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Geomorphology and Flooding
Published in Saeid Eslamian, Faezeh Eslamian, Flood Handbook, 2022
Giovanni Barrocu, Saeid Eslamian
Braided rivers consist of an interlacing network of distributaries, which continually separate and reunite between shoals and islands of shingle and sand, with one channel usually being dominant. The floor and outer banks of the river bed, typically wide and shallow, are composed of loose sediments, generally deposited by rivers where they emerge from a canyon or ravine onto the bordering plane with a velocity suddenly checked by an abrupt gradient decrease.
Geologic Principles
Published in Stephen M. Testa, Geological Aspects of Hazardous Waste Management, 2020
Braided river systems consist of an interlaced network of low-sinuosity channels and are characterized by relatively steeper gradients and higher discharges than meandering rivers. Typical of regions where erosion is rapid, discharge is sporadic and high, and little vegetation hinders runoff, braided rivers are often overloaded with sediment. Because of this sediment overload, bars are formed in the central portion of the channel around which two new channels are diverted. This process of repeated bar formation and channel branching generate a network of braided channels throughout the area of deposition.
Surface water and the atmosphere
Published in Ian Acworth, Investigating Groundwater, 2019
It is imperative that the stage discharge relationship be determined over the widest possible range of flow conditions. Measurements at low to medium flow are often well constrained by repeated gauging; however, gauging at high flow is often difficult to achieve due to a lack of access. The rating curve becomes asymtopic to the x axis (flow) at high river stage and therefore inaccuracy in the stage has a major impact on discharge at high flow rates. The river gauging station where the river stage is measured should be selected in a section of the river where the flood is constrained to the river channel. This is typically not a problem in humid regions where rivers occupy permanent well-defined channels – but it becomes a severe problem downstream in flat and/or arid areas where braided rivers exist. A braided river may flow in one of several channels and will typically change the channel with little warning. A major flood will occupy the whole valley, but smaller floods may occupy one of several channels.
On some aspects of flow characteristics of the bifurcated channel – An experimental approach
Published in ISH Journal of Hydraulic Engineering, 2023
Amit Das, Bibhas Chandra Barman, Nityananda Nandi
Bifurcations are common features in anabranched reaches. Anabranched reaches may exist in meandering and braided rivers. A braided river is the one that contains a network of smaller channels separated by small islands called braid bars. An anabranched reach has more than one channel with a sequence of confluences and bifurcations and thus forms a multitude of islands in the river. A bifurcation occurs when a river splits into two branches as shown in Figure 1 or a middle bar form in a channel or a distributary carries flow from the main river. The course of a braided river is very unstable and unpredictable. This leads to serious problems for an engineer trying to tame the river with hydraulic structures. The morphological behavior and the effect of the bifurcation on the stability of the downstream branches strongly influence the stability of the braided river system as a whole. Flow and sediment distributions at bifurcations in braided channel systems are important for short- and long-term morphological development. A better understanding of the morphological processes at a bifurcation would contribute to the understanding of the behavior of a river. This would facilitate the task of the engineer trying to regulate the river.
Influence of erosion on piping in terms of field conditions
Published in Journal of Hydraulic Research, 2021
The horizontal pipes under the clayey dike do not realistically advance linearly from downstream to upstream. Van Beek (2015) showed that, at the beginning of the erosion process, pipe formation is similar to that of braided and/or meandering rivers (Figs 2 and 3). Because of horizontal pressure fluctuations, a braided river consists of a network of small pipes separated by small and often temporary islands called braid bars (e.g. Jansen et al., 1979). In addition to these effects, the influence of energy loss of both bifurcations (when a pipe separates into two or more pipes) and confluxes (when a pipe flows into two or more pipes) is neglected in the modelling and should therefore be examined in greater detail.
Channel bar development, braiding and bankline migration of the Brahmaputra-Jamuna river, Bangladesh through RS and GIS techniques
Published in International Journal of River Basin Management, 2022
Md. Bazlar Rashid, Md. Ahosan Habib
Many scholars around the globe conducted research on morphological characterization of big braided rivers through Geographic Information System (GIS) and Remote sensing (RS) techniques (Coleman, 1969; Gilfellon et al., 2003; Goswami, 1985; Islam et al., 2017, 2019; Khan & Islam, 2003; Langat et al., 2019; Lewin & Ashworth, 2014; Li et al., 2020; Mclelland et al., 2009; Negm et al., 2016; Nones, 2020; Richardson & Thorne, 1998). Morphological characteristics of any river including bar growth, the interconnection among the number of bars, bars area, river width, BI, sinuosity index (PT), etc. are very important variables for characterizing frequent, gradual, and rapid bankline migration and erosion (Ashmore, 1991; Bertoldi & Tubino, 2007; Chalov & Alexeevsky, 2015; Egozi & Ashmore, 2008; Rashid, 2020; Sarma 2005). Therefore, the present research is an attempt to delineate the morphological characteristics and their relation to bankline shifting and avulsion of the JR by using RS and GIS techniques. The prime objectives of the current work are to (1) delineate channel bar formation of the river; (2) estimate the braiding and sinuosity indices; (3) characterize the erosional and depositional distribution pattern of the river; (4) investigate the bank line migration pattern and (5) evaluate the probable causes of river bank erosion, course migration/channel shifting. It is profoundly expected that the obtained information of this article may be useful to future protective plans for sustainable development of the surroundings for setting up an appropriate routine erosion maintenance approach and the progress of suitable supervision plan for defending riverine marshlands affected by overstocking, local engineering structure, and increased runoff deviation aggravated by climate change.