Environmental Engineering Reference
In-Depth Information
Fig. 13.19
The drainage system and the digital elevation model (DEM) of the study area. (See colour version of this
figure in Colour Plate section)
1Dmodel, and the same DEMwas used in the 1D/
2D modelling. There were 34 pathways and 22
ponds generated as the surface network, and 10
Multiple-Linking-Elements (MLEs) were used to
describe the discharge coefficient(s) at manholes
(Leandro et al. 2007). Seven weir equations were
used as linkages between the ponds andmanholes,
the ponds and ponds, or the ponds and pathways,
respectively.
An arbitrarily selected one-hour rainfall event
of 200-year return period with 52mm/h constant
intensity was applied to the study area, and the
outfall to the River Aire was represented as a free
outlet. The results simulated by the 1D/1D and
1D/2D models for flood extent are shown in
Figure 13.20. These figures highlight that the
major flood extents were similar for both model
outputs. The 1D/1D model produced a smaller
flood area but with a greater flood depth due to
the inundation being confined by the ponds. In the
case of the 2D representation more opportunity is
afforded for the overland flow to move over the
terrain and this leads to wider flood extents and
smaller average depths. However, a close exami-
nation of the results highlighted that, for the 2D
model, at some local points the flow flood depth
was greater than that predicted by the 1D model.
This again emphasizes the value of the 2D terrain
model in that within the 1D framework only the
average ground elevation is considered for each
grid cell.
This case study has highlighted that it is feasi-
ble to utilize the 1D/1D and 1D/2D modelling
approaches to predict flood extent; a much fuller
description of the application and calibration of
the models is given by Leandro et al. (2009).
UKWIR demonstration projects
The next phase of the FRMRC urban flood re-
search was to complete three UKWIR funded case
studies to trial the research software in an industry
environment. The intention of the studies was to
enhance and improve understanding of the way in
