Experimental and Numerical Approaches to Overtopping Levee Breach Effects in a River and Floodplain

Abstract

This paper described the results to identify, characterize, and simulate the levee breach effects in a river and floodplain by overtopping. One-side levee model is built in a laboratory experimental flume as well as numerical simulation using sand with proper compaction. An initial condition provided for the overflow breach is considered with partial crest opening. Small-scale laboratory experiments were performed to evaluate the effects of overtopping levee breaching and investigated simultaneous phenomena appears in a river, levee and floodplain, and validated the results with same scale numerical simulations; and the results of both approaches were in conformity. The failure behavior of an earthen levee focuses on the effects of material sizes, river bed slopes and bed variations relative to floodplain. According to the results, the higher bed level brings more rapid propagation of the levee breach and widening with more sediment deposition in the floodplain area as well as river bed degradation in the upstream of the levee breach point may cause further risk of the levee breach during the next flood. Using finer bed materials, river bed deformation and sediment deposition in the floodplain are clearly make differences with coarser materials, also it create the normal flow problem through the river in future.

New Hypothesis for the Final Equilibrium Stage of a River Levee Breach due to Overflow

“…Further laboratory and numerical experiments were conducted with a focus on the effects of grain size (Islam & Tsujimoto, 2015), riverbed elevation, material and slope (Bhattarai et al, 2015), and inflowdownstream conditions (Rifai et al, 2017) on the levee breach development. However, no systematic study on the final breaching stage is available, so that the existence of a final equilibrium could not yet be adequately addressed.…”