Chiara Francesca Schiaffino

Towards a predictive model to assess the natural position of the Posidonia oceanica seagrass meadows upper limit

The upper portion of the meadows of the protected Mediterranean seagrass Posidonia oceanica occurs in the region of the seafloor mostly affected by surf-related effects. Evaluation of its status is part of monitoring programs, but proper conclusions are difficult to draw due to the lack of definite reference conditions. Comparing the position of the meadow upper limit with the beach morphodynamics (i.e. the distinctive type of beach produced by topography and wave climate) provided evidence that the natural landwards extension of meadows can be predicted. An innovative model was therefore developed in order to locate the region of the seafloor where the meadow upper limit should lie in natural conditions (i.e. those governed only by hydrodynamics, in absence of significant anthropogenic impact). This predictive model was validated in additional sites, which showed perfect agreement between predictions and observations. This makes the model a valuable tool for coastal management.

Evaluation of the effectiveness of a seasonal nourishment programme of the pocket beaches of the city of Genoa

The aim of the study was to monitor several beaches of the city of Genoa following artificial nourishment programmes carried out in 2003. The programmes, which involved depositing fluvial material from the Bisagno Torrent in the swash zone, were carried out as part of the seasonal nourishment of the beaches of Boccadasse, Bagnara and Caprafico to the east of Genoa, which are subject to intense erosion. The study provided for a preliminary survey in April 2003, before the nourishment, and three other surveys were subsequently carried out to evaluate the effectiveness of the intervention through the evolution of the beach. The morphological and sedimentological surveys were carried out in July and November 2003 and April 2004 to evaluate the development of the beach in both high and low energy situations. The suitability of the material was evaluated using the method proposed by Hobson. From the data obtained from the field studies it was possible to demonstrate that the interventions had only partially counteracted the annual sedimentary losses of the beaches. The quantities of material deposited were inadequate to enable the beaches to re-equilibrate their compromised morphodynamic profiles and adapt to the wind-wave conditions. Therefore, we consider it essential to undertake the reconstruction of the beaches and not simply try to maintain them in this way. The use of greater quantities of material would permit not only the widening of the backshore but also the creation of more stable morphodynamic profiles that would last longer.

Evaluation of a nourishment programme with a webcam: the case of Levanto (La Spezia, Italy)

This paper presents the results of a monitoring programme of the littoral of the town of Levanto (La Spezia) to evaluate the efficiency of a nourishment project carried out on a gravel beach. The study was carried out with a webcam, one of the most innovative techniques for monitoring coastal evolution. This technique makes it possible to automatically obtain a continuous, real-time set of images of high quality that can then be processed with dedicated software to provide information on the morphodynamic conditions of the beach. The image processing technique, [based on the studies carried out by the Coastal Imaging Laboratory of Oregon State University to develop the Argus System], was developed by the Dipartimento per lo Studio del Territorio e delle sue Risorse (Dip.Te.Ris.) and the Dipartimento di Matematica (Di.Ma.) of the University of Genoa. The research was focused on studying the variations in the shoreline following a nourishment programme as revealed by a comparison of the processed images, which made it possible to reconstruct the evolution of the beach in the short- and medium-term and thereby evaluate the efficiency of the intervention.

Storm Hazard Assessment for Urban Areas

Storm surges are one of the most significant threats for coastal urban areas. In view of finding a way to minimize sea storm damages to anthropic structures, this paper focuses on the analysis of storm hazard investigation methods and on coastal control line definition. Generally, coastal control lines are identified through Run up equations proposed by Mase (1989). Applicability of Van der Meer equations (1998), usually employed for beach profile analysis, will be assessed here as an alternative to Mase equations. Three urban beaches on Genoa coast are considered: Voltri beach, Pegli beach and Vernazzola beach. The analysis takes into account sea and weather condition data collected during three major storm surges in the aforementioned littoral areas. Empirical data gathered in field surveys during storms were subsequently examined in order to analyze seaside area response. Collected data were compared with theoretical computations. Results show a greater significance of data obtained through the application of Van De Meer (1998) equation than Mase equation data (1989). In conclusion, Van De Meer (1998) equation could provide information about coastal control lines on urban gravel beaches. Such information would then be useful to locate high hazard areas and act accordingly.

A free software for sand and gravel embayed beach modelling: PhoEbuS- parabolic equation shape

An in-depth knowledge of the littoral system is essential for its conservation and for an accurate planning of due interventions. The parabolic bay shape equation, used to study the embayed beach planform, is a qualitatively assessed instrument to obtain information about beach equilibrium conditions. Nowadays the equation has been extended in order to be applicable not only to sand beaches but also to gravel beaches. In this paper Phoebus user-friendly software for an automatic use of the extended parabolic bay shape equation is presented. The software enables both technical experts and non-professionals to conduct expeditious analysis in order to evaluate the evolution and equilibrium conditions of embayed littoral beaches lying between natural headlands or man-made structures, as well as to artificially recreate stable embayed beaches by building new artificial structures on open beaches. The software can be also used for coastal planning, to anticipate beach modifications in response to new building or to changes in pre-existing structures.Highlights1.Development of a free software to automatically compute embayed beach planform2.The system can be used on every type of beach image3.The software allows to display the planform both for sand and gravel beaches4.Software reliability was demonstrated for natural and artificial bay beaches