Optimizing dredge-and-dump activities for river navigability using a hydro-morphodynamic model

Worldwide, significant dredging activities of riverbed sediment are employed to ensure that freight transportation on rivers can continue year-round. Imbalances of sediment budget may produce relevant impacts regarding river morphology and related environmental services. This study shows that hydro-morphodynamic modeling tools can be used to optimize dredge-and-dump activities and, at the same time, mitigate problems deriving from these activities in rivers. As a case study, we focused on dredging activities on the Lower Parana River, Argentina. Navigation on this river is of crucial importance to the economies of the bordering countries, hence, each year significant dredging activities are employed. To estimate dredging loads under different strategies, a 25 km river reach of the Parana River was modeled using the Delft3D-modelling suite by Deltares. The Netherlands, to simulate flow-sediment interactions in a quasi-steady and uncoupled approach. Impacts of dredging activities were explicitly included. Different dredge-and-dump strategies included variations in dredging over-depth (clearance) and variations in dumping locations. Our results indicate that dredge-and-dump strategies can be targeted to stimulate natural processes that improve the depth and stability of the navigation channel and to counteract unwanted bed level responses in the long-medium term. A ~40% reduction in dredging effort could be achieved by moving the dredged material to distant locations in the secondary channel rather than dumping to the side of the waterway in the main channel.