The Bevano river flows into the northern Adriatic Sea in a microtidal-low energy wave environment. The river mouth was diverted artificially in 2006 to contrast dune erosion and decrease inland river flooding. The intervention can be considered as a low impact one as the engineering works were constructed in timber and the possibility of the inlet naturally changing its course was contemplated. An ensemble of hydraulic/morphological scenarios was simulated using data from field surveys and a coupled numerical model. The aim of the modeling was to understand the morphological changes caused by extreme hydro-meteorological events and the relationships between the inlet and the adjacent beaches. Additionally, the probability of a second inlet opening either by overwashing or river breaching was another important topic considered for management purposes. The modeling found that, a second inlet can actually be opened under a 30 year flood occurring without any significant wave action. For other conditions, the current inlet will be the main source of water escape at sea. Finally, the modeling results confirmed the dominance of the ebb tide in creating a small ebb delta/swash bar, with many similarities with other inlets exposed to a larger tidal range. Currently the management strategy by competent authorities is a minimum maintenance option, with yearly repairs of the timber structures.

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<p>Urban settlements near to coastal environments are exposed to ocean and cryosphere change, such as sea level rise and extreme sea levels. High-resolution sea level prediction systems have become fundamental tools for taking preventive measures in the face of extreme events, mainly in the most vulnerable coastal locations. Techniques such as Machine Learning (ML) are at the forefront of the development in this sector, as they can reduce the computational time needed to reproduce the results of costly high resolution dynamic models. In this line, different authors have reported results for the prediction of oceanographic variables using ML approaches (Camus et al., 2019; Costa et al., 2020; Zust et al., 2021), mainly for significant wave height, sea level and surge component of sea level. Generally, these works use global and/or regional databases as training data for ML tools.</p> <p>With the aim of developing a data-driven system for sea level downscaling, by means of very high-resolution circulation model output used as a training data for a ML framework, in this work the results of a long-term numerical modeling of sea level are presented, carried out in the Northern Adriatic. The numerical model implemented correspond to SURF-SHYFEM, a 3-D finite element hydrodynamic model that solves the primitive equations under hydrostatic and Boussinesq approximations. As atmospheric forcing, mean sea level pressure, and meridional and zonal components of wind speed have been included, both from the ERA5 database. For the boundary conditions, sea level has been considered from two databases, the Copernicus Mediterranean Forecasting System (available from November 2020 to present, with tides included in sea level) and the Copernicus Mediterranean Sea Physics Reanalysis (available from 1987 to June 2021, without tides in sea level). Both databases were used on initial analysis in the representation of surge component of sea level when tides are or not included in the boundary condition. The validation of the results has been carried out by comparison with tide gauges located near the Venice Lagoon, from ISPRA[1] and PSMSL[2].</p> <p>The results show that the model reproduces accurately the sea level (correlation 94% and RMSE 0.09 [m]) and the surge component of sea level (correlation 91% and RMSE 0.06 [m]) measured at the location of the tide gauge. The next step will consist of using such output as a training set for ML-based techniques, with the aim of developing an accurate and cost-effective downscaling tool.</p> <div><br /> <div> <p>[1] Istituto Superiore per la Protezione e la Ricerca Ambientale. Available at: https://www.mareografico.it/</p> </div> <div> <p>[2] Permanent Service for Mean Sea Level. Available at: https://psmsl.org/</p> <p> </p> <p><strong> REFERENCES</strong></p> <p>Camus, P., Herrera, S., Guitiérrez, J.M. and Losada, I.J. (2019). Statistical downscaling of seasonal wave forecast. Ocean Modelling 138, 1-12.</p> <p>Costa, W., Idier, D., Rohmer, J., Menendez, M. and Camus, P. (2020). Statistical prediction of extreme storm surges based on a fully supervised weather-type downscaling model. J. Mar. Sci. Eng. 8, 1028.</p> <p>Zust, L., Fettich, A., Kristan, M. and Licer, M. (2021). HIDRA 1.0: Deep-Learning-Based ensemble sea level forecasting in the Northern Adriatic. Geosci. Model. Dev. 14, 2057-2074.</p> </div> </div>

Abstract:Erosion is striking hard almost all sandy beaches in the Northern Adriatic Sea; among these beaches, the Bibione littoral plays a very important role because of its environmental and socio-economical potential. More of 6 million tourists spend their holidays in Bibione and large parts of the littoral are included in Natura 2000 sites. It is therefore evident that coastal protection cannot be managed using temporary or local solutions, but requires a comprehensive strategy to provide effective solutions in the medium term and full respect of the environment. With a maximum shoreline retreat rate of 10 m/y, the beach can be classified in a very critical condition; despite this, the net sediment balance in the nearshore (i.e. emerged and submerged beach) is close to equilibrium (FONTOLAN, 2014). The sediment management option has been therefore considered as a viable solution for coastal protection; this solution also allows for the minimization of the environmental impact and the preservation of the environmental and touristic value of the area. On this basis, a soft solution has been developed, consisting in the periodic beach nourishment via a stable pipeline which brings the sand dredged at the Tagliamento river mouth to the most critical areas downstream. An extensive monitoring program has been also undergone, together with the design of the pipeline, in order to find all available nearshore deposits and to determine the erosion trend for managing beach nourishment in the next future. The procedure for approval and permitting of the works has been itself a "new design", being the specific regulation the result of a thoroughly debate between scientists, stakeholders and local administrations. Moreover, financing of design and works is a public/private joint venture, most likely the first in Italy. The paper presents all the surveys, investigations and design activities performed in the framework of the Bibione littoral coastal protection plan.