Friction decoupling and loss of rotational invariance in 2D flooding models

Comparison of two modelling strategies for 2D large-scale flood simulations

“…Faster arrival times in a LISFLOOD-FP simulation (with the localinertial approximation) than in a fully SWE simulation are also reported by Neal et al (2012b) for a dam-break case. This fact was related to the adoption of decoupled equations in the x-and ydirection (which leads to the creation of preferential flow pathways along the diagonal, as discussed by Neal et al, 2012b, and more recently by Cozzolino et al, 2021), to numerical diffusion, and, to a lesser extent, to the wetting and drying treatment. When the resolution is coarsened, both models provide arrival times that are quite similar to those obtained with the high-resolution mesh up to 12 h, whereas larger differences can be observed between the results of high-and low-resolution simulations in the 24-48 h time interval.…”