Biomass selection by floods and related timescales: Part 1. Experimental observations

Several research investigations have explored the interaction between morphodynamic and vegetation growth processes from both the modelling and the experimental viewpoints. Results have mainly been concerned with morphologic analyses of the effects of vegetation on long term riverbed evolution without addressing the relative role of the timescales between such processes. This paper presents for the first time the statistics of uprooted biomass obtained while perturbing the vegetation growing in the river bed with periodic disturbances of constant magnitude. That is, we force the biological and hydrological processes to interact and study the related timescales in order to shed light on the role of flood disturbances in selecting the component of the biomass that has a higher chance of survival in relation to its growth stage. A simple interpretative stochastic model is then presented and thoroughly discussed in a companion paper (Biomass selection by floods and related timescales: Part 2. Stochastic modelling).

► Riverbed vegetation grows in non-cohesive sediment in relation to biological and hydrological timescales.
► At the laboratory scale we show how related processes interact and determine the resulting biomass distribution.
► Floods operate as selective mechanisms for plants depending on their root and canopy development.
► Biomass selection in relation to flood characteristics may thus occur within and among species.