunamis). This is achieved through the study of four sedimentary cores and by using a multiproxy approach that combines sedimentological, geochemical and foraminiferal analyses. Radioisotope measurements of 210Pb ex , 137Cs and 14C were used to provide a chronological framework of the studied cores. The results show that the Tahaddart lower estuary has evolved from a bay-like environment characterized by very shelly sandy facies (i.e., marine phase) between ∼6800 and ∼625 cal BP, to an estuarine system after ∼625 cal BP, with a dominance of fine-grained sediments (i.e., estuarine phase). We further identified several sedimentary deposits that we interpret as possible marine submersion events. Two events were identified in the marine phase at ∼3800 cal BP and ∼2700 cal BP, in coherence with previously documented marine high-energy deposits located on the Atlantic Iberian coast. In the estuarine phase of the cores, two other events were detected and dated at ∼625 cal BP and ∼200 cal BP. The latter coincides with the 1755 CE Lisbon tsunami (195 cal BP). • Four sediment cores are extracted from the Tahaddart lower estuary. • The studied area was a bay-like environment between ∼6800 and ∼625 cal BP. • Four marine submersion events are identified, including the 1755 CE Lisbon tsunami. [ABSTRACT FROM AUTHOR]

The Atlantic coast of Morocco has been exposed to marine submersion events from storm surges and tsunamis which have resulted in human and economic losses. The absence of long term records for these hazards makes it difficult to trace their behavior through time, which is the first step to prepare proactive adaptation strategies for events that may happen in the future. In this paper, we present a late Holocene record of marine submersion events along the Atlantic coast of Morocco using a 2.7 m sediment core sampled from the Tahaddart estuary. The sedimentological and geochemical analyses conducted on this geological archive showed a mud-dominated sequence with 14 allochthonous sandy layers (E1-E14) left by marine high-energy events. The deposition age of three layers (E1, E13 and E14) has been determined using conventional dating methods (210Pbex, 137Cs and 14C). The first layer, introduced as E1 seems to fit with the great Lisbon tsunami in 1755 CE (Common Era), an event dated for the first time along the Atlantic coast of Morocco. The other two layers, referred to as E13 and E14, were dated between 3464 and 2837 cal BP (calibrated years Before Present) and chronologically correlated with marine high-energy deposits found on the Spanish Atlantic coast. This correlation confirms the existence of another regional event around 3200 BP. [ABSTRACT FROM AUTHOR]

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]