76 research outputs found
Identifying success factors for integrated coastal zone management:Development of a regional coastal plan in Morocco
No full textIntegrated coastal zone management (ICZM) is a policy framework that aims to achieve sustainable development in the context of limited space and resources of (densely populated) coastal areas, by balancing environmental protection, societal needs, and economic development. In this paper, we first reflect on key components influencing the success of ICZM. Second, we compare our understanding to the process of preparation of a coastal plan for the Tangier-Tetouan-Al Hoceima region in Morocco. Finally, we extend and generalize our conclusions to ICZM as a relevant policy framework, by identifying factors that influence the context-specific interpretation of ICZM in Morocco. We argue that ICZM depends on the integration, implementation, coordination between science and policy, and appropriate governance. In the Moroccan case, a variety of institutions first need to agree on the governance structure and priorities, as a base for a clear direction for the regional ICZM. This calls for a change of stakeholder engagement for certain steering institutions and leadership by ‘wilaya’. The coastal plan preparation process showed a lack of balance between stakeholder participation and institutional coordination, and increased bureaucratization which covers accountability for decision-making. Although coastal governance is supported by the national government, it is still unknown to what extent it is supported at the regional level which oversees the ICZM. We conclude that besides leadership, political support, and institutional commitment, broader stakeholder engagement is crucial for the decisions that shape the future of the coastal zone, which indicates that governance is the most important success factor for ICZM.</p
Géodynamique actuelle du bassin versant de l'Oued Tensift (Maroc) : érosion mécanique et bilan des transports solides fluviaux. / Present geodynamic of the Tensift drainage basin (Morocco) : mechanical erosion and fluvial transports of sediments
No full textPresent geodynamic of the Tensift drainage basin (Morocco) : mechanical erosion and fluvial transports of sediments
The aim of this study is to improve the knowledge on sediment mobilization in semi-arid climate through a global estimation of erosion-transport-sedimentation budget in the Tensift drainage basin (Morocco).
The lithological material which could be mobilized by erosion of the main formations has been estimated using simple models to a specific value of 373 t.km-2.an-1. Sediment discharge to Atlantic ocean is calculated using river transport measurements to 200 t.km-2.an-1. This last flux represents 69% of the total sediments potentially eroded in the Tensift basin. The remaining 31% could be attributed to sedimentary deposits in the alluvial plain.
The comparison between the fluvial transports of different floods during the same year exhibits the importance of the hydrological processes in the mechanical erosion control. Moreover, a survey of three hydrological years (dry. mean and humid) allows to follow the present interannual geodynamic evolution of this basin. The sediment budget shows that the climatic factor controls the fluvial transport for the different lithologies. Topography and lithology represent complementary factors, mainly in mountainous part of the drainage basin. Replaced in the whole Maghreb context, the mean values calculated for the Tensift river are in good agreement with those already obtained by various authors (Snoussi et al., 1989 et 1990 ; Probst et Amiotte Suchet, 1992) regarding moroccan. algerian and tunisian rivers. This study confirms the importance of the mechanical erosion and fluvial sediment transports in semi-arid climatic area such as the Tensift draining basin. The sediment yield measured in this region are for example much more higher (1 to 2 order of magnitude) than those observed in tropical Africa.L'objectif de cette étude est de contribuer à une meilleure connaissance des processus de mobilisation des matières solides en zone semi-aride à partir d'une estimation globale du bilan érosion-transport-sédimentation sur le bassin versant du Tensift (Maroc).
Les matériaux théoriquement mobilisables par l'érosion des principales formations lithologiques du bassin versant (formations alumino-silicatées et carbonatées) sont estimés à partir de modèles simples et correspondent à un tonnage spécifique moyen d'environ 373 t. km-2. an-1. L'exportation de ces matériaux vers l'océan Atlantique est estimée à partir des mesures de transports solides à 200 t.km-2.an-1 en moyenne. Ce flux correspond à 69% du flux théorique de particules potentiellement érodées sur le bassin versant. Les 31% qui restent peuvent être attribués à l'alluvionnement dans la plaine.
