Morphological modeling is a complex task and the most advanced morphological model in the world is MIKE 21C. The model is very similar to MIKE 21, but operates on a curvilinear grid, and it is a parallel code able to utilize multiple cores, which is essential for the computationally very demanding studies for which the model is often applied. In addition to the hydrodynamic model, MIKE 21C calculates (helical) secondary flow from standard theory, including weak adaptation in space. Up to 16 sediment fractions can be specified, including cohesive sediment, and sediment transport formulas for bed-load and suspended load can be adjusted for each fraction in a generic manner. Bed-load is calculated with inclusion of the effect of the bed slope and helical flow, while suspended load is calculated from advection-dispersion equations for each of the fractions with inclusion of the secondary flow in the depth-integrated equations. MIKE 21C also includes an N-layer substrate model, which allows tracking the substrate dynamically in addition to the bathymetry. Other features include lateral erosion processes, including updating of the grid during simulations to account for bank erosion and updating of the bed roughness to account for bed forms.
The animation shows the time-varying bathymetry in a morphological simulation with MIKE 21C. The initial bathymetry shows the “Modeling the World of Water” image, while the final bathymetry shows the DHI logo. A 1-layer model was then applied with an initial substrate layer thickness equal to the difference between the initial and final bathymetry. The model has a width of 5 km, a depth of 2 m, a discharge of 12,000 m3/s and zero sediment inflow. Uniform sediment was applied with a grain size of 0.2 mm, and both bed-load and suspended load were calculated. It takes about 6 months to clear the sediment (on average about 1 m layer thickness) out of the model.
MIKE 21C has been applied for many studies around the world, including Jamuna Bridge, Chaktomuk Junction, Loire, Snake River.