Numerical wave models are critical in hindcasting reliable long-term time series of significant wave heights, which play a crucial role in coastal and ocean engineering activities. Although wind fields are an important input to numerical wave models, few studies have investigated the feasibility of the widely used ERA5 wind reanalysis dataset in fetch-limited basins. In this work, we investigated the feasibility of the ERA5 forced numerical wave model (SWAN) in fetch-limited basins. ERA5 wind velocities were first compared to ground-based meteorological stations, showing poorer accuracy compared to finer gridded ALADIN wind data. Subsequently, the white-capping coefficient C_ds in the Janssen white-capping formulation was calibrated separately using a surrogate model when establishing the ERA5 and ALADIN forced wave models. The calibrated ERA5 forced model showed a similar agreement to wave buoy data as the calibrated ALADIN forced wave model during the calibration period and even superior accuracy in the validation period. Overall, these results show that the wave model calibration procedure mitigates the effect of the poorer accuracy of the ERA5 wind data on the significant wave height results. Nevertheless, both ERA5 and ALADIN forced wave models showed an alarming overprediction for high simulated significant wave heights.

The volume of material required for the construction of new and expansion of existing beach sites is an important parameter for coastal management. This information may play a crucial role when deciding which beach sites to develop. This work examines whether artificial neural networks (ANNs) can predict the spatial variability of nourishment requirements on the Croatian coast. We use survey data of the nourishment volume requirements and gravel diameter from 2016 to 2020, fetch length, beach area and orientation derived from national maps which vary from location to location due to a complex coastal configuration on the East Adriatic coast, and wind, tide, and rainfall data from nearby meteorological/oceanographic stations to train and test ANNs. The results reported here confirm that an ANN can adequately predict the spatial variability of observed nourishment volumes (R and MSE for the test set equal 0.87 and 2.24 × 10⁴, respectively). The contributions of different parameters to the ANN’s predictive ability were examined. Apart from the most obvious parameters like the beach length and the beach areas, the fetch length proved to be the most important input contribution to ANN’s predictive ability, followed by the beach orientation. Fetch length and beach orientation are parameters governing the wind wave height and direction and hence are proxies for forcing.

An understanding of the relationship between the flow generators and harbor design could result in an acceptable seawater renewal into an enclosed basin. The flushing culverts located in the breakwater are the most cost-effective technique for improving water renewal in port engineering. The aim of the paper was to identify and quantify the relation between flow generators and culvert flow to propose an optimal position for the flushing culverts. Mentioned relations are important for designing and positioning the flushing culverts in marinas to achieve optimal sea exchange in the marina basin. Field measurements in the marina Opatija were performed and the data served for calibrating a 3D circulation model and a wave generation/propagation model. The absolute volume of the flow through the culverts caused by wind waves has the more important contribution to the water renewal in the marina basin than the coastal springs have. The optimal flow rates through the culverts are performed by positioning the flushing culvert axis at the mean sea level in accordance with the main incident direction of the propagating waves.

An important aspect that must be considered in harbor design and construction is the water quality within the basin, which depends on the water exchange between the harbor and surrounding water body. Of the most internationally distinguished methods for this purpose (mechanical shakers, overflows, pumps, permeable breakwaters), the most cost-effective method is to use flushing culverts through the body of the breakwater structure. This paper presents physical model results of a flushing culvert functioning with variations of the flushing culvert diameter (D), length (L_c), and vertical position in relation to the water surface level (W). A physical model (rubble mound breakwater) was placed in the wave channel with a piston-type wave generator, where spectral waves were generated. During the measurements, three different hydraulic processes of the wave transmission were observed, depending on the position of the water surface. The research results are presented as transmission coefficients (K_t).