Predicting River Embankment Failure Caused by Toe Scour Considering 1D and 2D Hydraulic Models: A Case Study of Da-An River, Taiwan

Abstract

Physically based numerical models can predict scour depth at embankments located in bend reaches. However, methodologies for utilizing these numerical models to assess the risk of reinforced concrete embankment failure are rarely investigated. Therefore, a new assessment methodology is proposed to predict the riverbank failure caused by bend scour. The methodology is primarily based on a bend scour simulation model that integrates a one-dimensional (1D) hydraulic model, a two-dimensional (2D) hydrodynamic finite-volume model, and an empirical equation of bend scour prediction. The model was first applied to the Shuiwei Embankment located in a river bend reach of Da-An River in Taiwan and verified against results from the 1D hydraulic model and field data. The model was then used to simulate 2D flow field and the temporal evolution of bend scour depth under different return period flood events to examine the relationships between river discharge, water level, shear stress, and bend scour depth. The influence of shear stress on the stability of toe protections was also investigated. The field data (from two events) and numerical solutions (four scenarios) were assessed to conceive two empirical equations for predicting shear stress and bend scour depth. A new assessment methodology was proposed using these two equations to predict the risk of river embankment failure during flood periods. The proposed methodology can be easily applied in other disaster-prone regions to mitigate the effects of disasters caused by bend scouring.

Remote Sensing Methodology for Roughness Estimation in Ungauged Streams for Different Hydraulic/Hydrodynamic Modeling Approaches

“…Towards the investigation of Manning's n roughness coefficient estimation followed by the sensitivity analysis of floods using different hydraulic/hydrodynamic modeling approaches (1D, 2D, 1D/2D), several methodological approaches followed (Figure 1 According to the paragraphs mentioned above, it can be concluded that the objective determination of roughness coefficient in river flood modeling remains a crucial issue. Moreover, sensitivity analysis in flood inundation modeling using different hydraulic modeling approaches and/or combined with spatially distributed roughness coefficient maps is a subject that still concerns the scientific community [40][41][42][43]. The main purpose of this paper is to present an objective way to determine Manning's n roughness values, remotely-sensed estimated, and indicate how the changes in those values may affect a flood extent.…”