The Rhythm of Rivers - On Dune Dynamics and Hydraulic Roughness

Summary

River deltas are influenced by both the currents from the sea and from the river, driving the delta morphology. Deltas worldwide face the threat of relative sea level rise, putting their dense population in danger. Operational water management to predict the behaviour of the rivers in these densely populated areas is essential. Water is managed by the use of hydraulic models, and one of the essential parameters in these models is hydraulic roughness, or in other words, the resistance the water experiences by protruding objects. The main source of this resistance was thought to be river dunes: subaqueous undulations on the river bed. Therefore, this thesis aimed to determine what impacts the geometry of
these river dunes, and how the river dunes in turn impact the hydraulic roughness in the deltas. This thesis shows which environmental factors impact the dune geometry, and it underlines that, despite being very important for many other fields, details in dune geometry are less important for large-scale friction than previously thought.