Impact of flow variability and sediment characteristics on channel width evolution in laboratory streams

Abstract

Alluvial rivers are shaped by sequences of water flows excavating their channels. Observations show that besides the magnitude, the frequency and duration of streamflow oscillations might also be important for the river channel formation. In addition, the river morphology appears influenced by both size and degree of uniformity of the sediment. Nevertheless, many morphodynamic studies still represent the flow regime with a single value of the discharge, often corresponding to the bankfull condition, and the sediment with its median grain size. This work investigates the effects of streamflow variability and sediment characteristics on channel width formation, analysing the evolution of experimental streams with different sediments and discharge hydrographs. Results show that the formative condition of the channel width is not the geometric bankfull flow but a rather frequent peak flow. Remarkably different channel configurations arise from different sediment characteristics in the laboratory, where sediment non-uniformity produces more stable banks.

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

“…In addition to the latter, the experiments describe systems in which the discharge did not easily eradicate plants during high flow stages. Resistance to high‐flow uprooting is observed in small streams, like the Lunterse beek in the Netherlands (Vargas‐Luna et al, ). However, the experiments cannot be considered representative of large river systems, where plants have a less dominant role.…”

“…The sand used in the experiments had a median diameter, D 50 , of 0.001 m and was selected based on experimental work carried out by Byishimo () and Vargas‐Luna et al (). This previous research was focused on studying the effects of sediment properties and discharge variability on channel‐width changes and was vital to select the sediment used in these experiments.…”

Can Bankfull Discharge and Bankfull Channel Characteristics of an Alluvial Meandering River be Cospecified From a Flow Duration Curve?

“…Compared to the outer bank erosional process, the inner bank depositional process has been studied less (Güneralp et al, ). Inner bank point bar deposition is typically accelerated when vegetation colonizes the point bar (ASCE Task Committee, ; Gurnell et al, ; Vargas‐Luna et al, ). We consider a case for which the vegetation encroachment rate dominates the long‐term inner bank point bar depositional migration rate (Asahi et al, ; Eke, Czapiga, et al, ; Eke, Parker, & Shimizu, ; Parker et al, ).…”

“…Studies on hydraulic geometry relations indicate that a river organizes its bankfull geometry in a consistent way across the range of environmental settings (e.g., Leopold & Maddock, ; Li et al, ; Parker et al, ; Singh, ; Trampush et al, ; Wilkerson & Parker, ). Some experimental studies that utilize cohesive material or vegetation have demonstrated that self‐organized single‐thread channels can form so that the channel can just contain the supplied discharge without causing overbank spill (Tal & Paola, , ; Vargas‐Luna et al, ). Bankfull discharge has also been studied statistically; flood frequency analysis suggests that typical meandering rivers tend to be at bankfull state once in 1–2 years, or 1.5 years on average (Leopold et al, ; Dunne & Leopold, ; Wolman & Leopold, ).…”

Morphodynamic Trends of the Ribb River, Ethiopia, Prior to Dam Construction

“…Due to lack of measured data on river channel geometry and water levels along the river course, we apply here a flow frequency analysis based on Gumbel extreme distribution, assuming that the annual peak discharge is equal to the instantaneous peak discharge value of each year and that the discharges having return period of 1.5 and 2.0 years are representative for the bankfull conditions [34,36,37]. The maximum daily discharge of each year is filtered from the daily discharge time-series.…”