**9. Concluding Remarks**

This paper deals with the mathematical modeling needed to assess the physical effects induced by sediment handling operations in marine and coastal areas. In particular, it aims at:


The proposed integrated modeling approach for simulating sediment dispersion is intended as a flexible framework to estimate sediment dispersion due to marine sediment handling operations. It has been developed to assess the spatial and temporal variability of suspended sediment concentration and deposition rate by means of hydrodynamic, sediment source and transport models implementation. Different levels of accuracy are suggested for different project and operational phases based on the presence of environmentally sensitive critical issues (if any) and the classification of specific environmental contexts: coastal areas, semi-enclosed basins and offshore areas. In particular, paying attention to the feasibility of the modeling studies, it is proposed to perform a series of analyses with increasing details. Then, detailed (and computational onerous) simulations are suggested only if critical issues are likely to arise based on preliminary information and modeling phases. In order to guide the readers in all the steps of the proposed methodology, a further paper dealing with a series of case studies is in preparation.

One of the main uncertainties in the proposed integrated modeling approach implementation is related to the sediment source estimation. Indeed, site-specific data are required to obtain accurate estimate for release/sedimentation fluxes related to excavation, loads and dumping phases. Here the combined use of in situ data and numerical results is claimed to be powerful. Whereas the numerical results represent the variability of suspended sediment concentration at different time-scale far from the intervention site with acceptable reliability, in situ data are needed to gain insight on detailed aspects of the processes that influence its variability along the horizontal and vertical directions. Specific measurement and monitoring campaigns are among the challenges for giving more accurate model results. Then, the modeling–monitoring feedback system is proposed to be well suited as a framework to support the modeling practice, both with respect to the model and the data requirements. As part of the proposed modeling approach, it contributes to an integrated and application-oriented use of models and observations to monitor physical processes in different project phases (also in operational setting). Moreover, within a modeling–monitoring feedback system, the implementation of an environmental information managemen<sup>t</sup> system and the compilation of project data sheets are promoted for a better application of the proposed integrated approach approach (before, during and after each design and monitoring phases). In particular, project data sheets compilation is encouraged to constantly enrich the available dataset and to maximize the usefulness of field data acquired during the various design phases of the project to be monitored and to support the initial phases of future projects characterized by similar environmental and operating conditions.

**Author Contributions:** Conceptualization, I.L., A.F., A.B., A.P., D.P. and M.D.R.; Data curation, I.L., A.F., A.B., A.P., D.P. and M.D.R.; Formal analysis, I.L., A.F., A.B., A.P., D.P. and M.D.R.; Investigation, I.L., A.F., A.B., A.P., D.P. and M.D.R.; Methodology, I.L., A.F., A.B., A.P., D.P. and M.D.R.; Software, I.L., A.F., A.B., A.P., D.P. and M.D.R.; Supervision, I.L.; Validation, I.L., A.F., A.B., A.P., D.P. and M.D.R.; Visualization, I.L., A.F., A.B., A.P., D.P. and M.D.R.; Writing—original draft, I.L., A.F., A.B., A.P., D.P. and M.D.R.; Writing—review & editing, I.L., A.F., A.B., A.P., D.P. and M.D.R.

**Funding:** This research received no external funding. **Acknowledgments:** Massimo Gabellini is kindly acknowledged for his encouraging and precious suggestions. The authors wish to thank also Eng. Maurizio Ferla for his useful suggestions and for promoting the dissemination of the Italian Guidelines.

**Conflicts of Interest:** The authors declare no conflict of interest.
