Numerical modelling of non-cohesive embankment breach with the dual-mesh approach

Abstract

The numerical model BASEMENT, based on the two-dimensional shallow-water equations, is applied to breaching processes of non-cohesive earth embankments due to overtopping. The governing equations are solved using an explicit finite-volume method combined with a Godunov-type approach. For spatial discretization, a mass-conserving dual-mesh approach with separate, unstructured meshes for hydrodynamic and sediment computations is developed allowing for accurate terrain representation. The surface erosion is modelled with the Exner and sorting equations for multiple grain classes in combination with empirical bed-load transport formulas and advection–diffusion equations for suspended-load transport. Additionally, the lateral breach widening caused by gravitationally-induced slope failures is considered using a novel algorithm adapted for unstructured grids. The model is successfully applied to two recent laboratory experiments including plane and spatial dike breaches, and a field-scale embankment breach. Detailed comparisons between measured and simulated laboratory spatial breach formations confirm the basic model assumptions.

Keywords:

• Dual-mesh
• embankment breach
• overtopping
• sediment transport
• shallow-water equation
• slope failure

Acknowledgements

The free software BASEMENT (www.basement.ethz.ch) was developed with financial support of the Swiss Federal Office for the Environment (FOEN). The first author thanks the Competence Center Environment & Sustainability (CCES) of the ETH Domain for funding research on simulations of embankment failures.