The November, 1st, 1755 Tsunami in Morocco: Can Numerical Modeling Clarify the Uncertainties of Historical Reports?

International audienc

Heavy metal content and potential ecological risk assessment of sediments from Khnifiss Lagoon National Park (Morocco)

Coastal lagoons are important but sensitive environments, being transitional zones between land and sea. The Khnifiss lagoon is the most important desert wetland in Morocco, but little data have been produced concerning heavy metal geochemistry and enrichments in the sediments. Therefore, 26 surface sediments (15 intertidal and 11 subtidal) and 2 sediment cores were collected in 2016 and analyzed for a selection of heavy metals. The data were processed to assess the degree of contamination and the corresponding potential ecological risk, using several accumulation/enrichment indices, and the singular and multi-metal risk indices. Mean concentrations in the bottom layers of the two cores, dating from a pre-industrial age according to geochronological analysis, were used as the local geochemical background. The resulting values were on the whole lower than those reported for other areas of the northeastern coast of Morocco. Multivariate statistics were also applied to better understand relationships among variables (metals and other geochemical parameters) and to reveal similarities among sample groups. The results showed that, although the lagoon is not yet affected by significant anthropogenic influences, small enrichments can be recognized, especially for Ni and Cd. The cause may be related to the proximity to the main national highway, the vehicles and machinery used in the saltworks located in the area, and the small harbors used principally for fishing. In addition, industrial emissions from the Atlantic coast of Morocco and adjacent countries can be reasonably attributed as additional contributors to the enrichments. In terms of potential ecological risk, Cd shows the greatest impact compared to the other metals investigated

Sedimentary records of anthropogenic contribution to heavy metal content in Oum Er Bia estuary (Morocco)

International audienceLevels of heavy metals (Cd, Hg, Cr, Cu, Fe, Mn, Ni, Pb and Zn), organic carbon content and textural characteristics in the superficial and cored sediments of Oum Er Bia estuary have been studied. The anthropogenic fluxes of heavy metals were determined in two sediment cores collected in the estuary, facing urban sewages. A dated estuarine core from the inter-tidal area was assessed using 210Pb and 137Cs data. These data indicate that the mean sedimentation rates are 0.38–68 cm year-1. The analytical results and the radio-dating of sediment cores show extremely high concentrations of Zn, Pb and Cu in the sediments that can be ascribed mostly to the discharge of the liquid effluent from the sewage since the late 1960s, decreasing towards the present day. The pollution intensity of the estuary is determined by the enrichment factors, which show that the Oum Er Bia estuary is moderately polluted to polluted

IMPACT OF THE PORT STRUCTURE IN THE SPATIO-TEMPORAL EVOLUTION OF THE SEDIMENTARY AND BATHYMETRIC CHARACTERISTICS OF A MOROCCAN ATLANTIC BAY, STUDY CASE BAY OF SAFI CITY

Abstract. This study focuses on morpho-sedimentary changes in the bay of Safi (Atlantic coast of Morocco), due to a progressive extension of the port. For this purpose, several bathymetric and sedimentary surveys carried out by the Hydrographic and Oceanographic Service of the Navy (SHOM) in 1892, 1906 and 1940 respectively, coupled with a bathymetric and sedimentary measurement mission in 2009, were analyzed to understand the impact of the port developments on the bottom of Safi Bay. This analysis consists of making maps of the evolution of (i) sedimentary facies (of different dates 1892, 1906, 1940 and 2009) and (ii) the shallow seabed of the three periods 1892–1906, 1906–1940 and 1940–2009. The sedimentary facies maps show that the facies appear unstable and evolve intermittently in response to environmental changes in the bay (port construction and expansion). In addition, the overlay of the bathymetric maps indicates that the bay has undergone changes (lowering, stability, and raising) controlled by hydrodynamic conditions before, during, and even after harbor construction. Analysis of the data showed that the expansion of the port often reshaped the morphology of the bay's seabed. The consequences of these evolutions are the appearance of the fattening or the erosion of the bank and the filling of small depressions of sediments. This evolution is reflected in the modification of the funds near the port and the beach of Safi. </jats:p

STUDY OF MORPHODYNAMIC AND SEDIMENTOLOGICAL CHANGES IN THE OUALIDIA LAGOON (MOROCCO) USING BATHYMETRIC DATA: FIRST INVESTIGATIONS AFTER THE SEDIMENT TRAP DREDGING

