A flood similar to that which occurred in some Queensland catchments in 2001, would inundate 14,000 homes above floor level and destroy 6,500 homes in the Hawkesbury Nepean Valley (HNV).
At risk would be 43,000 residents and 9,000 employees of local businesses and the impact of such a disaster would be felt across the NSW and Australian economy and impact negatively on people and businesses outside the HNV.
It could cause $4.3 billion in direct damages and an estimated $8 billion in total tangible damages in the vicinity, according to NSW Infrastructure NSW’s 20-year infrastructure strategy
The strategy found that the western railway line would be disrupted for up to six months affecting coal and other freight exports from Central and Western NSW.
Floods would disrupt 6,000 daily train commuters from the Blue Mountains and passenger services from Central and Western NSW.
“Infrastructure NSW has been made aware of approximately 8000 residential lots and 60 hectares of commercial and industrial land that have not been developed due to evacuation constraints,” the report said.
Developments in the planning phase in which flooding would be a significant constraint include Penrith Panthers redevelopment, Riverstone West industrial development, Schofields precinct development and the Marsden Park development.
These developments include more than 8500 residential lots and over 150 hectares of commercial and industrial land.
Infrastructure NSW recommended the NSW government review all major flood mitigation options available, including rasing the Warragamaba Dam wall by 23 metres to significantly reduce the potential economic and social impact of flooding in the HNV.
“If major flood mitigation is not provided, roads in the HNV should be upgraded to ensure people can evacuate,” the report said.
The strategy estimated the cost for upgrading roads to allow people in the HNV to safely evacuate was, at least, $400 million to $600 million notwithstanding an increase in population. .
