Narellan Creek Overland Flood Study (Vol 1) - Flipbook - Page 78
Narellan Creek Catchment
Flood Study
drainage infrastructure. In all cases the flood levels are not predicted to change by more
than 0.02 metres. Therefore, any uncertainty in the representation of structure losses does
not have a significant influence on the model results.
6.3.3
Blockage
As discussed in Section 5.3.2, blockage factors were applied to all culverts and bridges as
part of the design flood simulations. However, as it is not known which structures will be
subject to what percentage of blockage during any particular flood, additional TUFLOW
simulations were completed to determine the impact that alternate blockage scenarios
would have on flood behaviour. Specifically, additional simulations were undertaken by
adopting the 8low9 blockage scenario (normally adopted for frequent flood events >5% AEP),
and the 8high9 blockage scenario (normally adopted for rare flood events
