Bank retreat plays a fundamental role in fluvial and estuarine dynamics. It affects the cross-sectional evolution of channels, provides a source of sediment, and modulates the diversity of habitats. Understanding and predicting the geomorphological response of fluvial/tidal channels to external driving forces underpins the robust management of water courses and the protection of wetlands. Here, we review bank retreat with respect to mechanisms, observations, and modeling, covering both rivers and (previously neglected) tidal channels. Our review encompasses both experimental and in situ observations of failure mechanisms and bank retreat rates, modeling approaches and numerical methods to simulate bank erosion. We identify that external forces, despite their distinct characteristics, may have similar effects on bank stability in both river and tidal channels, leading to the same failure mode. We review existing data and empirical functions for bank retreat rate across a range of spatial and temporal scales, and highlight the necessity to account for both hydraulic and geotechnical controls. Based on time scale considerations, we propose a new hierarchy of modeling styles that accounts for bank retreat, leading to clear recommendations for enhancing existing modeling approaches. Finally, we discuss systematically the feedbacks between bank retreat and morphodynamics, and suggest that to move this agenda forward will require a better understanding of multifactor-driven bank retreat across a range of temporal scales, with particular attention to the differences (and similarities) between riverine and estuarine environments, and the role of feedbacks exerted by the collapsed bank soil.

中文翻译：

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银行撤退回顾：机制、观察和建模

河岸退缩在河流和河口动力学中发挥着重要作用。它影响渠道的横截面演变，提供沉积物的来源，并调节栖息地的多样性。了解和预测河流/潮汐通道对外部驱动力的地貌响应是加强水道管理和保护湿地的基础。在这里，我们回顾了河岸退缩的机制、观察和建模，涵盖了河流和（以前被忽视的）潮汐通道。我们的审查包括对失效机制和堤岸退缩率的实验和现场观察、模拟堤岸侵蚀的建模方法和数值方法。我们发现，外力，尽管具有不同的特征，可能对河流和潮汐河道的堤岸稳定性产生相似的影响，导致相同的失效模式。我们回顾了一系列空间和时间尺度上河岸退缩率的现有数据和经验函数，并强调了考虑水力和岩土控制的必要性。基于时间尺度的考虑，我们提出了一种新的建模风格层次结构，用于解释银行撤退，从而为增强现有建模方法提出明确的建议。最后，我们系统地讨论了银行撤退和形态动力学之间的反馈，并建议推进这一议程将需要在一系列时间尺度上更好地理解多因素驱动的银行撤退，特别注意两者之间的差异（和相似之处）河流和河口环境，