La comparaison des transports solides fluviaux au cours des différentes crues d'une même année met en évidence l'importance des processus hydrologiques dans le contrôle des phénomènes d'érosion mécanique. De même, une étude menée sur trois années hydrologiques différentes (sèche, moyenne et humide) permet de suivre l'évolution de la géodynamique actuelle dans ce bassin à l'échelle interannuelle. Les résultats ainsi obtenus permettent d'établir le bilan de l'érosion mécanique aux échelles saisonnière, annuelle et interannuelle. Ce bilan traduit en premier lieu le contrôle du climat et par conséquent de l'hydrologie sur la quantité des apports : la topographie et la lithologie interviennent en synergie dès lors que les formations les plus facilement érodables se situent en zone de montagne.
Replacé dans le contexte maghrébin, le Tensift montre en moyenne des résultats qui semblent en accord avec ceux obtenus par d'autres auteurs (Snoussi et al.. 1989. 1990 ; Probst et Amiotte Suchet. 1992) pour des oueds marocains. algériens et tunisiens. Par contre dans le contexte africain, les tonnages spécifiques du Tensift sont nettement supérieurs (1 à 2 ordres de grandeur) à ceux observés en Afrique tropicale.Haida Souad, Snoussi Maria, Latouche Claude, Probst J.L. Géodynamique actuelle du bassin versant de l'Oued Tensift (Maroc) : érosion mécanique et bilan des transports solides fluviaux. / Present geodynamic of the Tensift drainage basin (Morocco) : mechanical erosion and fluvial transports of sediments. In: Sciences Géologiques. Bulletin, tome 49, n°1-4, 1996. Fleuves et érosion, sous la direction de Jean-Luc Probst . pp. 7-23
First Mediterranean Assessment Report – Chapter 1: Introduction
No full textThe Chapter 1: Introduction of the First Mediterranean Assessment Report (MAR1) published by MedECC in November 2020 sets up the scope and objectives of the Assessment Report from What do we know about the Mediterranean Basin and what do we need to know? to the Principles and processes of work in MedECC.Preferred Citation: Lange MA, Llasat MC, Snoussi M, Graves A, Le Tellier J, Queralt A, Vagliasindi GM 2020 Introduction. In: Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer W, Guiot J, Marini K (eds.)] Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, France, pp. 41-58, doi:10.5281/zenodo.7100592
Géodynamique actuelle du bassin versant de l'Oued Tensift (Maroc) : érosion mécanique et bilan des transports solides fluviaux. / Present geodynamic of the Tensift drainage basin (Morocco) : mechanical erosion and fluvial transports of sediments
No full textPresent geodynamic of the Tensift drainage basin (Morocco) : mechanical erosion and fluvial transports of sediments
The aim of this study is to improve the knowledge on sediment mobilization in semi-arid climate through a global estimation of erosion-transport-sedimentation budget in the Tensift drainage basin (Morocco).
The lithological material which could be mobilized by erosion of the main formations has been estimated using simple models to a specific value of 373 t.km-2.an-1. Sediment discharge to Atlantic ocean is calculated using river transport measurements to 200 t.km-2.an-1. This last flux represents 69% of the total sediments potentially eroded in the Tensift basin. The remaining 31% could be attributed to sedimentary deposits in the alluvial plain.
The comparison between the fluvial transports of different floods during the same year exhibits the importance of the hydrological processes in the mechanical erosion control. Moreover, a survey of three hydrological years (dry. mean and humid) allows to follow the present interannual geodynamic evolution of this basin. The sediment budget shows that the climatic factor controls the fluvial transport for the different lithologies. Topography and lithology represent complementary factors, mainly in mountainous part of the drainage basin. Replaced in the whole Maghreb context, the mean values calculated for the Tensift river are in good agreement with those already obtained by various authors (Snoussi et al., 1989 et 1990 ; Probst et Amiotte Suchet, 1992) regarding moroccan. algerian and tunisian rivers. This study confirms the importance of the mechanical erosion and fluvial sediment transports in semi-arid climatic area such as the Tensift draining basin. The sediment yield measured in this region are for example much more higher (1 to 2 order of magnitude) than those observed in tropical Africa.</jats:p
Géodynamique actuelle du bassin versant de l'Oued Tensift (Maroc) : Erosion mécanique et bilan des transports solides fluviaux
No full textL’objectif de cette étude est de contribuer à une meilleure connaissance des processus de mobilisation des matières solides en zone semi-aride à partir d’une estimation globale du bilan érosion-transport-sédimentation sur le bassin versant du Tensift (Maroc).
