The bell toll rings. Shame the government, how dare they make the new Windsor Bridge not flood proof. It will inevitably be next weeks new political football but before then, I went looking through the documents of the new Windsor Bridge of the final determination of the height and the final decisions on flood proofing for the new bridge.
Firstly the background, the new Windsor Bridge was constructed and completed in 2020 as the replacement of the previous heritage listed bridge, completed in 1931. The decision for the then Roads and Maritime Services to replace the bridge was based on the following findings; to increase traffic capacity and the deteriorating of the piers. RMS also promoted that the new bridge would have better flood immunity than the existing bridge.
“A new bridge would cope with higher levels of flooding and have the same flood immunity as surrounding approach roads on the northern bank.“
What can we achieve with a new bridge? – Transport for NSW (2016)
That is to say, the new bridge did have its opposition with locals opposing the demolition of the old bridge based on the heritage status with the rest of Windsor. Political members were divided on the replacement bridge with NSW Labor on the opposition side of the replacement bridge including leader Jodi McKay and Federal member for Macquarie, Susan Templeman. The local opposition petition also attracting up to 10,000 users.
“I didn’t entirely agree with those who thought of this project as a rape of Windsor’s heritage”
Liberal councillor Nathan Zamprogno (2020)
So looking back at the reports for the Windsor Bridge replacement project. The issues of flood immunity answers were addressed in one section the 2013 Submissions Report based on the original Environmental Impact Statement of 2012 (and previous reports in 2011). Under Issue 2.11, Flood immunity of project, some key points and comprises were made.
First, the bridge design was lowered as a response to visual amenity, according to RMS that there was “no benefit in providing a bridge that had a substantially higher flood immunity than Wilberforce Road and/or Freemans Reach Road.”. The new bridge as designed would be higher that the former heritage bridge but only “around the one in three year flood level” (the previous bridge was one in two years flood level).
The Submissions Report also noted on what determines a flood event with limitations on the “accuracy of the flood modelling process” and that “the exact flood immunity of the project in terms of recurring flood events has not been calculated as it would require modelling of a large range of flood events to produce a flooding frequency that would change over time.”. Overall it was determined that using historic flood data that the number of closures of the new bridge would be reduced from “three instead of eight” based on the new bridge’s increased height.
The Submissions Report also noted issues with potential flooding impacts of the river in general. The then Office of Environment and Heritage noted the “potential increases in flood levels are of concern, especially in the five year ARI flood event and for those additional properties affected by over-floor flooding.”. RMS ruled out having both the new and heritage bridge as they feared it would worsen any flooding impacts and that the old bridge “could damage or collapse during a large flood.”
“The current 1 in 100 AEP flood level at Windsor would be reached more frequently with a 9.1 per cent rainfall increase under climate change – becoming a 1 in 65 AEP event. Sea level rise impacts on the 1 in 100 AEP are largely confined to the lower reaches of the river.”
Hawkesbury-Nepean Valley Regional Flood Study Final Report Volume 1 for Infrastructure NSW by WMA Water (2019)
According to Hawkesbury Councillor Danielle Wheeler of the NSW Greens, there was another option of providing a separate river crossing that would be be higher than both the previous Windsor Bridge and current Richmond Bridge but no decision was made. The gazette proposed this bridge as being designed for a “a one in 100 year level bridge”.
“We need not a raised dam but more stringent development controls there, better evacuation routes and a more flood-educated population.“
Chas Keys – Former deputy director-general of the NSW State Emergency Service to the SMH (2019)
In 2013, former Transport reporter for the Sydney Morning Heard Jacob Saulwick wrote about the risks of major flooding in Western Sydney with the NSW Government looking at flood mitigation options for the Hawkesbury Nepean which was published in 2017. As of last week, the NSW Government is still working on flood modelling and the plan to raise Warragamba Dam, a proposal first drafted since the 1980s with also opposition by the people of Windsor.
@kypros1992 
You must be logged in to post a comment.