Modelling Floodplain Biogeomorphology

Abstract

Understanding the interactions between the ecosystem and the morphology of river floodplains, i.e. floodplain biogeomorphology, is becoming increasingly important in view of modern river management and climate change. There is a need for predictive models for the natural response of river floodplains to hydraulic measures and river rehabilitation, such as river widening, construction of secondary channels and floodplain lowering. This thesis investigates floodplain biogeomorphology from a modeller's perspective. It addresses management concepts such as room-for-the-river and cyclic floodplain rejuvenation, in which a symbiosis is sought for between flood management and nature rehabilitation, and it shows how 1-D, 2-D and 3-D numerical models can be used to support them. Its main focus is on one of the knowledge gaps emerging from these model applications, viz. the effect of floodplain vegetation on the bed shear stress and subsequent bedload sediment transport. By means of a combination of theory development, flume experiments and field work, this research has resulted into a number of practically applicable and validated formulations for the hydraulic resistance and bed shear stress reduction of vegetation. These can be applied in large-scale numerical morphodynamic models to better design river measures in combination with nature rehabilitation.