| Rivers self-organise by forming and destroying channels, banks and floodplains. Distinctive river patterns emerge in nature such as braided, wandering or meandering. Generic experimental setups or physics-based numerical models that can produce all patterns do not exist. This reflects the lack of quantitative understanding how feedbacks between the channels and self-formed banks and floodplains lead to these river patterns. This understanding is urgently needed to predict the rivers? response to natural and man-induced changes in forcings, notably climate change, land use change, river restoration and flood mitigation works. The objective is to understand and quantify how feedbacks between self-forming levee-floodplain complexes and the channel(s) lead to dynamic pattern characteristics, and how these patterns adapt to changes in forcings. Many fundamental fluvial processes are relatively well understood, but their combined effect on river pattern remains hypothetical. For weak banks braided rivers emerge whereas for strong banks meandering rivers emerge. Vegetated levees and cohesive floodplains provide strength to eroding channel banks. This strength determines width-depth ratio and bar pattern. Bar pattern, in turn, determines the pattern of bank erosion during floods, which may lead to a meandering planform. I will generate distinctive river patterns by applying appropriate boundary conditions to laboratory experiments and a physics-based numerical model. In experiments, floods will be imposed, vegetation will be grown and a polymere and natural sediment mixtures will be supplied in various combinations for flexible scaling of bank strength and floodplain deposition. I will extend a three-dimensional numerical model with bank erosion, cohesive floodplain sedimentation and effects of vegetation. I will then model equilibria and system response to changing forcings on time scales up to centuries on parallel computers. Finally, I will integrate experimental and modelling insights and verify these with detailed data of the Rhine, Allier and Saskatchewan rivers through dedicated modelling. |
