Where river and tide collide: Ebb and flood channels approximated as asymmetrical river bifurcations

Abstract

Currently, ebb and flood channels which can be seen in natural systems are also present in numerical and physical models, but how these features develop is still largely unknown. In an estuary the division of the flood channel from the ebb channel might be seen as a bifurcation during flood and a confluence during ebb due to the flow reversal. Channel networks from four different data sets were extracted from bathymetric maps, to study the possible link between the elevation jump and bifurcation angle in ebb and flood channel bifurcations, to see if the link is the same as in river bifurcations. Two physical models (Metronome) and two numerical models (Western Scheldt, Delft3D) were used. One data set from each model was dredged, the other autonomous. The channels in the networks are divided into different scales based on the amount of sediment that is allowed to erode from source to sink. This produced one main channel and lower scale bifurcating channels. The beginning and endings of ebb and flood channels are predicted corresponded with literature on river bifurcations. There seems to be no difference between a dredged or an autonomous system. Bifurcation angle and elevation jump of ebb and flood channels can be approximated as river bifurcations.