Application of X-Band Wave Radar for Coastal Dynamic Analysis: Case Test of Bagnara Calabra (South Tyrrhenian Sea, Italy)

Sea state knowledge has a key role in evaluation of coastal erosion, the assessment of vulnerability and potential in coastal zone utilization, and development of numerical models to predict its evolution. X-band radar measurements were conducted to observe the spatial and temporal variation of the sea-state parameters along a 3 km long sandy-gravelly pocket beaches forming a littoral cell on Bagnara Calabra. We produced a sequence of 1000 images of the sea state extending offshore up to 1 mile. The survey has allowed monitoring the coastline, the directional wave spectra, the sea surface current fields, and the significant wave heights and detecting strong rip currents which cause scours around the open inlets and affect the stability of the submerged reef-type breakwaters. The possibility to validate the data acquired with other datasets (e.g., LaMMA Consortium) demonstrates the potential of the X-band radar technology as a monitoring tool to advance the understanding of the linkages between sea conditions, nearshore sediment dynamics, and coastal change. This work proves the possibility to obtain relevant information (e.g., wave number, period, and direction) for evaluation of local erosion phenomena and of morphological changes in the nearshore and surf zone

DETERMINISTIC SEA WAVE AND SHIP MOTION FORECASTING: FROM REMOTE WAVE SENSING TO PREDICTION ERROR ASSESSMENT

Presently, the assessment of the operational safety of ships and offshore structures is typically addressed within a statistical framework, both at design stage and for the specification of operational limits. Recently, however, the availability of new remote sensing technologies is paving the way for complementary approaches based on deterministic predictions of sea waves and ship motions. In this respect, the marine wave radar is considered as the key asset for the deterministic prediction of wave elevation. Indeed, the possibility of measuring the sea surface, almost instantaneously and for large areas, can be used to forecast the wave elevation at the location of the operating units. Eventually, the coupling of deterministic wave forecast with suitable ship motion models opens the possibility for giving anticipated prediction and guidance. The application of this emerging approach can be beneficial to those short-time offshore operations requiring sea wave or ship motions to be forecast in the time horizon of tens of seconds to minutes. This envisages the possibility of development of finely tuned early warning, hazard control and support decision systems. One of the main aspects of this chain of models, which is oftentimes overlooked, is the importance of providing the forecast with a consistent assessment of the prediction error. Moreover, the additional sources of uncertainty coming from the wave measurement and from the inversion of the wave radar images are also seldom accounted for. In this thesis, the whole chain of models, that from the wave radar measurement leads to the ship motion prediction, is investigated. The first step is the proposal of a novel technique for the inversion of wave radar images that can consistently account for those regions of the sea surface that cannot be uniformly illuminated because of the shadowing effect. The adoption of a linear least square fitting approach, provided with a regularization technique, allows the proposed inversion method the needed flexibility to address the shadowed regions as missing data. Afterwards, the assessment of the error associated with deterministic wave predictions is addressed. A novel semi-analytical procedure is proposed which allows estimating the ensemble variance of prediction error, in a simple and flexible way, naturally embedding the characteristics of the linear fitting and propagation procedures. The approach also allows the inclusion, in the estimation of prediction error, of the effect of measurement error coming from the radar inversion techniques. The same technique for the estimation of wave elevation prediction error is then extended to linear ship motions, using linear transfer functions. In fact, the developed framework can deal with any linear transformation of the wave elevation, resulting in the definition of a sound measure of the prediction error of linear responses. The method can be used to provide deterministic predictions with confidence intervals, as well as for a consistent setup of the whole forecasting chain. The developed models are then tested for a set of application examples considering both linear and nonlinear wave fields. In this latter respect, a high order spectral method has been implemented to provide more realistic wave elevation fields. Example applications regarding linear ship motions have also been carried out. The proposed inversion procedure has shown interesting results for synthetic radar images generated from both linear and moderately nonlinear wave fields. However, further investigations are needed to reduce the high computational cost required for the inversion. The proposed approach for wave and ship motion prediction error, instead, can represent a convenient novel sound method for the consistent setup of deterministic prediction procedures, remaining, however, limited to those scenarios where nonlinearities play a minor role

Seventh International Symposium "Monitoring of Mediterranean Coastal Areas. Problems and Measurement Techniques"

The Seventh International Symposium Monitoring of Mediterranean Coastal Areas. Problems and Measurement Techniques (Livorno, Italy June 19-20-21, 2018) was organized by the CNR-IBIMET in collaboration with the City of Livorno, the LEM Foundation, the FCS Foundation and the Compagnia dei Portuali di Livorno, with the patronage by Accademia Nazionale dei Lincei, Accademia dei Georgofili, The University of Florence, the Tuscany Region and the North Tyrrhenian Sea Port System Authority. The Symposium, in which scholars from all over the Mediterranean basin participated, was an opportunity to illustrate new proposals and to promote actions to protect the Mediterranean coastal marine environment. In particular, the event was characterized by the search for technical and instrumental solutions to problems related to: energy production in the coastal area, morphology and evolution of coastlines, flora and fauna of the littoral system, management and integrated coastal protection, coastline geography, human influence on coastal landscape