Erosion von Salzmarschrändern durch winderzeugte Wellen

Salt marsh edge erosion due to wind-waves is one of the chief mechanisms leading to marsh area reduction in various parts of the world. This entails the loss of a large amount of ecosystem services in estuarine and coastal environments. The present research seeks to improve the knowledge on the erosion of the boundaries of the salt marshes, focusing on the spatial scale of the salt marsh bank and the adjacent mudflat. The topic is addressed through three different approaches. The interpretation of laboratory experiments, previously carried out, inspired the development of a mathematical model describing the incipient mass failure of toppling type. The model is able to identify the wave group responsible for the failure of a block of soil identified by the presence of a tension crack and gives information about the combinations of water level and wave height leading to bank instability. A field campaign was carried out on a salt marsh of the lagoon of Venice. Localized and detailed measurements of erosion and wave climate allowed to determine a relationship between wave power and erosion rate at monthly time scale. Field data also demonstrated that in the monitored area the lower part of the bank is more prone to erosion than the top, leading to the formation of cantilever profiles. A simple mathematical model based on field data shows that the different erodibility of the marsh scarp along the vertical profile can lead to a higher cumulative retreat of the marsh edge. The development of a 1-D process-based model allowed to investigate, through numerical experiments, the effect of variations of soil composition on the evolution of the bank profile, with and without vegetation. A muddy bank tends to retreat by maintaining the steep profile of the cliff, whereas decreasing the mud fraction the bank attains a more gentle profile. The effect of vegetation in strengthening the soil matrix against shear erosion is negligible for muddy banks and significant for sandy banks. Independently of soil composition, vegetation makes the bank to retreat maintaining a steep profile. Present research gives several insights into the process of erosion of salt marsh edges due to the effect of wind-induced waves. Obtained results can be employed to evaluate and plan measures aimed at the preservation of salt marsh area and they also lay the base for future researches in the field of the morphodynamic evolution of tidal environments.Erosion von Salzmarschrändern durch winderzeugte Wellen ist einer der wichtigsten Mechanismen zur führenden Sumpfgebiet Reduktion in verschiedenen Teilen der Welt. Dies bringt den Verlust einer großen Menge von Ökosystemleistungen in Mündungs- und Küstengebiete. Die vorliegende Untersuchung soll das Wissen über die Erosion der Grenzen der Salzwiesen, die sich auf die räumlichen Skala der Salzsumpf Bank und dem benachbarten mudflat zu verbessern. Das Thema wird durch drei verschiedene Ansätze gerichtet. Die Interpretation von Laborexperimenten, inspiriert vorher durchgeführt, um die Entwicklung eines mathematischen Modells der Beschreibung der einsetzenden Massenausfall des Typs Umkippen. Das Modell ist in der Lage, die Wellengruppe verantwortlich für das Scheitern eines Blocks des Bodens durch das Vorhandensein eines Spannungsriss zu identifizieren und gibt Auskunft über die Kombinationen von Wasserstand und Wellenhöhe zu Bank Instabilität führt. Ein Feld Kampagne wurde auf einem Salz-Sumpf der Lagune von Venedig durchgeführt. Lokalisierte und detaillierte Messungen von Erosion und Wellenklima erlaubt eine Beziehung zwischen Wellenkraft und Erosionsrate in monatlichen Zeitskala zu bestimmen. Felddaten zeigten auch, daß in dem überwachten Bereich der untere Teil der Bank ist anfälliger für Erosion als die Spitze, was zur Bildung von Auslegerprofilen. Ein einfaches mathematisches Modell basierend auf Felddaten zeigt, dass die verschiedenen erodibility des Sumpfes Böschung entlang der vertikalen Profil auf eine höhere kumulative Rückzug des Sumpfes Kante führen kann. Die Entwicklung eines 1-D-Verfahren basierendes Modell erlaubt, durch numerische Experimente zu untersuchen, um die Wirkung von Variationen der Zusammensetzung des Bodens auf die Entwicklung des Bankprofil, mit und ohne Vegetation. Ein schlammiger Bank neigt dazu, durch die Aufrechterhaltung der steilen Profil der Klippe zum Rückzug, während die Verringerung der Schlammfraktion die Bank eine sanftere Profil erreicht. Die Wirkung der Vegetation in der Bodenmatrix gegen Scher Erosion Stärkung vernachlässigbar für schlammige Banken und bedeutsam für Sandbanken. Unabhängig von der Bodenbeschaffenheit, Vegetation macht die Bank zum Rückzug einen steilen Profil. Derzeitige Forschung gibt mehrere Einblicke in den Prozess der Erosion der Salzsumpf aufgrund der Wirkung von Wind-induzierten Wellen Kanten. Die erhaltenen Ergebnisse können bei der Erhaltung der Salzwiesenfläche zu bewerten und zu planen Maßnahmen zur eingesetzt werden, und sie legen auch die Basis für zukünftige Forschungen auf dem Gebiet der morphodynamische Entwicklung von Gezeiten Umgebungen

Mapping human impacts to support sustainable uses of marine ecosystems in the Mediterranean sea

