The flow and sediment transport in the boundary layer at the sea bottom due to the passage of surface waves are determined by considering small values of the wave steepness and of the ratio between the thickness of the boundary layer and the local water depth. Both the velocity field and the sediment transport rate are determined up to the second order of approximation thus evaluating both the steady streaming and the net (wave-averaged) flux of sediment induced by nonlinear effects. The flow regime is assumed to be turbulent and a two-equation turbulence model is used to close the problem. The bed load is evaluated by means of an empirical relationship as function of the bed shear stress. The suspended load is determined by computing the sediment flux, once the sediment concentration is determined by solving an appropriate advection–diffusion equation. The decay of the wave amplitude, which is due to the energy dissipation taking place in the boundary layer, is taken into account. The steady streaming and the sediment transport rate at the bottom of sea waves turn out to be different from those which are observed in a wave tunnel (U-tube), because of the dependence on the streamwise coordinate of the former flow. In particular, in the range of the parameters presently investigated, the sediment transport rate at the bottom of sea waves is found to be always onshore directed while, in a water tunnel (U-tube), the sediment transport rate can be onshore or offshore directed

Abstract:The evaluation of the coastal hazard and vulnerability caused by storm conditions is an important issue related to coastal flooding and erosion. Although these topics have been widely tackled by past research, they cannot be avoided, but need to be carefully managed by local authorities in order to limit damage to coastal infrastructure, to protect human life, habitats and sensitive species. Usually, this issue is tackled through common approaches at the regional scale. This paper illustrates the first steps of a research project aimed at assessing coastal hazard and vulnerability to wave-induced flooding at the national scale. In order to apply the method to the national scale, it is necessary to select a suitable dataset. This has to be consistent with the whole application area, concerning its spatial distribution, reliability and availability. Thus, one of the aims of this project is to perform a comparative analysis using data available at the national and local scale. The analysis was performed for the area of Montalto di Castro (Tyrrhenian Sea) by using datasets with different spatial resolutions. The results revealed that the use of low resolution data does not significantly affect the estimated nearshore wave features, while the wave runup in underestimated by about 25%. This underestimation influences also the vulnerability and hazard assessments. In particular, the vulnerability is conservatively assessed if low resolution data are used. On the other hand, the hazard is conservatively assessed when low resolution data are used only if the wave runup is amplified by considering the 25% underestimation. The results presented herein can be extended to other sites with the same general features (i.e., microtidal and dissipative coastal stretches).

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According to the global growth of the “Blue economy”, coastal zones are under pressure from both land and marine side economic activities. The fragmentation of sectorial interests and legislation along the coasts has led to the need for bridging knowledge (data/information and methods/tools) and governance (decision-makers at every level) in order to ensure sustainable economic development and social and ecosystem resilience. This poses the need for an interaction process that associates user needs to the European and national legislative framework to create a policy-oriented demand of Copernicus Earth Observation services in coastal areas. Such goals need a strong and effective system to monitor compliance and to assess the progress of the legislation. This study aims at identifying potential gaps in the current Copernicus product offer for the monitoring of the coastal sector through the elicitation of stakeholder requirements. The methodology is applied to the Italian landscape of users, but it is scalable at European level. The results provide a clear overview of the coastal user requirements, highlighting the common need of integrated information for the management, and represents the basis for defining the coastal services.

In recent years increasing attention has been paid to environmental effects that may result from marine dredging and disposal operations. In general, the fine-grained fraction of handled sediments can be dispersed far from the intervention site as a turbidity plume, depending on the specific site and operational parameters. Starting from a literature review, this paper suggests standards for estimating and characterizing the sediment source term, for setting up far-field modeling studies and analyzing numerical results, with the aim of optimizing, also from an economic point of view, the different project, execution and monitoring phases. The paper proposes an integrated modeling approach for simulating sediment dispersion due to sediment handling operations in different marine-coastal areas (off-shore, near-shore and semi-enclosed basins). Attention is paid to the characterization of sediment source terms due to different operational phases (removal, transport and disposal). The paper also deals with the definition of accuracy level of modeling activities, with regard to the main physical processes characterizing the different marine–coastal areas and to the type of environmental critical issues near the intervention site (if any). The main relationships between modeling and monitoring are given for the different design and management phases to support the selection of appropriate technical alternatives and monitoring actions and to ensure the environmental compliance of the proposed interventions.