Morphological Adaptation of River Channels to Vegetation Establishment: A Laboratory Study

Abstract

While the scientific community has long recognized that alluvial rivers are the product of interactions between flowing water and bed material transport, it is increasingly evident that vegetation mediates these interactions and influences the stream channel characteristics. In a novel set of mobile bed laboratory experiments with variable discharge, we demonstrate that vegetation colonization affects bank erosion rates, channel shape, channel sinuosity, and bar pattern. Our analyses compared the morphological evolution of channels with initially steady bars considering the following three scenarios: (1) channel without vegetation, (2) channel with vegetation added to the floodplains, and (3) channel with vegetation added to both the floodplains and the bar surfaces that emerge at low flows. Absence of vegetation produced the widest and shallowest channel with the lowest sinuosity. Floodplain vegetation in the second scenario reduced bank erosion and resulted in a deeper and more sinuous channel with shorter bars. In the third scenario, vegetation establishment on emerging bar surfaces intensified erosion on the opposing bank, enlarging the amplitude of bends. Enhanced sedimentation on vegetated bar areas increased both bar elevation and bar length compared to the second scenario. The results show that the colonization of bar surfaces by plants creates the conditions for new floodplain and island formation, fostering channel meandering and anabranching. Finally, our experiments emphasize the role of alternating high and low flows on the morphological development of streams mediated by vegetation.

Predicting deformations in the area of impact exerted by a bridge crossing based on the proposed mathematical model of a floodplain flow

“…The proposed approaches [7][8][9][10] to studying the processes of floodplain flow formation correspond to their natural state, rather than the artificially compressed state. The presented results of the numerical experiment allow studying the development of deformations on floodplains, in particular, in the zone of influence of a bridge crossing taking into consideration peculiarities of relief and interaction with the watercourse flow on actual objects of transport facilities.…”

“…According to the above [7] results of laboratory research with a movable vegetation layer, deformation development rate, the formation of a floodplain flow and of the relief of floodplains themselves are caused by vegetation distribution, growth and origin. The lack of vegetation contributes to the flow formation with the smallest winding, river vegetation slows down the deformation development on floodplains and promotes watercourse deepening.…”

The role of vegetation and large wood on the topographic characteristics of braided river systems

“…Our results are consistent with other recent evidence available in the literature. Vargas-Luna et al (2019) showed that vegetation encroaching on a sinuous sand-bedded channel in flume experiments caused the main channel to become deeper and the bars to increase in elevation because of sedimentation. Similarly, Lightbody et al (2019) Despite the limits of simplifying natural river processes in a flume experiment, it seems quite relevant that the topographical nature of a river system forced by vegetation is consistently different in terms of the vertical distribution of elevations and synthetic indexes of semivariograms, if compared with what is measured in a braided river without vegetation.…”

Along‐Stream Variations in Valley Flank Erosion Rates Measured Using 10Be Concentrations in Colluvial Deposits From Canyons in the Atacama Desert

“…Conversely, bank height may limit bank erosion (Bufe et al., 2019). Vegetation is known to increase the cohesion and to limit the erosion of channel banks (Vargas‐Luna et al., 2019), to slow down the lateral mobility of meanders (Lelpi & Lapotre, 2020), and to increase the minimum stress that needs to be overcome in order to detach blocks from the flanks (Langston & Temme, 2019).…”