High resolution airborne laser data provide new ways to explore the
role of topographic complexity in hydraulic modelling parameterisation,
taking into account the scale-dependency between roughness and
topography. In this paper, a complex topography from LiDAR is processed
using a spatially and temporally distributed method at a fine
resolution. The surface topographic parameterisation considers the
sub-grid LiDAR data points above and below a reference DEM, hereafter
named as topographic content. A method for roughness parameterisation
is developed based on the topographic content included in the
topographic DEM. Five subscale parameterisation schemes are generated
(topographic contents at 0, +/- 5, +/- 10, +/- 25 and +/- 50 cm) and
roughness values are calculated using an equation based on the mixing
layer theory (Katul et al., 2002), resulting in a co-varied
relationship between roughness height and topographic content.
Variations in simulated flow across spatial subscales show that the sub
grid-scale behaviour of the 2-D model is not well-reflected in the
topographic content of the DEM and that subscale parameterisation must
be modelled through a spatially distributed roughness parameterisation.
Variations in flow predictions are related to variations in the
roughness parameter. Flow depth-derived results do not change
systematically with variation in roughness height or topographic
content but they respond to their interaction. Finally, subscale
parameterisation modifies primarily the spatial structure (level of
organisation) of simulated 2-D flow linearly with the additional
complexity of subscale parameterisation.