1,721,115 research outputs found
SWASH BAR BEHAVIOUR ON A PROTECTED MICROTIDAL BEACH: LIDO DI DANTE, ITALY
No full textThe morphodynamics of a microtidal protected beach during
medium-wave energy conditions is examined in this paper. The significant wave attenuation due to the inshore protection structures permits to assess the action of swash processes on swash bar morphodynamics. Under very low energy conditions (Hs < 0.1 m) no significant morphological changes were observed. However, the swash bar situated in the upper part of the intertidal beach migrated landward by ~ 1m/tide during two consecutive tides when the significant wave heights were around 0.4 m. The migration processes ended in the change of the morphology of the swash bar from a low-amplitude bar to a slip-face ridge. A high resolution shallow water model (SWAN) was used with the local wind and wave measurements to produce wave induced force (WIF) vectors predictions over the study area. A significant relationship between the WIF vectors thickness and bed response was found
Degradation of a dune-ridge at a yearly time-scale:impact of human activities and occurrence of storms
No full textMorphodynamics of a microtidal protected beach during low wave-energy conditions
No full textThis paper presents detailed hydrodynamic and morphological data from a field experiment spanning 5 days (10 tidal cycles, starting at Spring Tide conditions) undertaken in Lido di Dante, a microtidal protected beach in the Northern Adriatic Sea. This microtidal beach experienced intense erosion in the recent past and therefore it has been protected by groins, nourishments and a semi-submerged breakwater (Low-Crested Structures). During the fieldwork, an intertidal swash bar formed at spring tide under very low wave-energy conditions. The swash bar migrated 3.5 m landwards during two consecutive tides when the measured maximum significant wave height at the upper beach was around 0.2 m. This migration was associated with an onshore sediment transport, resulting from the erosion of the bar's seaward slope. Once the tidal range decreased during the last tides and wave action ceased, the swash bar became static and only some non-significant changes were observed on both seaside slope and bar slip-face. The net volumetric change of this beach during the fieldwork was non-significant, in spite of the swash bar landward migration (cross-shore redistribution of the initial beach sediment budget). The wave attenuation generated by the beach protection structures was highlighted through comparison between wave measurements inside and Outside the barrier. This had a significant role on swash processes and tide controlled duration of swash action, which controlled the cross-shore bar's morphodynamics in the absence of significant longshore processes
Morphological change by overwash on a microtidal backshore: Bevano beach, Northern Adriatic Sea
No full textInternational audienc
Abstract : Understanding the morpho-sedimentary dynamics of cohesive and non- cohesive beaches in the South-Brittany region (France) at different spatiotemporal scales.
No full textÀ l'échelle du monde, les littoraux peuvent se diviser en différentes catégories : les côtes rocheuses, sableuses, vaseuses et mixtes. Cependant, les littoraux meubles sableux et vaseux sont retrouvés régulièrement mélangés sur différentes façades côtières mondiales. Des apports de vases temporaires ou permanents sont en effet observés sur des plages sableuses. Ces environnements mixtes atypiques, qui couplent alors les processus d’érosions, de transports et de dépôts associés à la fois aux sédiments cohésifs et non cohésifs, ont été peu étudiés. Afin d’identifier les forçages des variations morpho-dynamiques sur des environnements sableux et mixtes, quatre plages sablo-vaseuses ou entièrement sableuses de type Low-Tide-Terrace ont été suivies mensuellement sur deux années en baie et estuaire de la Vilaine (Bretagne Sud). Des suivis hydro-morpho-sédimentaires spécifiques à haute résolution et des suivis par photogrammétrie ont été menés ponctuellement sur ces sites. À l'échelle régionale, ce travail met en évidence le rôle de la morphologie initiale et l’héritage géologique régional dans la réponse morphologique du littoral de la baie de Vilaine aux conditions d’énergie extrêmes. La capacité de résilience à moyen-terme du littoral des plages de Bretagne Sud a été démontrée. Dans une approche plus spécifique, un comportement morphodynamique d'une plage sablo-vaseuse proche de celle d'une plage uniquement sableuse a été observé lors des phases de haute énergie. Les variations d’altitudes du platier vaseux et des modelés sédimentaires en ridges and runnels sont principalement contrôlées par l’énergie des vagues mais également par les propriétés physiques des sédiments et particulièrement celles liées à l'interaction entre le sable provenant de la section réflective et la vase de la section dissipative. La capacité d’érosion du platier vaseux par les vagues est potentiellement diminuée au niveau des interfaces