Non-hydrostatic depth-integrated models for dam break flows through rigid-emergent vegetation

¹ Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima City, Hiroshima 739-8527, Japan
² Sohag Faculty of Engineering, Sohag University, Sohag 82524, Egypt
³ Department of Civil Engineering, Parahyangan Catholic University, Jl. Ciumbuleuit No. 94, Bandung, West Java 40141, Indonesia

^* Corresponding author: utida@hiroshima-u.ac.jp

Abstract

Dam failures can trigger catastrophic downstream flooding, threatening lives, and infrastructure. Vegetation acts like a natural dam break flow buffer, dissipating energy, reducing wave height and celerity. This highlights importance of vegetation in flood mitigation strategies. Few existing numerical models consider how vegetation affects dam breaks. This is because it is difficult to calculate vegetation drag force in unsteady rapidly varied flows. This study addresses this gap by developing a non-hydrostatic depth-integrated model to simulate the effect of rigid emergent vegetation on dam break flows under various flow conditions. The model was validated with experimental data. Vegetation was simulated with wooden cylinders with different coverage areas and densities within a straight channel. Three dam break scenarios were investigated in the experiment using different Froude numbers to represent diverse flow regimes. The non-hydrostatic depth-integrated model of the General Bottom Velocity method (GBVC4- DWL) was developed to incorporate the vegetation effect through the drag force equation for non-uniform open channel flows. The results show that rigid emergent vegetation significantly reduces wave celerity and height, particularly downstream, demonstrating its importance in flood mitigation. The numerical model accurately predicted wave behaviour outside the vegetation zone but have difficulties within it, highlighting the need for the model to be improved to capture complex vegetation-flow interactions.