Les matériaux théoriquement mobilisables par l’érosion des principales formations lithologiques du bassin versant (formation alumino-silicatées et carbonatées) sont estimés à partir de modèles simples et correspondent à un tonnage spécifique moyen d’environ 373 t.km-2. an.-1. L’exportation de ces matériaux vers l’océan Atlantique est estimée à partir des mesures de transports solides à 200 t.km-2. an-1 en moyenne. Ce flux correspond à 69 % du flux théorique de particules potentiellement érodées sur le bassin versant. Les 31 % qui restent peuvent être attribués à l’alluvionnement dans la plaine.
La comparaison des transports solides fluviaux au cours des différentes cures d’une même année met en évidence l’importance des processus hydrologiques dans le contrôle des phénomènes d’érosion mécanique. De même, une étude menée sur trois années hydrologiques différentes (sèche, moyenne et humide) permet de suivre l’évolution de la géodynamique actuelle dans ce bassin à l’échelle interannuelle. Les résultats ainsi obtenus permettent d’établir le bilan de l’érosion mécanique aux échelles saisonnière annuelle et interannuelle. Ce bilan traduit en premier lieu le contrôle du climat et par conséquent de l’hydrologie sur la quantité des apports : topographie et la lithologie interviennent en synergie dès lors que les formations les plus facilement érodables se situent en zone de montagne.
Replacé dans le contexte maghrébin, le Tensift montre en moyenne des résultats qui semblent en accord avec ceux obtenus par d’autres auteurs (SNOUSSI et al. 1989, 1990 ; PROBST et AMIOTTE SUCHET, 1992) pour des oueds marocains, algériens et tunisiens. Par contre dans le contexte africain, les tonnages spécifiques du Tensift sont nettement supérieurs (1 à 2 ordres de grandeur) à ceux observés en Afrique tropicale
Surfaces with non-isolated singularities
No full textNeste trabalho, estudamos famílias de curvas genericamente reduzidas. Estendemos para o caso genericamente reduzido alguns resultados conhecidos para famílias de curvas reduzidas como a equivalência entre a Whitney equisingularidade e a resolução simultânea forte da família e a equivalência entre a Whitney equisingularidade e a constância do número de Milnor e da multiplicidade de cada curva Xt da família. Estudamos também a equisingularidade topológica e a Whitney equisingularidade de famílias de superfícies em C3 parametrizadas por germes de aplicações A-finitamente determinados. Em ([51]), Ruas apresentou uma conjectura cujo enunciado diz que se f : (C2, 0) r→ (C3, 0) é um germe de aplicação finitamente determinado, então um desdobramento F a 1-parâmetro de f é topologicamente trivial se, e somente se F é Whitney equisingular se, e somente se o número de Milnor μ(D(ft)) de D(ft) é constante, onde D(ft) é a curva de pontos duplos de ft. Apresentamos contra-exemplos que mostram como esta conjectura pode falhar. Mostramos também uma classe de famílias de germes aplicações ft : (C2, 0) → (C3, 0) em que a conjectura é verdadeira. No caso em que f é homogênea e de coposto 1, mostramos também algumas fórmulas para a multiplicidade da imagem da curva de pontos duplos f(D(f)), o número de Milnor da seção transversal μ1(f(C2)) e o invariante J(f) em termos dos graus de f. Em [44], Nuño-Ballesteros e Jorge Pérez apresentam alguns resultados sobre germes de aplicações f : (Cn, 0) → (C2n-1, 0) com n ≥ 3. Quando f é finitamente determinado, a curva dos pontos duplos D(f) de f tem uma estrutura de curva genericamente reduzida. Apresentamos uma outra forma de abordar alguns problemas descritos em [44] usando resultados sobre curvas genericamente reduzidas.In this work, we study families of generically reduced curves. We extend to the generically reduced case some results known for families of reduced curves as the equivalence between Whitney equisingularity and strong simultaneous resolution of the family and the equivalence between Whitney equisingularity and the constancy of the Milnor number and the multiplicity of each curve