des sédiments cohésifs et non-cohésifs.At the world scale, coastal areas can be divided in several categories: rocky, sandy, muddy and mixed coasts. However, these sedimentary coasts are regularly found mixed. Temporary or permanent mud inputs are observed on the sandy beaches. These atypical mixed environments, coupling erosional, transports and deposits processes associated to cohesive and non-cohesive sediments have been poorly studied. So, understanding theirs morphological and sedimentary dynamics and the identification of regional and local forcings driving them are essential. Four sandy-muddy or fully sandy Low-Tide-Terrace beaches from the bay and estuary of Vilaine (South-Brittany) have been monthly monitored over two years to characterize their morphodynamics beahaviors. Specific monitoring of coupled hydrodynamics and morpho- sedimentary surveys and photogrammetry experiments have been conducted on mixed sandy- muddy or full sandy beaches. At a regional scale, this work highlights the role of the initial morphology and regional geology inheritance on the morphological response of the littoral zones to extreme energy conditions. Despite some erosion patterns in local parts of beaches, particularly close to shore protection structures, the mid-term recovery capacity of the south-Brittany coastal area after extreme wave energy conditions have been proved. In a more specific approach, the works regarding the sandy- muddy beach dynamic show a morphodynamics behaviour close to that of a fully sandy beach during high energy event. The mudflat elevation changes and the dynamic of the ridges and runnels sedimentary patterns are mainly controlled by the incoming waves but also by the own physical properties of the sediment, particularly those induced by the interaction between the sand from the reflective section and the mudflat. A sand deposit between mud layers potentially decreases the wave erosion capacity on the mudflat
Experiencia piloto de aprovechamiento de corrientes mareales en la costa de Huelva (TidUtil)
No full textInternational audienceLa integración de tecnologías de energía renovable con la selección innovadora de sitios es esencial para abordar los desafíos energéticos globales. En este contexto, la propuesta de instalar una turbina de marea en la desembocadura del río Tinto en Huelva ofrece un potencial significativo para futuros estudios e instalaciones similares. Colocar el dispositivo debajo del puente donde se unen los ríos Tinto y Odiel permitirá ensayar distintos métodos de control y contar con un sistema innovador de monitorización y control remoto, convirtiéndose en un referente de la Industria 4.0. La construcción de una planta en la costa de Huelva fortalecerá las infraestructuras de I+D en Andalucí
Experiencia piloto de aprovechamiento de corrientes mareales en la costa de Huelva (TidUtil)
No full textInternational audienceLa integración de tecnologías de energía renovable con la selección innovadora de sitios es esencial para abordar los desafíos energéticos globales. En este contexto, la propuesta de instalar una turbina de marea en la desembocadura del río Tinto en Huelva ofrece un potencial significativo para futuros estudios e instalaciones similares. Colocar el dispositivo debajo del puente donde se unen los ríos Tinto y Odiel permitirá ensayar distintos métodos de control y contar con un sistema innovador de monitorización y control remoto, convirtiéndose en un referente de la Industria 4.0. La construcción de una planta en la costa de Huelva fortalecerá las infraestructuras de I+D en Andalucí
Experiencia piloto de aprovechamiento de corrientes mareales en la costa de Huelva (TidUtil)
No full textInternational audienceLa integración de tecnologías de energía renovable con la selección innovadora de sitios es esencial para abordar los desafíos energéticos globales. En este contexto, la propuesta de instalar una turbina de marea en la desembocadura del río Tinto en Huelva ofrece un potencial significativo para futuros estudios e instalaciones similares. Colocar el dispositivo debajo del puente donde se unen los ríos Tinto y Odiel permitirá ensayar distintos métodos de control y contar con un sistema innovador de monitorización y control remoto, convirtiéndose en un referente de la Industria 4.0. La construcción de una planta en la costa de Huelva fortalecerá las infraestructuras de I+D en Andalucí
A sustainable alternative for coastal dune restoration by sand-trapping fences and algae wrack: AlgoBox ®
