Infrastructure NSW has delivered its recommended 20 year State Infrastructure Strategy prepared by Molino Stewart to the NSW Government. Molino Stewart was commissioned to do the investigations because of our ongoing involvement in flood impact investigations in the Hawkesbury Nepean Valley since 1995. The Infrastructure NSW report sets out a preliminary investigation which draws heavily on previous work, particularly the 1995 Warragamba Flood Mitigation Dam EIS. That EIS was never placed on public exhibition because the incoming Labor Government decided that provision of flood mitigation capacity on top of Warragamba's water storage was not the most appropriate means of managing flood risks in the Hawkesbury Nepean Valley.
However, since the 1995 EIS was produced, significant development has occurred on the floodplain. The report found that in a repeat of the record 1867 event more than 7,000 homes would flood and more than 1,000 homes of those would experience significant structural damage. More than 50,000 people would need to evacuate. The preliminary investigation confirmed that a flood mitigation dam at Warragamba would significantly reduce flood risks in the Hawkesbury Nepean Valley and would be economically worthwhile.
The full Hawkesbury Nepean report and findings can be viewed here.