Coastal and port engineering

In this paper, we present recent evolvements of three robust numerical models for the simulation of the evolution of wave fields and hydrodynamic circulation in gulfs and coastal areas with large harbours and significant urban port facilities. The models are integrated into a single software suite for the development of a decision support tool to provide reliable forecasts of sea states prevailing at selected important ports worldwide. The application of the integrated modelling platform is designed to support approaching procedures of vessels to ports and it is based on co-operating, high-resolution, hydrodynamic (ocean and wave) models that derive input data and boundary conditions from global scale or regional, open sea and weather forecasts. The implementation of short-term forecasts for sea conditions includes the development, validation, coupling, and operational application of: i) the High Resolution Storm Surge (HiReSS) model for sea level variations; ii) the 3rd generation spectral wave model called TELEMAC-based Operational Model Addressing Wave Action Computation (TOMAWAC) for irregular wave propagation in offshore and coastal areas; and iii) a high resolution phase-resolving wave model (WAVE-L) for port basins, based on the hyperbolic mild-slope equations. This innovative product, designed for port-related endusers, will improve the navigation safety at ports, optimize the berth occupancy, support the port pilotage operations, mooring and towage procedures, and may facilitate the port layout upgrade or design. Hereby, pilot forecast implementations are presented concerning the Mediterranean Sea and eight selected harbours in it.

This paper presents a novel initiative for reliable high-resolution forecasts on prevailing sea states at 50 important ports worldwide (Accu-Waves; http://accuwaves.eu/). Its goal is to support safe navigation, unhampered vessel approaching to busy harbored areas, and secure ship maneuvering in ports. Accu-Waves 1 is based on integrated, high-resolution, ocean and coastal modeling that uses data from global scale, open-sea forecasts as boundary conditions. The models' setup, coupling, nesting, calibration, verification, and application are reported herein, concerning areas near and inside globally significant port basins. Thus, we present the automated operational setup of the Accu-Waves service for three-day forecasts at three-hourly intervals.

In this paper we present the evolvement of an integrated numerical model (WAVE-L) for the simulation of wave propagation and transformation in areas around and inside ports and harbors. WAVE-L is a high-resolution phase-resolving wave model based on the hyperbolic mild-slope equations, capable of simulating the transformation of complex wave fields over varying bathymetries in harbors and coastal areas in the vicinity of ports. The modeled wave processes include shoaling, refraction, diffraction, total and partial reflection from structures, energy dissipation due to wave breaking and bottom friction in a combined way. The new version of WAVE-L incorporates wave generation simulated on any boundary (longitudinal, lateral or oblique) with corresponding expansion of peripheral sponge layers, providing potential to spatially restrict the computational field in areas adjacent to ports, thus reducing demand of computational time and resources. Moreover, the modified WAVE-L version is able to simulate quasi-irregular, multi-directional waves, whose generation and propagation may furthermore account for various angles and directions simultaneously. WAVE-L is one-way coupled to coarser implementations of an open-sea spectral wave model and a 2-DH hydrodynamic circulation model for storm surges that provide input and boundary conditions. WAVE-L model is thoroughly validated against experimental data on diffraction and multidirectional spectral wave propagation; pilot implementations of it are carried out at the Greek port basin of Thessaloniki. The ultimate goal is to create a tool for high-resolution operational forecasts of wave conditions around and inside significant ports with high traffic load and commercial value (project Accu-Waves).

In the present work, a methodological framework, based on nonstationary extreme value analysis of nearshore sea-state parameters, is proposed for the identification of climate change impacts on coastal zone and port defense structures. The applications refer to the estimation of coastal hazards on characteristic Mediterranean microtidal littoral zones and the calculation of failure probabilities of typical rubble mound breakwaters in Greek ports. The proposed methodology hinges on the extraction of extreme wave characteristics and sea levels due to storm events affecting the coast, a nonstationary extreme value analysis of sea-state parameters and coastal responses using moving time windows, a fitting of parametric trends to nonstationary parameter estimates of the extreme value models, and an assessment of nonstationary failure probabilities on engineered port protection. The analysis includes estimation of extreme total water level (TWL) on several Greek coasts to approximate the projected coastal flooding hazard under climate change conditions in the 21st century. The TWL calculation considers the wave characteristics, sea level height due to storm surges, mean sea level (MSL) rise, and astronomical tidal ranges of the study areas. Moreover, the failure probabilities of a typical coastal defense structure are assessed for several failure mechanisms, considering variations in MSL, extreme wave climates, and storm surges in the vicinity of ports, within the framework of reliability analysis based on the nonstationary generalized extreme value (GEV) distribution. The methodology supports the investigation of future safety levels and possible periods of increased vulnerability of the studied structure to different ultimate limit states under extreme marine weather conditions associated with climate change, aiming at the development of appropriate upgrading solutions. The analysis suggests that the assumption of stationarity might underestimate the total failure probability of coastal structures under future extreme marine conditions.

Forecast of wave agitation inside port basins and consequent downtime of berth positions are of utmost importance to make a port "smarter" by efficiently managing its infrastructure. Within Accu-Waves project (http://accuwaves.eu), a decision-making tool is being developed to provide forecast data on prevailing sea states in the vicinity of port entrances and inside harbour basins. The said tool will be based on cooperating hydrodynamic models that derive data from global scale, open sea forecasts. The implementation of the project includes development and application of a hydrodynamic circulation model, a spectral wave propagation model and a phase-resolving wave model for port basins. The latter is based on the hyperbolic mild-slope (HMS) equations, capable of simulating wave propagation and reflection. In order to achieve higher levels of simulation accuracy in the vicinity of waterfront structures, we need to robustly model the reflection of incipient waves from such structures (e.g., quay walls). In the present paper, this need is met through the incorporation of an additional, casespecific eddy viscosity coefficient to the governing mildslope equations (of the phase-resolving wave model). This coefficient accounts for the energy dissipation on port structures' fronts and its value is decided based on the corresponding reflection coefficient. A basic set of incident wave scenarios are simulated, required in investigating the numerics of reflection by the corresponding eddy viscosity coefficients in the wave model. Our pilot investigation refers to numerical experiments for several cases of waves approaching an either fully or partially reflective vertical quay wall. The proposed methodology could enhance similar HMS models; its results should be valuable for port operators.

The ability to reliably forecast sea states (most importantly sea level, wind, and wave conditions) within or close to the entrance of ports is a critical tool for all involved stakeholders. In this paper, we present our work on a prototype decision support system capable of providing accurate sea state forecasts based on three high-resolution hydrodynamic models, i.e. a spectral wave model (model A), a mild-slope equation wave model (model B), and a barotropic hydrodynamic circulation model (model H). We present an end to end novel data processing pipeline, capable of handling the challenges posed by the volume of related data and capable of providing high-resolution wave forecasts by exploiting parallelization.