River-coastal-ocean continuum modelling and assessment of nearshore dynamics

Complex processes involved in the river delta areas are not fully solved with a traditional structured-mesh model. A seamless unstructured-grid approach could serve as support to advance in the reproduction and understanding of the dynamics processes across different scales. In this work, a river-coastal-ocean continuum modeling representation has been developed for the Tiber River delta, including the surrounding coastaland open-ocean zones of the Lazio coast (Tyrrhenian Sea, Italy). This area has been selected because it includes important naturalistic sites but also a new commercial, fishery and leisure harbor whose the realization is scheduled for 2023. By using temperature and salinity profiles from near-river CTD data, we demonstrate that this representation simulates the coastal dynamic processes in the Tiber delta zone better than the classic coastal-ocean representation, minimizing calibration and sensitivity experiments. In this work, a large effort has been dedicated to the acquisition of new observations (CTD, drifters, currents radar, bathymetric survey) carried out over different spatial (open-ocean, coastal and near- and along-river) and temporal scales. Validation demonstrated that the model has good accuracy, also in reproducing the salt wedge intrusion along river. Furthermore, currents investigation suggested the existence of an anticyclonic gyre in proximity of the river mouth of the northern branch, mainly induced by river discharge and coastal morphology. These promising results in simulating cross-scale processes in a seamless fashion, will be included in the near future in an operational system for coastal forecasting.