Two-dimensional hydraulic modelling of submerged river training structures

Abstract

River training structures, such as dikes and chevrons, are commonly used for improving riparian navigation conditions. These structures are usually submerged under most flows and are aligned at variable angles to the main river flow direction. In this study, two different approaches for two-dimensional hydraulic modelling of submerged dikes and chevrons in MIKE 21 Flow Model FM have been analysed: (i) by representing the geometry of the structures explicitly in the bathymetry of the river channel (i.e. bathymetry approach), and (ii) by utilising the “dike” sub-grid module, where the flow past a structure is calculated by employing an empirical discharge relationship (i.e. dike module approach). The model results have been compared to theoretical and empirical studies, as well as to field observations and measurements. The obtained results indicate that the bathymetry approach is the more appropriate method for simulating predominantly submerged river training structures. However, these types of models should be used only for general assessment of potential river engineering solutions. For more detailed analysis of solution options, more complex models are recommended, e.g. three-dimensional hydrodynamic models.