Bedform characteristics during falling flood stage and morphodynamic interpretation of the middle–lower Changjiang (Yangtze) River channel, China

Multibeam Bathymetric Investigations of the Morphology and Associated Bedforms, Sulina Channel, Danube Delta

“…Bridge and Best [56] presented preliminary results from an experimental study of the interaction between turbulence, sediment transport, and bedforms dynamics over the transition from dunes to upper stage plane beds. All of the observed bedforms had a mean length of 0.7-0.8 m. Chen et al [16] described bedform characteristics in the mid-lower Changjiang River. The authors distinguished four types of bedforms, including flat bed, megaripple, small dune, and large dune, mostly in equilibrium with present flow conditions; only the large bedforms were relicts of the previous large discharges.…”

“…The fluvial environment was investigated by many authors in order to describe the bed morphology and bedforms migration [5,[8][9][10]13]. Many studies of the bedforms classification, behaviour, and evolution can be found in the literature [14][15][16][17][18][19][20][21]. Bedform geometry is shown to be influenced by transport stage [20][21][22], by sediment concentration in flow [23], and is dependent on how sediment is transported by flow [5,24].…”

“…Numerical simulations on dune evolution and dune migration are also available [6,[26][27][28]. Using van Rijn's classification [20] on the Yangtze River, Chen et al [16] measured dunes with maximum length of 300 m and up to on dune evolution and dune migration are also available [6,[26][27][28]. Using van Rijn's classification [20] on the Yangtze River, Chen et al [16] measured dunes with maximum length of 300 m and up to 8 m in height.…”

“…Using van Rijn's classification [20] on the Yangtze River, Chen et al [16] measured dunes with maximum length of 300 m and up to on dune evolution and dune migration are also available [6,[26][27][28]. Using van Rijn's classification [20] on the Yangtze River, Chen et al [16] measured dunes with maximum length of 300 m and up to 8 m in height. Small dunes were found by [15] on the Rhine River (L = 10-96 m and H = 0.3-1.4 m) and [29] on the Raba River (Poland) (L = 0.04-1.46 m and H= 0.04-0.12 m).…”

The Impact of Nonequilibrium Flow on the Structure of Turbulence Over River Dunes

“…The structure of flow over dunes whose morphology is in equilibrium with flow has been researched extensively in laboratory experiments (Bennett & Best, 1995;Best, 2005a;Fedele & Garcia, 2001;Kadota & Nezu, 1999;Kwoll et al, 2016;Lefebvre et al, 2016;Maddux et al, 2003;Mazumder et al, 2009;McLean et al, 1999McLean et al, , 1994Nelson et al, 1993;Nelson & Smith, 1989;Venditti, 2007) and simulated using Computational Fluid Dynamics (Chang & Constantinescu, 2013;Grigoriadis et al, 2009;Omidyeganeh & Piomelli, 2011, 2013a, 2013bOmidyeganeh et al, 2013;Stoesser et al, 2008;Xie et al, 2014), which has led to general agreement concerning the nature of the flow field over idealized dune forms, as outlined in conceptual models of flow over dunes (Best, 2005b; Figure 1). However, natural rivers rarely attain a flow morphology equilibrium due to temporal and spatial variations in hydraulic geometry leading to flow decelerations and accelerations, as well as varying discharge on a range of timescales (Aberle et al, 2010;Amsler & Garcia, 1997;Chen et al, 2012;Prent & Hickin, 2001). Consequently, the equilibrium description of flow structure over dunes encapsulated in Figure 1 might apply to natural channels only in rare instances.…”