Experimental study on the process of neck cutoff and channel adjustment in a highly sinuous meander under constant discharges

Li, Zhiwei; Wu, Xilong; Gao, Peng

doi:10.1016/j.geomorph.2018.11.002

Cited by 19 publications

(9 citation statements)

References 55 publications

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“…5j). Similarly to laboratory tests performed by Li et al (2019), our experiments exhibited increased eroding and reworking of channel banks when increasing the slope and discharge (tests 2 and 3; see, e.g., Figs. 4c and 5i).…”

Section: Discussionsupporting

confidence: 72%

“…The research tasks included: (i) to track the evolution of river planform in various flow and sediment delivery conditions, and (ii) compare the results of the flume experiments with the evolution of real river courses. Previous research based on flume tests aimed, e.g., to simulate the influence of vegetation on bank stabilization and formation of a meandering planform (Tal and Paola 2007;Braudrick et al 2009), and the influence of flow variability and presence of fines on the prevention of erosion and bank stabilization (Métivier et al 2016), and formation of meandering rivers and cutoffs (e.g., Schumm and Khan 1972;van Dijk et al 2012Li et al 2019). In our flume tests, we decreased the magnitude of discharge (test 1), simulated flood events by temporal increase of the flow (test 2), and floods accompanied by additional sediment load (test 3) to track processes taking place in rivers affected by such events.…”

Section: Introductionmentioning

confidence: 99%

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The influence of changes in flow regime caused by dam closure on channel planform evolution: insights from flume experiments

et al. 2021

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Constructions of dams influence river courses by cutting off sediment delivery and altering flow regime. We conducted flume experiments to study how sediment starvation, flow deficit and occurrence of series of floods with sediment load influence the evolution of channel planform. Results indicated that reduced flow caused a transition from a braided to incised single-thread planform with remains of inactive channels. The planform resembled rivers suffering from flow reduction caused by dams and constructions of irrigation canals (e.g., Central Platte River, USA). Simulation of series of floods with no sediment delivery caused the formation of an anabranching planform with incised main channel, alluvial islands, and side channels active at high flows. This evolution corresponds to river courses altered by sediment starvation and series of floods (e.g., the lower Drava River, Hungary). Floods with delivery of fines created a single-thread, incised channel with terraces along banks. Such channels are formed by rivers closed by dams, and compensating sediment deficit by sediment load from tributaries and/or floodplains (e.g., the Green River, USA). The flume tests demonstrated how flow and sediment deficit influence river channels and that the potential for restoration strongly depends on possibilities for the activation of sediment supply. However, restoration of pre-dam conditions is often impossible owing to other hydro technical works and land use changes. The highest restoration potential refers to the rivers compensating sediment delivery blocked by dams with tributary and floodplain resources.

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Section: Discussionsupporting

confidence: 72%

Section: Introductionmentioning

confidence: 99%

The influence of changes in flow regime caused by dam closure on channel planform evolution: insights from flume experiments

et al. 2021

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“…For example, riparian vegetation (Simon & Collison, 2002), pore water pressure (Deng et al, 2018; Rinaldi et al, 2008), seepage flow (Rinaldi & Nardi, 2013), fluvial erosion (Motta et al, 2014), and bank stratification (Lai et al, 2015) have all been shown to play a major role in bank morphodynamics. In previous physical experiments, bank collapse/erosion has been suggested to be a trigger for river bank retreat, channel meandering, and cutoff (Braudrick et al, 2009; Dulal & Shimizu, 2010; Friedkin, 1945; Li et al, 2019; Li & Gao, 2019; Schumm & Khan, 1972; van Dijk et al, 2012; Visconti et al, 2010). Subsequently, many studies were carried out to analyze the failure mechanism of bank collapse in response to different driving forces.…”

Section: Introductionmentioning

confidence: 99%

Laboratory Experiments of Bank Collapse: The Role of Bank Height and Near‐Bank Water Depth

