A Simplified Simulation Method for Flood-Induced Bend Scour—A Case Study Near the Shuideliaw Embankment on the Cho-Shui River

Abstract

Abstract:The modeling of flood-induced bend scour near embankment toes can provide important information for river engineering, embankment safety warnings, and emergency action management. During the rainy seasons, short-term general scour and bend scour are the most common causes for the failure of reinforced concrete embankments in Taiwan. To gain a deeper understanding of the scouring process near embankment foundations, this study proposed a straightforward and practical method for bend scour simulation. The proposed simulation method is subdivided into three stages: two-dimensional flow simulation, general scour estimation, and bend scour estimation. A new bend scour computation equation is proposed and incorporated into a two-dimensional hydraulic finite-volume model for simulating the evolution of bend scour depth around embankment toes. The proposed method is applied to simulate the temporal evolution of bend scouring near the Shuideliaw Embankment on the Cho-Shui River in Taiwan, where serious failure occurred during the June 2012 monsoon. Field data were gathered using the numbered-brick technique at the Shuideliaw Embankment to demonstrate the accuracy of the proposed method. The results of the bend scour simulations compared reasonably well with field measurements, indicating close agreement in terms of water levels and bend scour depths near the Shuideliaw Embankment. The proposed method was found to quickly estimate the maximum short-term general scour and bend scour depths for further enhancement of the safety of the embankment toe.

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

“…To develop a reliable equation for the maximum scour depth in a river bend, Guo et al [19] collected field data for short-term bend scour in Taiwan and proposed a practical computation equation. More bend scouring field data have become available; thus, the computation equation from Guo et al [19] can be reconstructed. Hong [21] introduced a concept of effective flood peak duration (tp) to determine the following physical parameters:…”

“…Equation (17) should enable more accurate predictions than laboratory-based equations because it is based on specific field data in Taiwan. In addition, it is easy to apply in 1D and 2D numerical algorithms because of the concept of approach flow [19]. The data ranges for Equation 17 17are used to predict bend scour depth.…”

“…When modeling the bend scouring caused by floods, a challenge is to develop a numerical model that accurately consider physical processes of scour. Therefore, Guo et al [19] proposed a simplified simulation method for simulating flood-induced embankment toe scouring in bend reaches. The method involves the use of two models: one predicts a 2D flow field and the other estimates the temporal evolution of bend scour depth near the embankment.…”

“…Moreover, methods for embankment toe protection could be considered for enhancing the practical applications of scour models in the riverbank failure assessment. In the present study, the simulation method by Guo et al [19] will be extended to link with 1D model for predicting river embankment failure caused by toe scour.…”

“…The purpose of this paper is to present a novel bend scour simulation model based on the simulation method reported by Guo et al [19]. The present scour model integrates the 1D module of the WASH123D (Watershed Systems of 1-D Stream-River Network, 2-D Overland Regime, and 3-D Subsurface Media) model [20], hereafter referred to as the WASH1D model, the SFM2D (shallow-water finite-volume model) [19], and a predictive equation of bend scour depth [21]. Through the boundary connection of 1D-2D models, it is possible to achieve more accurate flow and scouring at embankment toe and apply the 1D model elsewhere in the river reach.…”