Investigation of Scour Pattern Downstream of Levee Toe Due to Overtopping Flow

Abstract

Levee overtopping creates large scoured region at the landside, which greatly affects the levee performance. Both 3D and 2D experiments were conducted to analyze the downstream scour profile after levee overtopping. For elucidating the difference of scour pattern under various overtopping water depth and width conditions, 3D scour profiles are investigated. In addition, vertical 2D scour profiles are also investigated to compare the 3D scour profiles with 2D experiment results. From the analysis, it has been observed that for overtopping width (W bank ) to levee height (h bank ) ratio of 6 to 8, multiple scour holes appear with overtopping height (d bank ) to levee height (h bank ) ratio of 0.1 to 0.2, while for same W bank /h bank , two scour holes are created when d bank /h bank =0.25 to 0.3. Comparison of 2D and 3D scour data sets at downstream scour profiles shows that 3D experiments tend to create larger scour depth and shorter scour length than 2D cases. This result indicates the importance of 3D experimental analysis for levee design..

Three Dimensional Downstream Scour Analysis After Levee Overtopping

“…4(b), where experiment was conducted in 2D setup with 10cm levee height condition while other experimental conditions being similar to the present research. Scour depth was observed higher in case of 3D experiments compared to 2D experimental cases 5) . Rest of the previous studies, plotted in Fig.…”

“…Scour length results of 2D cases from other researchers 5),9), 14) are larger than the calculated scour length results following Eq. (5) for 3D cases of the present study due to absence of lateral flow dispersion 5) . For defining non-dimensional scour width (S w /h bank ), multiple regression analysis has also been conducted using the data in present 3D experiments.…”

“…4(a)). Non-dimensional 2D scour depth results 5) are plotted in Fig. 4(b), where experiment was conducted in 2D setup with 10cm levee height condition while other experimental conditions being similar to the present research.…”

“…Three dimensional scour analyses is very important for levee design, as in case of 3D experimental analysis scour depth was found to be higher compared to the 2D experimental analysis under similar experimental conditions 5) . Pagliara 6) also observed larger scour depth in a symmetrically expanding stilling basin.…”

Experimental Study on Scouring and Deposition Characteristics of Riprap at Embankment Toe Due to Overflow

“…Scour at the landside toe of the embankment during overtopping flow is one of the main reasons for the fragility of the embankment slope and levee breakage [3,4]. The initial scour depth, plunge pool height, and subsequent headcut migration are responsible for the breakage mechanism of the embankment and the total time required for complete failure of the embankment [5,6].…”