Numerical modelling of flood inundation over large and complex
floodplains often requires mesh resolutions coarser than the structural
features (e. g. buildings) that are known to influence the inundation
process. Recent research has shown that this mismatch is not well
represented by conventional roughness treatments, but that finer-scale
features can be represented through porosity-based subgrid-scale
treatments. This paper develops this work by testing the interactions
between feature representation, subgrid-scale resolution and mesh
resolution. It uses as the basis for this testing a 2D diffusion-based
flood inundation model which is applied to a 2004 flood event in a
topologically complex upland floodplain in northern England. This study
formulated simulations with different grid mesh resolution and subgrid
mesh ratio. The sensitivity of the model to mesh resolution and
roughness specification was investigated. Model validation and
verification suggest that the subgrid treatment with higher subgrid mesh
ratio can give much improved predictions of flood propagation, in
particular, in terms of the predicted water depth. This study also
highlighted the limitation of using at-a-point in time inundation extent
for validation of flood models of this type. Copyright (C) 2010 John
Wiley & Sons, Ltd.