Geomorphological modelling has evolved significantly the representation of the link between river morphology, flow processes and sediment transport; notably recently, with an emphasis upon the interactions between vegetation dynamics and morphodynamics. Nevertheless, vegetation dynamics have tended to be treated as a simplistic “black box” in which time replaces the more complex underlying processes. Thus, riparian vegetation dynamics not only result from interactions between surface-flow, topography and vegetation resistance to disturbance, but also soil development within the fluvial zone, which affects nutrient and water supply. This interplay between vegetation, soil and hydrogeomorphological processes is generally labeled the Fluvial Critical Zone (Figure1).
Figure 1: Conceptual model of the Fluvial Critical Zone, showing the feedback between soil, vegetation and hydro-geomorphology (Ashworth and Ferguson, 1986; Bullinger-Weber et al., 2007; Fisher et al., 2007; Gerrard, 1995; Glenz et al., 2006; Gurnell et al., 2001).
Quantifying the co-evolution of this system (Figure 2) on a braided river reach over a time scale of decades is crucial to understand how riverine landscapes respond to increasing human pressure and to climate change. Integrating the Fluvial Critical Zone into hydro-geomorphological models will than give the tool to better assess system transitions and develop sustainable management practices.
Figure 2: Hypothetical co-evolution for a fluvial landform following the Fluvial Critical Zone.
