Coupled modeling of bank retreat processes in the Upper Jingjiang Reach, China

Abstract

Bank retreat processes in the Upper Jingjiang Reach (UJR) have attracted much attention in recent years due to a high occurrence frequency, and these processes can be influenced significantly by the near‐bank fluvial erosion and variations in river stage and groundwater level. A coupled model was thus proposed in this study, integrating the module of bank‐toe deformation with the modules of groundwater level change and bank stability analysis. The proposed model was validated through comparisons between the calculated and measured bank erosion volumes and bank profiles at four typical sections in the UJR, with relatively close agreement being obtained. Multiple tests were conducted to investigate the model performance. These results show that: (i) a more rapid drawdown of river stage resulted in a more significantly delayed response of groundwater level to river stage, indicating that the bank may suffer a higher pore water pressure at the same river stage during the rapid drawdown period; (ii) a larger bank erosion volume was predicted, with the delayed response of groundwater level being considered. In addition, initial groundwater level may take a great impact on bank erosion simulations, especially for the banks with relatively lower soil permeability and shear strength); (iii) based on the adopted method of bank stability analysis, the occurrence of the first failure may greatly influence the sequential failures, and thus the total number and volume of bank failure; (iv) the calculated bank erosion volume was most sensitive to a change in the critical shear stress, especially to its decrease, when the erodibility coefficient was determined by an empirical function of the critical shear stress. © 2018 John Wiley & Sons, Ltd.

Downstream geomorphic impact of the Three Gorges Dam: With special reference to the channel bars in the Middle Yangtze River

“…Frequent bank erosion in many local reaches (without bank protection engineering) has been observed in the post-dam period (Xia et al, 2016), which was harmful to local bank stability and flood control through the loss of land and destruction of bank protection structures (Darby et al, 2002;Hooke and Yorke, 2011). Post-dam bank erosion is mainly caused by channel incision (Petts and Gurnell, 2005) and variations in the intra-annual flow regimessuch as the rapid drawdown in water levels in September and October during the recession stage of the TGD (Darby et al, 2002;Deng et al, 2018). Furthermore, climate changein particular the increased variability of the eastern Pacific El Niño under greenhouse warming (Cai et al, 2018)can increase the frequency of extreme rainfall in the Yangtze River basin, as is evident in the catastrophic floods of 2015 and 2016 (Li and Lu, 2017;Mei et al, 2018).…”

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

“…Bank erosion is of fundamental importance to the morphodynamics of fluvial, estuarine and coastal environments, affecting a wide range of physical, ecological, and socioeconomic processes. Bank erosion drives channel width changes (Deng et al, 2018; Deng et al, 2019; Eke et al, 2014; Lopez Dubon & Lanzoni, 2019; Zhao et al, 2019), serves as a major source of sediment load creating riparian habitats (e.g., floodplain and alternate bar) (Daly et al, 2015; Florsheim et al, 2008), and induces farmland and wetland loss (Deegan et al, 2012; Qin et al, 2018; Turner, 1990). Bank erosion is commonly categorized into flow‐induced bank erosion and bank collapse (Simon et al, 2000; Thorne & Tovey, 1981).…”

The Role of Collapsed Bank Soil on Tidal Channel Evolution: A Process‐Based Model Involving Bank Collapse and Sediment Dynamics

“…In terms of model limitations, results of Gong et al (2018) show that the loss of hydrostatic pressure during ebb tide promotes the occurrence of bank collapse, consistent with Simon et al (2000). However, Deng et al (2018) argued that pore water pressure resulting from the transition between saturated and unsaturated soil rather than hydrostatic pressure triggers bank failure. The increased pore water pressure resulting from rapid decrease in channel water level significantly weakens bank stability.…”