Abstract. Coastal lagoons are highly dynamic and physically complicated systems. They are environmentally productive and socio-economically valuable. Contemporary global development and management pressures require a better understanding of their dynamics and sustainability. The present study focuses on the problem of water confinement in the Oualidia lagoon (Atlantic coast of Morocco). This lagoon is characterized by an asymmetric tidal propagation, with a shorter duration of the flood (rising tide) than the ebb (falling tide). In the long term, this contributes to the reduction of depths and the confinement of water upstream. After extensive studies, a sediment trap was created in 2011 to trap the finest sediment in the upstream part of the lagoon. This study aims to analyze the morphodynamical and sedimentological changes in the lagoon of Oualidia, after the sediment trap dredging. For this purpose, bathymetric surveys covering 6 years between 2006 and 2012 were analyzed, providing sufficient data to identify the morphological changes that the lagoon has undergone during this period. The data analysis was followed by a study of the lagoon bed dynamics using profile lines extracted from the bathymetric data in a GIS environment. As a result, the findings partly show that over 6 years, an average height of +0.65 m was gained by the lagoon, while the average change in the eroded areas was estimated to be −0.42 m. In addition, the eroded area in the lagoon was estimated to be about 1,513,800 m2 with an erosion volume of 633,383 m3, while the accumulated area found was about 2,699,396 m2 with an accumulation volume of 1,765,866 m3. These changes can be related to the large input of marine sediment, mainly caused by tidal currents and waves, but also to the creation of a sediment trap in the upstream area of the lagoon. </jats:p

A long-term record of land use change impacts on sediments in Oualidia lagoon, Morocco

International audienceAn integrated approach, involving land use patterns and heavy metal contents of the surficial and cored sediment,was proposed to detect the characteristic spatial and temporal scale of point and non-point source humandisturbances on the Oualidia lagoon in Morocco. Identification and description of the temporal and spatialdistributions of the main contamination sources of heavy metals are analyzed using statistics and GIS methods.The results show that surficial sediments are highly enriched in heavy metals compared to their preindustrialbackground levels. Land-use types affected lagoon sediment pollution in different ways: 1) agricultural areas hadthe highest potential for sediment contamination by heavy metals, particularly Pb, Cu and Hg, 2) Ni and Cr are themain pollutants originating from urban sewage and 3) oyster farming and traditional land uses such as salt flats,pastures showed low levels of others metals. The enrichment factors (normalized by Al) obtained from thesediment cores indicated that the lagoon is (strongly/moderately) polluted by all metals which were attributed toagricultural activities and wastewater discharges from urbanized areas

Biomonitoring environmental status in semi-enclosed coastal ecosystems using Zostera noltei meadows

Semi enclosed waters, such as estuaries and lagoons, are vulnerable ecosystems that are experiencing persistent trace element (TE) contamination. Seagrasses have been reported worldwide as valuable bioindicator species for coastal contamination monitoring purpose. This is, to our knowledge, the first time the TE contamination of semi-enclosed ecosystems has been monitored along the full latitudinal gradient of the Moroccan Atlantic coast. In these ecosystems, the dominant seagrass species is Zostera noltei. 23 TEs (Fe, Al, Cr, Mn, Co, Ni, V, Cu, Zn, Sr, Li, As, Ag, Cd, Sn, Sb, Mo, Ba, Ti, Pb, U, Bi and Hg) and four major elements (Na, Mg, K, Ca) were measured in sediments and seagrass leaf samples were collected upstream and downstream of five semi-enclosed areas. They contrasted in both climatic conditions and levels of environmental contamination. The Trace Element Pollution Index (TEPI) and the Trace Element Spatial Variation Index (TESVI) were calculated from chemical element concentrations in the samples. Of the five semi-enclosed areas, Sidi Moussa lagoon's sediments were the most contaminated (TEPI = 1.18). The TESVI differed highly between chemical elements among the five water bodies for sediments and seagrass leaves, the highest spatial variability being for Ag (TESVI = 72.01 and 21.05 respectively). For Z. noltei leaves, a latitudinal gradient of TE accumulation was recorded. A high bioconcentration factor (BCF > 1) for Cd, Mo, Sb, Ag, Zn and U indicated that the sediments were efficiently uptaken by the seagrass. Significant correlations (p < 0.05) between levels of Cd, Ag, Fe, Al, Ba, Hg, Mn and Zn in sediments and in Z. noltei leaves indicated similar contamination occurrences in both environmental matrices and their bioavailability for seagrasses. Overall, leaf TE bioconcentration among and within the study sites resulted from differences in element bioavailability and environmental conditions (climatic context, hydrological conditions and human impact). Ultimately, Z. noltei is a useful bioindicator of Cd, Mo, Sb, Ag, Zn, U, Al, Fe, Mn, Ba and Hg contamination in sediments. © 2019 Elsevier Lt

