Abstract
The planform morphology of a river reach is the result of the combined actions of sediment motion (erosion, transport and deposition), hydrological regime, development and growth of vegetation. However, the interactions among these processes are still poorly understood and rarely investigated in laboratory flume experiments. In these experiments and also in numerical modelling, vegetation is usually represented by rigid cylinders, although it is widely recognized that this schematization cannot reproduce the effects of root stabilization and binding on riverbed sediment. In this work, we focus on the effects of added vegetation on morphological dynamics of alternate bars in a straight channel by means of flume experiments. We performed laboratory experiments reproducing hydraulic conditions that are typical of gravel bed rivers, in terms of water depth, bed slope and bed load; these conditions led to the formation of freely migrating alternate bars. We then employed rigid vegetation that was deployed on the reproduced alternate bars according to field observations. Various vegetation scenarios, in terms of density and spatial arrangement, were deployed in the flume experiments such to mimic different maintenance strategies. Results show the effects of rigid vegetation on the alternate bar configuration on the overall topographic pattern, the main alternate bar characteristics (such as amplitude and wavelength) and migration rate.
Highlights
The whole scientific community agrees on the idea that spatial and temporal evolution of a river reach is governed by the mutual interactions among flow discharges, sediment transport processes and presence, growth and decay of riparian vegetation
We investigate the interactions between rigid riparian vegetation and freely migrating alternate bars in a straight channel
Each combination of flow discharge and bed slope was run until achieving the dynamic equilibrium of alternate bars in the channel: we defined such equilibrium when both sediment transport rate at the end of the flume was equal to the feeding rate and the wavelength of the alternate bars was constant
Summary
The whole scientific community agrees on the idea that spatial and temporal evolution of a river reach is governed by the mutual interactions among flow discharges, sediment transport processes (erosion, motion and deposition) and presence, growth and decay of riparian vegetation. They have still involved the simplifying hypothesis of vegetation as uniformly distributed rigid cylinders [7], which substantially limits the applicability of such models to real cases, when flexible juvenile plants are present[8]. In the last decades, river morphodynamics has been investigated by means of flume experiments including the biological component given by riparian vegetation by using either rigid cylinders [7, 9, among others] or real vegetation [10, 11] Results of such flume experiments reflect the unscaled effects of plants. The specific objectives concern the understanding of alterations induced by the presence of vegetation on the overall topographic pattern (and in particular on wavelength and amplitude) and migration rate of alternate bars
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