et al. 2020

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We set up a laboratory experiment to reproduce flow-induced bank erosion and bank collapse and to study the role of bank height (H b ) and near-bank water depth (H w ) on bank stability. Five laboratory experiments were conducted in a plexiglass-walled soil tank, using silt collected from natural tidal channel banks (D 50 = 75 μm). During each experiment, the bank was subject to a steady and uniform flow. We measured the variations in total soil stress, pore water pressure (when negative, called matric suction), and water content inside the bank and flow velocity and suspended-sediment concentration upstream and downstream of the bank. Results show that the experiments can reproduce four failure types commonly observed in nature including toppling, tensile and shear failures, and erosion and failure driven by loss of matric suction. The patterns of bank failure can be related to H b /H w . For large H b /H w (> = 2), we observe a cantilever-shape bank profile. For small H b /H w (<2), we first observe cracks on the bank top, followed by shear failures along a vertical or inclined surface separating the cantilever block up from the bank top. When accounting for our results in the context of previous experimental studies, we find a transition point characterized by a maximum normalized bank retreat rate. For toppling failures, we also find a positive correlation between the ratio H b /H w and the geometrical contribution to bank retreat from bank collapse (C bc ). Our research quantifies the role of H b /H w on bank collapse, bank retreat rate, and the overall C bc .Plain Language Summary The stability of river banks is a key process in river morphodynamics and of great relevance to river engineering and management. Progress in this area of research is hampered by the difficulty in obtaining measurements. Bank collapse is in fact a fast and often massive event, which is difficult to capture in the field. Using sediment collected next to a channel experiencing bank retreat, we set up a laboratory experiment to study and quantify the effect of the geometry of the channel on bank stability. Our experiments resulted in different types of bank collapse and indicate that the ratio between the height of the exposed part of the bank (bank height) and the height of the submerged part of the bank (near-bank water depth) controls bank stability. The role of the ratio between bank height and near-bank water depth has been long neglected, but our study shows that it plays a major role on bank collapse and retreat and so on the morphodynamic evolution of the entire channel.

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“…On the other hand, it results in an uncontrolled channel reach created , which develops into an oxbow lake. Furthermore, neck cut-off increased bank erosion and channel widening in both upstream and downstream channels, owing to the fact that it raises sediment supply rates in upstream cases and limits the river's capacity downstream due to sediment-laden flow (Li et al, 2019). that interact and interrelate in global direct bank line migration (Nabi et al, 2016).…”

Section: Change Of Neck Lengthmentioning

confidence: 99%

Morphological characteristics and changes in the Upper Reach Gumara River in Ethiopia from 1957 to 2020

Melsse

Tegegne

Zewudu

et al. 2022

Preprint

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Human intervention with the natural landscape, including various river systems, is increasing in most parts of our country due to population growth and their infinite demand. As a result of this, the river system was jeopardized, causing irreversible damage to the socioeconomic and infrastructural systems. Morphological characterization and change evaluation of rivers are essential prerequisites for investigating their historical evolution and making reasonable estimates about how rivers might adapt to changing natural conditions and increasing anthropogenic impacts. This study focuses on the upper reach of the Gumara River along a 47.336 km stretch because it is a highly meandering and dynamic fluvial system with minor natural and anthropogenic influences that harm living and nonliving things around the flow path. We use satellite images as a data source, and the study reach was divided into six sections based on the waterway geometry and various forms of human intervention along the river, for detailed river morphological characterization and change detection, and to know the disturbance that facilitates the change in sub reach. In addition to satellite imagery, field observations, informal interviews with local indigenous people, laboratory analysis of bank material, and Meteorological and Hydrological data were used. The primary goal of this study was to assess the Morphological Characteristics and Change of the Upper Reach Gumara River over a 64-year period in Tana Basin, Ethiopia. Image analysis software (ERDAS Imagine 2015 and Arc GIS 10.5) was used for data preparation and analysis, and to characterize and detect the change of study reach, various morphometric parameters such as Sinuosity index, braided index, River center line, actual River length, river width, meander neck length, and River area were determined. From the entire period of 64 years of sinuosity index analysis, the sinuosity was increased by 5.49%. The section between five and six had a 63% reduction in neck length. Over a 64-year period, the overall width increased by 0.348 m per year. All of the morphometric parameter results and social information show that the upper reach of the Gumara River was dynamically changed and disrupted the surrounding socioeconomic system, implying that critical measurements should be designed and implemented.

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Experimental study on the process of neck cutoff and channel adjustment in a highly sinuous meander under constant discharges

Cited by 19 publications

References 55 publications

The influence of changes in flow regime caused by dam closure on channel planform evolution: insights from flume experiments

The influence of changes in flow regime caused by dam closure on channel planform evolution: insights from flume experiments

Laboratory Experiments of Bank Collapse: The Role of Bank Height and Near‐Bank Water Depth

Morphological characteristics and changes in the Upper Reach Gumara River in Ethiopia from 1957 to 2020

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