River Dune Behavior in Dredged Areas.

Safe navigation in rivers often requires repeated dredging operations. River dunes are causing shallow areas, so a better understanding of dune behavior can aid decision‐making on dredging strategies. A new dune‐tracking method was developed to analyze dunes after dredging. This knowledge was combined with information on dredging methods and intensity. This enables the analysis of dune development after dredging and the assessment of the impact of dredging methods such as topping (removing sediment from the crest) and swiping (transferring sediment from the crest to the trough). The results show that dredging increases the growth rate of dunes, especially when the discharge increases after dredging. For the studied dredging intensities, topping has a more pronounced effect than swiping on the immediate reduction of dune height. The changes in dune heights due to dredging are within the natural dune height variability. In the long term, topped dunes exhibit larger growth rates than those undergoing swiping. So dredging does have an effect on dune dynamics, in particular on the dune height growth rates. Plain Language Summary: River dunes are bedforms in the river bed that can create shallow areas, which may hinder navigation. To keep the shipping channel deep enough, regular dredging is needed. A new method to track these dunes was developed to examine the impact of two dredging methods on the dune development: topping (removing sediment from the top) and swiping (moving sediment from top to trough). The results show that dredging when water levels are increasing, results in increased dune height growth rates. Dredging when water levels are lowering can result in both increased and decreased growth rates, while in this case the dredging helps the dunes to change to their eventual lower height. Among the dredging methods studied, topping reduces the height of the dunes more than swiping. But in the long run, dunes that have been topped tend to grow back bigger compared to those that have been swiped. Dredging does influence river dune dynamics, but the effect on dune height is similar to variability in dune height that occurs naturally. The study helps us understand better how different dredging methods impact these river dunes, which can help in planning better ways to keep rivers safe and easy to navigate. Key Points: Applying a two‐dimensional wavelet filter on dunes allows for reliable dune tracking with cross‐correlationDredging results in an increased dune height growth rate when the discharge increasesThe dredging method, that is, topping or swiping, matters for the recovery of the dunes [ABSTRACT FROM AUTHOR]