Experimental and Numerical Modeling of Overhanging Riverbank Stability

Abstract

induces salt-marsh loss (Deegan et al., 2012) and thereby affects the global carbon cycle (Kirwan & Mudd, 2012), and modulates the diversity of fluvial habitats (Piégay et al., 1997). According to the driving forces, bank retreat is commonly classified into flow-driven bank erosion and gravity-driven bank collapse (Simon et al., 2000;Thorne, 1982), and the latter can be further classified as slide and cantilever failures. Cantilever failure is usually observed when sediment entrainment by surface and seepage flow takes place at the lower bank (e.g., composite riverbanks, salt-marsh edge, and tidal channels), leading to the formation of an overhanging bank profile (

A Review on Bank Retreat: Mechanisms, Observations, and Modeling

“…Extending the experimental analysis to a broader range of values of the ratio H w / H b , K. Zhang et al. (2021) further pointed out the need to include water content variation when predicting shear or toppling failure. Their experimental framework provides a new way to predict failure patterns by combining hydraulic and geotechnical control factors.…”

“…Midgley et al (2013) reported that seepage erosion became temporarily restricted after bank collapse, since the collapsed bank soil blocked flow pathways and limited particle mobilization. From a morphodynamic perspective, collapsed bank soil abruptly alters the local topography and the flow resistance of the near-bank channel bed (K. Zhang et al, 2021), possibly generating complex turbulence at the bank toe and affecting the cross-sectional evolution of channels. Based on three-dimensional flow field observations, C. Hackney et al (2015) stated that collapsed bank soil may also deflect flow onto the bank, thus enhancing bank erosion rate.…”

“…This finding can be partly explained by a dynamic equilibrium theory (Zhou et al., 2017) whereby bank dynamic is not only associated with a monotonic retreat, but is possibly characterized by a periodic cycle of erosion and accretion (e.g., the catch‐up behavior reported in meander migration (Mason & Mohrig, 2019; Nanson & Hickin, 1983; Zhao et al., 2021)). In other words, when considering the bank retreat rate over relatively long‐time periods, other dynamics such as subaerial processes prior to bank erosion/collapse (e.g., freeze‐thaw and drying‐wetting cycles) (Chassiot et al., 2020), decomposition of collapsed bank soil (C. Hackney et al., 2015; Fagherazzi et al., 2004; K. Zhang et al., 2021), and bank accretion (Asahi et al., 2013) can all lead to a lower than expected bank retreat rate. The issue associated with the choice of a suitable temporal scale thus turns out to be crucial, since it determines the robustness and accuracy of the developed empirical relations given the period of time to be considered for predicting the bank dynamic (Hooke, 1980; J. Pizzuto et al., 2010).…”

“…The role of soil pore‐water pressure has been long neglected in numerical modeling. Only a few studies have been conducted to explore the interactions with other factors (Darby et al., 2007; Deng et al., 2018; K. Zhang et al., 2021). For instance, Darby et al.…”

“…Stress‐strain analysis has been developed to account for any deformation of bank material during bank collapse and has been applied to both fluvial and tidal contexts (Gong et al., 2018; K. Zhang et al., 2021; Masoodi et al., 2019; Samadi et al., 2013; Zhao et al., 2019, 2021). In the case of fluvial environments Samadi et al.…”