Human pressures on the coastal zones and oceans have increased considerably in the last decades. Human activities constitute the greatest threat to the coastal and marine environment, generating considerable quantities of plastic waste. Currently, it is widely recognized that the increase of marine-related activities has adversely affected the coastal environment as well as the associated ecosystems. Our study focuses on marine litter and specifically on the floating part of it which is frequently composed of plastic materials. Floating litter tends to accumulate on beach-dune ecosystems, already characterized by multiple anthropogenic pressures and environmental factors. In addition, litter items may be trapped by coastal dune vegetation or saltmarsh. Successively, the degradation of marine litter will cause the entering of secondary microplastics. Most of the previous studies are based on monitoring activities and aim to identify the origin and destination of litter in order to manage the fate and transport issues. Therefore, it is important to develop modeling and monitoring tools to detect and prevent marine debris dispersal in coastal environments. We applied field sampling and UAVs (Unmanned Aerial Vehicles) survey over a complex geomorphic set up in the Po River Delta (Italy). Our field data are implemented into a high-resolution hydro-morphodynamic numerical model for validation. Then, we are able to project into different scenarios of plastic debris accumulation in the coastal zone. Our preliminary results show an accumulation of floating debris in coastal dunes vegetation mainly driven by alongshore currents and wave set up in the nearshore area. Then, wind-dominated directions and magnitude disperse plastic debris in embryo dunes and back-barrier marshes. Specific cleaning operations are therefore needed. Considering that coastal management scenarios and decisions rely on numerical models that can predict best practices for coastal sustainability, our results might help local agencies and stakeholders to manage coastal environments.

River deltas and enclosed lagoons represent a zone where fluvial and littoral processes interacts through a redistribution, erosion, and deposition of sediment, with a huge impact on coastal management and engineering. The focus of the study is to understand the correct balance between strategies to maintain the navigational efficiency of tidal inlets and the respect of the ecological and economical function in coastal lagoons. We applied an integrated modeling system which will link multiple hydrodynamic and morphodynamic models to understand how coastal processes and the associated sediment transport can influence the functioning of the southern inlet of the Barbamarco lagoon in the Po River Delta, Italy. Furthermore, our study provides engineering solutions aimed at the inlet functioning efficiency with a proposal for the monitoring plan. Our results highlight the importance of the seasonal effects of wave climate on the littoral sediment transport. Model outcomes show that the dredging volume is approximately 15,000 cubic meter/year for the southern inlet that might vary with wave climate. However, shaping a wider tidal channel seaward will reduce the dredging activities with a longer interval than the actual sediment removal. A design of a deeper and wider channel will deflect the along shore current seaward with a sediment bypass of the inlet. Therefore, the sediment will reach the erosional side of the inlet enhancing the redistribution of the sediment which might reduce the over-wash during storms and high-water levels. Our results display the ephemeral equilibrium of tidal inlets and coastal lagoons in deltaic systems impacted by large riverine sediment delivery. Shore management scenario and decision relies on hydro-morphodyanmic numerical model to predict the best practice for coastal sustainability.