Performance of coastal sea-defense infrastructure at El Jadida (Morocco) against tsunami threat: lessons learned from the Japanese 11 March 2011 tsunami

This paper seeks to investigate the effectiveness of sea-defense structures in preventing/reducing the tsunami overtopping as well as evaluating the resulting tsunami impact at El Jadida, Morocco. Different tsunami wave conditions are generated by considering various earthquake scenarios of magnitudes ranging from <i>M</i>_w = 8.0 to <i>M</i>_w = 8.6. These scenarios represent the main active earthquake faults in the SW Iberia margin and are consistent with two past events that generated tsunamis along the Atlantic coast of Morocco. The behaviour of incident tsunami waves when interacting with coastal infrastructures is analysed on the basis of numerical simulations of near-shore tsunami waves' propagation. Tsunami impact at the affected site is assessed through computing inundation and current velocity using a high-resolution digital terrain model that incorporates bathymetric, topographic and coastal structures data. Results, in terms of near-shore tsunami propagation snapshots, waves' interaction with coastal barriers, and spatial distributions of flow depths and speeds, are presented and discussed in light of what was observed during the 2011 Tohoku-oki tsunami. Predicted results show different levels of impact that different tsunami wave conditions could generate in the region. Existing coastal barriers around the El Jadida harbour succeeded in reflecting relatively small waves generated by some scenarios, but failed in preventing the overtopping caused by waves from others. Considering the scenario highly impacting the El Jadida coast, significant inundations are computed at the sandy beach and unprotected areas. The modelled dramatic tsunami impact in the region shows the need for additional tsunami standards not only for sea-defense structures but also for the coastal dwellings and houses to provide potential in-place evacuation

Geographic Information System for Integrated Coastal Zone Management in Developing countries: cases studies in Mauritania, Côte d'Ivoire, Guinea-Bissau and Morocco.

372Despite leadership of developed country in GIS field and ICZM field, ICZM and GIS together have been compared to a puzzle. This involves questioning on capacity to put together such ICZM and GIS in developing country. We focus on four of such developing countries to highlight difficulties to understand and to manage costal area with the use og GIS. Sustainable management of coastal areas is critical to the long-term health, safety and welfare of many african comunities of these (and other) countries. Despite their importance, coastal zones are being modified or reclaimed, often driven by economic and financial motives. Coastal management offers the opportunity to illustrate the use of GIS and related spatial information technologies not only on coastal issues but in the broader arena of land use planning. The aim of this contribution is to review, synthesize and analyse experiences on coastal management along coasts of Mauritania, Côte d'Ivoire, Guinea-Bissau and Morocco. This allows us to rank these countries from country with a huge lack of geographical information to country with a lead in GIS technology coupled with a good approach of ICZM. The place of developed countries in this rank is also taken into account

Geographic Information System for Integrated Coastal Zone Management in Developing countries: cases studies in Mauritania, Côte d'Ivoire, Guinea-Bissau and Morocco.

372International audienceDespite leadership of developed country in GIS field and ICZM field, ICZM and GIS together have been compared to a puzzle. This involves questioning on capacity to put together such ICZM and GIS in developing country. We focus on four of such developing countries to highlight difficulties to understand and to manage costal area with the use og GIS. Sustainable management of coastal areas is critical to the long-term health, safety and welfare of many african comunities of these (and other) countries. Despite their importance, coastal zones are being modified or reclaimed, often driven by economic and financial motives. Coastal management offers the opportunity to illustrate the use of GIS and related spatial information technologies not only on coastal issues but in the broader arena of land use planning. The aim of this contribution is to review, synthesize and analyse experiences on coastal management along coasts of Mauritania, Côte d'Ivoire, Guinea-Bissau and Morocco. This allows us to rank these countries from country with a huge lack of geographical information to country with a lead in GIS technology coupled with a good approach of ICZM. The place of developed countries in this rank is also taken into account