Narellan Creek Overland Flood Study (Vol 1) - Flipbook - Page 99
ITEM
Downstream
boundary
conditions
REVIEW OBSERVATIONS
The downstream boundary is modelled as a HT
boundary.
COMMENTS/
RECOMMENDATIONS
The HT relationship is a static water level at 65.5 mAHD for the 5yr
event.
FLOWPATH OBSTRUCTIONS AND CONSTRICTIONS
Buildings
Buildings have been represented through increase
roughness in the materials. This is based on the
cadastre 6 types defined:
o
Residential – moderate density
o
Residential – low density
o
Commercial – shopping centre
o
Commercial – high density
o
Industrial – moderate density
o
Industrial – high density
The roughness Manning9s n values are represented as a lot-based
average roughness. Delineation of building footprints is
recommended to reflect obstruction to overland flow afforded by
buildings.
MODEL PARAMETERS
Roughness
(Manning9s 8n9)
values
assigned in 2d
material layers
Land use polygons are used to define the material types
in the TUFLOW model
44 roughness (Manning9s n) values are assigned within
the 2D domain based on land use.
Land use types were delineated based on LEP zones or lot scale.
Detailed remote sensing is recommended for a detailed overland
flood analysis.
Material delineation is sufficient along some of the channels (e.g.,
sections of Narellan Creek near Harington Park). It might be
appropriate to retain the material polygons covering these areas
and utilise remote sensing for the urbanised areas.
CHECKS, WARNINGS AND ERRORS
Outputs in the
_messages
layer
The _messages layer was checked for the 1% AEP
simulation.
There are a number of warnings or checks. However, there are
none that would influence the model results.