European Geosciences Union (EGU) General Assembly, 23-27 May 2022, Vienna, AustriaLocal and global anthropogenic pressures due to climate change and to local uses and activities are exerting significant cumulative impacts to greater extents of the oceans and seas. Coastal ecosystems are particularly threatened by the intensity and coexistence of several marine uses and pressures, including sewage and urban constructions, tourism, ship traffic, fisheries and aquaculture. Assessment of pressures and the identification of mitigation measures are key urgent actions, as already highlighted by the EU Marine Strategy Framework Directive and the United Nations Sustainable Development Goal 14. The aim of this work, developed within the Interreg-Med project SHAREMED, is to systematize existing knowledge on threats and pollution, including those of transboundary origin, for long term strategies and common action marine spatial planning, jointly developed with stakeholders. The quest is to assess coexisting environmental threats, and their propagation in space and time, at proper spatial and temporal scales, according to the type and action of each stressor (i.e. global vs. local). Cumulative pressures are tackled within a dedicated Atlas comprising three sub-basinsins of the Mediterranean Sea: the North Adriatic Sea, the Sicilian Channel and the North-Western region. The Atlas integrates information generated at the best available resolutions by 1) in-situ sampling, 2) remote observations, 3) numerical models, and 4) focusing on target ecosystems and habitat forming species. These sub-basins are subjected to multiple local and larger scale (e.g. climate) pressures that propagate in space and time, and across political boundaries, that need to be addressed through coordinated actions, based on evidence-rooted common understanding. Interactions with relevant Stakeholders, solicited through an online survey, and meetings, were used to select target ecosystems and to identify the key relevant pressures. The Atlas is based on open-access databases and portals, literature reviews and from ad-hoc model simulations concerning marine heatwaves, ship traffic, oil pollution, marine litter and fishing efforts. We will present the main preliminary results and needs and gaps in observations related to marine ecosystems threatsPeer reviewe

Coastal high-frequency radars in the Mediterranean ??? Part 2: Applications in support of science priorities and societal needs

International audienceThe Mediterranean Sea is a prominent climate-change hot spot, with many socioeconomically vital coastal areas being the most vulnerable targets for maritime safety, diverse met-ocean hazards and marine pollution. Providing an unprecedented spatial and temporal resolution at wide coastal areas, high-frequency radars (HFRs) have been steadily gaining recognition as an effective land-based remote sensing technology for continuous monitoring of the surface circulation, increasingly waves and occasionally winds. HFR measurements have boosted the thorough scientific knowledge of coastal processes, also fostering a broad range of applications, which has promoted their integration in coastal ocean observing systems worldwide, with more than half of the European sites located in the Mediterranean coastal areas. In this work, we present a review of existing HFR data multidisciplinary science-based applications in the Mediterranean Sea, primarily focused on meeting end-user and science-driven requirements, addressing regional challenges in three main topics: (i) maritime safety, (ii) extreme hazards and (iii) environmental transport process. Additionally, the HFR observing and monitoring regional capabilities in the Mediterranean coastal areas required to underpin the underlying science and the further development of applications are also analyzed. The outcome of this assessment has allowed us to provide a set of recommendations for future improvement prospects to maximize the contribution to extending science-based HFR products into societally relevant downstream services to support blue growth in the Mediterranean coastal areas, helping to meet the UN's Decade of Ocean Science for Sustainable Development and the EU's Green Deal goals

Coastal high-frequency radars in the Mediterranean ??? Part 1: Status of operations and a framework for future development

Due to the semi-enclosed nature of the Mediterranean Sea, natural disasters and anthropogenic activities impose stronger pressures on its coastal ecosystems than in any other sea of the world.With the aim of responding adequately to science priorities and societal challenges, littoral waters must be effectively monitored with high-frequency radar (HFR) systems. This land-based remote sensing technology can provide, in near-real time, fine-resolution maps of the surface circulation over broad coastal areas, along with reliable directional wave and wind information. The main goal of this work is to showcase the current status of the Mediterranean HFR network and the future roadmap for orchestrated actions. Ongoing collaborative efforts and recent progress of this regional alliance are not only described but also connected with other European initiatives and global frameworks, highlighting the advantages of this cost-effective instrument for the multi-parameter monitoring of the sea state. Coordinated endeavors between HFR operators from different multi-disciplinary institutions are mandatory to reach a mature stage at both national and regional levels, striving to do the following: (i) harmonize deployment and maintenance practices; (ii) standardize data, metadata, and quality control procedures; (iii) centralize data management, visualization, and access platforms; and (iv) develop practical applications of societal benefit that can be used for strategic planning and informed decision-making in the Mediterranean marine environment. Such fit-for-purpose applications can serve for search and rescue operations, safe vessel navigation, tracking of marine pollutants, the monitoring of extreme events, the investigation of transport processes, and the connectivity between offshore waters and coastal ecosystems. Finally, future prospects within the Mediterranean framework are discussed along with a wealth of socioeconomic, technical, and scientific challenges to be faced during the implementatio