Narellan Creek Overland Flood Study (Vol 1) - Flipbook - Page 8
Narellan Creek Catchment
Flood Study
During extreme floods (i.e., the PMF), nearly 1,400 road segments would be cut. This
includes more than 300 road segments inundated with more than 1 metre of water. This
would result in floodwater extending well beyond the road reserve in many areas resulting
in inundation of adjoining properties.
Depths or more than 1.5 metres are predicted around the Mount Annan Marketplace at the
peak PMF. Likewise, depths of well over 1 metre are predicted around the Narellan Town
Centre. This would likely place a significant number of staff and patrons at risk in these busy
commercial precincts.
A significant number of roads and properties in the lower catchment are also predicted to
be exposed to significant inundation depths, however, this is driven by elevated Nepean
River water levels rather than local catchment runoff.
A flood damages assessment was also completed to understand the potential financial
impact of flooding on the community. This determined that the average annual flood
damage cost is approximately $3 million. This reflects the approximate amount that would
need to be set aside each year to pay for replacing damaged stock and building contents and
indirect costs such as clean up and loss of trading. Therefore, the potential economic
impacts of flooding in the catchment can be significant.
The outcomes of the climate change simulations also showed that future increases in rainfall
have the potential to increase existing flood levels and depths by at least 0.1 metres across
most locations within the catchment. Therefore, climate change does have the potential to
increase the existing flood risk in the future.
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