No full textInternational audienceShorelines are the locus of significant and diverse economic activity as well as ecosystem services and conservation interest. At a time of global climate change and sea level rise, the type of management being implemented has direct influence on the future of the shoreline and its resources. Several approaches can be taken, but in practical terms, the overwhelming response has been, and continues to be, to armour or nourish the shoreline and prevent it moving. This removes the shoreline's natural resilience, damages the coastal ecosystem and the resources it provides, and has a direct economic cost (in design, construction and maintenance) and indirect costs (through its impact on recreation, scenic quality, tourism potential and several other economic activities). The coast of south Brittany in France is subject to severe erosion. This coast is characterized mainly by seacliffs and headland embayed and pocket beaches with a "low-tide-terrace" active morphology. Wrack deposits (macroalgae: mainly Soleiria Chordalis) also form significant seasonal accumulations on the beaches, thus impacting their morphology and ecosystem. Because of the absence of sediment stocks that could be used for beach nourishment, shoreline management has had recourse, thus far, to "hard" engineering techniques to hold the coastline. The use of "soft" engineering techniques to protect dunes and beaches in south Brittany has been limited to the implementation of sand fences on the dunes to limit human access to these fragile systems. The aeolian sediment transport potential, with a relative abundance of onshore winds on this coast, has unfortunately been under-exploited. In order to gain maximum profit from the aeolian transport potential and from the nutrient release generated by wrack decomposition (which may facilitate plant growth and sediment fixing), we proposed an experimental tool, the "AlgoBox", which consists in sand-trapping fence cases filled by wrack after partial aeolian sand deposition. The fixing of sand in the "AlgoBox" by vegetation colonization is facilitated by the nutrients released by wrack decomposition during spring and summer seasons (Sedrati and Cochet, 2015). This paper presents the design and evaluation of the "AlgoBox" system which has now been successfully experimented at too sites in South Brittany coast (Penvins beach since July 2014 and Kerjouano beach since June 2016) including the regular topographic dune-beach profile surveys, algae wrack decomposition and nutrient generation, vegetation colonization processes and future considerations for the optimal design and improvement of the system as a new tool for ecological engineering of beach-dune systems
A sustainable alternative for coastal dune restoration by sand-trapping fences and algae wrack: AlgoBox ®
No full textInternational audienceShorelines are the locus of significant and diverse economic activity as well as ecosystem services and conservation interest. At a time of global climate change and sea level rise, the type of management being implemented has direct influence on the future of the shoreline and its resources. Several approaches can be taken, but in practical terms, the overwhelming response has been, and continues to be, to armour or nourish the shoreline and prevent it moving. This removes the shoreline's natural resilience, damages the coastal ecosystem and the resources it provides, and has a direct economic cost (in design, construction and maintenance) and indirect costs (through its impact on recreation, scenic quality, tourism potential and several other economic activities). The coast of south Brittany in France is subject to severe erosion. This coast is characterized mainly by seacliffs and headland embayed and pocket beaches with a "low-tide-terrace" active morphology. Wrack deposits (macroalgae: mainly Soleiria Chordalis) also form significant seasonal accumulations on the beaches, thus impacting their morphology and ecosystem. Because of the absence of sediment stocks that could be used for beach nourishment, shoreline management has had recourse, thus far, to "hard" engineering techniques to hold the coastline. The use of "soft" engineering techniques to protect dunes and beaches in south Brittany has been limited to the implementation of sand fences on the dunes to limit human access to these fragile systems. The aeolian sediment transport potential, with a relative abundance of onshore winds on this coast, has unfortunately been under-exploited. In order to gain maximum profit from the aeolian transport potential and from the nutrient release generated by wrack decomposition (which may facilitate plant growth and sediment fixing), we proposed an experimental tool, the "AlgoBox", which consists in sand-trapping fence cases filled by wrack after partial aeolian sand deposition. The fixing of sand in the "AlgoBox" by vegetation colonization is facilitated by the nutrients released by wrack decomposition during spring and summer seasons (Sedrati and Cochet, 2015). This paper presents the design and evaluation of the "AlgoBox" system which has now been successfully experimented at too sites in South Brittany coast (Penvins beach since July 2014 and Kerjouano beach since June 2016) including the regular topographic dune-beach profile surveys, algae wrack decomposition and nutrient generation, vegetation colonization processes and future considerations for the optimal design and improvement of the system as a new tool for ecological engineering of beach-dune systems
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