Xt of the family. We also study the topological triviality and the Whitney equisingularity of families of surfaces in C3 parametrized by A-finitely determined map germs. In [51], Ruas presented a conjecture whose statement says that if f : (C2, 0) → (C3, 0) is a finitely determined map germ, then an 1-parameter unfolding F = (ft, t) of f is topological trivial if and only if it is Whitney equisingular if and only if the Milnor number μ(D(ft)) is constant, where D(ft) is the double point curve of ft. We present counter-examples that show how the conjecture can fail. We also show a class of families of map germs ft : (C2, 0) → (C3, 0) in which the conjecture is true. We also give formulas for the multiplicity of the image of the double point curve f(D(f)), the Milnor number of the transversal generic section μ 1f(C2)) and the invariant J(f) in terms of degrees of f in the case in which f is homogeneous and has corank 1. In [44], Nuño-Ballesteros and Jorge Pérez give some results in the case of families of map germs f : (Cn, 0) → (C2n-1, 0) with n ≥ 3. When f is finitely determined, the double point. curve D(f) of f is a generically reduced curve. We present another way of approaching some problems in [44] using results on generically reduced curves
Generic sections of essentially isolated determinantal singularities
No full textInternational audienceWe study the essentially isolated determinantal singularities (EIDS), defined by Ebeling and Gusein-Zade [S. M. Gusein-Zade and W. Ebeling, On the indices of 1-forms on determinantal singularities, Tr. Mat. Inst. Steklova 267 (2009) 119-131], as a generalization of isolated singularity. We prove in dimension 3, a minimality theorem for the Milnor number of a generic hyperplane section of an EIDS, generalizing the previous results by Snoussi in dimension 2. We define strongly generic hyperplane sections of an EIDS and show that they are still EIDS. Using strongly general hyperplanes, we extend a result of Le concerning the constancy of the Milnor number
Modalités de transfert des métaux à l'interface continent-océan - quelques exemples
No full textL'établissement des bilans géochimiques en zone
côtière au débouché des rivières est très difficile à réaliser ; il nécessite en effet la prise en compte de plusieurs processus, notamment la quantification des apports fluviatiles, le rôle joué par les estuaires en tant que pièges, filtres ou mobilisateurs des éléments métalliques, enfin les quantités évacuées en mer.
A travers l'étude de 3 rivières (Adour, Sebou et Souss), il est
apparu que ce sont principalement les facteurs hydrodynamiques qui contrôlent la distribution et le transfert des métaux Pb, Zn, Cu, Ni Cr et Rb depuis les sources géologiques jusqu'aux dépôts marins. Secondairement, le climat, par l'intermédiaire de la plus ou moins grande abondance de la végétation, donc de la matière organique, oriente préférentiellement la phase organique ou minérale pour le transport de ces métaux.
Dans le milieu estuarien, les processus sont plus complexes. D'après les résultats préliminaires obtenus sur quelques estuaires marocains, il semblerait qu'ils se comportent comme une voie de transit en période de forts débits alors qu'ils jouent un rôle mobilisateur en période d'étiage
Status of Euro-Mediterranean coastal marine habitats: loss and trends
No full textWe have reviewed estimates of large-scale trends in the distributions and status of Euro-Mediterranean coastal habitats. Conspicuous declines of coastal wetlands, seagrasses, biogenic reefs, and complex macroalgae have been observed in several countries. In some regions, most valuable habitats were already severely degraded or driven to virtual extinction well before 1900. Nowadays less than 15% of the coastline is considered in "good" condition. Those fragments of native habitats that remain are under threat, and their management is not informed by adequate knowledge of their distribution and status
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