Raise and / or release ?
by Greg Martin
To spill or raise – that ’ s the question ! The Hawkesbury recently suffered its third major rain event in 18 months .
While riverside communities stoically clean up and try to remain prepared for future floods , they are up against legislation they have little chance of changing . As The Hills mayor Peter Gangemi told Lower Portland residents at a meeting attended by his fellow councillors and others from the Hawkesbury City Council - “ This is the best part of The Hills ”.
More than 100 residents gathered to listen to Cr Gangemi and other councillors and they didn ’ t need convincing - what they wanted were answers .
An earlier meeting in August convened by Darren Osmotherly at his Paradise Cafe at Lower Portland was designed to provide answers as to how to protect properties from further flooding .
While Warragamba Dam is a water storage dam rather than a flood mitigation facility , those living close to the Hawkesbury River realise they risk threats of further flooding .
What they wanted to know at the hastily convened meeting was whether the legislation could be changed to allow for increased spillage from the dam which
Damage to ( the aptly named ) River Road , Lower Portland , after the March 2022 flood .
might offer them greater protection prior to imminent rain events .
But according to Water NSW , releasing volumes of water large enough to provide meaningful benefits ahead of a forecast flood “ could cause significant flooding downstream , as well as reduce evacuation time and increase the risk to life as roads could be cut ”. While the dam is currently 100 per cent full , according to a spokesman for Water NSW “ but it has been drawing down for the last couple of weeks ”.
But as a legislated water storage facility , it needs to be kept at 97 per cent . And
while it continues to rain in the catchment area , it will continue to be topped up .
Many in the room were initially sceptical of the other option , raising the dam wall .
A height of 14 metres has already been accepted by both the Hills Shire Council and Hawkesbury City Council .
Hawkesbury councillor Les Sheather said his council had resolved to support the raising of the dam wall .
“ It ’ s not going to stop flooding , but it will minimise flooding ,” he said .
As Chair of the Hawkesbury / Nepean Flood Mitigation Action Committee , Cr Sheather said there had been 156 floods in the Hawkesbury since European settlement .
“ We live on a floodplain so we ’ re going
Blocked creek and sluice gates at Lower Portland do little to improve drainage of properties during and after flooding .
to get flooding , but we can minimise that ( by the raising of the dam wall ),” he said . Those who attended the meeting were in no doubt that raising the dam wall would take time they just don ’ t have .
But there appears to be little likelihood of changing legislation that might protect those in flood prone areas .
According to Water NSW , “ Greater Sydney ’ s water supply is currently at its sustainable limit . As Warragamba Dam stores around 80 per cent of total supply , releasing stored water from the dam ... could represent a significant risk to [ Sydney ’ s ] water security .”
State Member for Hawkesbury Robyn Preston understands the urgent need for a change to the legislation .
“ It ’ s my responsibility to look after 70,000 people below Warragamba Dam ,” she said . “ People want action now . “ It ’ s a water catchment dam at the moment and I will meet with the decision makers and ask them to lower the dam ( water level ) now .”
On August 16 , Ms Preston attended a briefing with Premier Dominic Perrottet to talk about the findings of the independent
flood inquiry which is about to be released to the public .
Earlier in the month , Ms Preston delivered a Notice of Motion to the NSW Parliament in support of lowering the current water level of the Warragamba Dam and supporting raising the dam wall : Mr Speaker , I give notice that tomorrow I shall move that this House :
1 . Acknowledges the significant challenges that the Hawkesbury community has faced in the last two years as a consequence of repeated flood events .
2 . Calls on the NSW Government to amend legislation to allow for larger volumes of water to be released from Warragamba Dam to enhance flood mitigation .
3 . Recognises that without this change in this legislation , the dam operations without a higher wall will have little impact on flood mitigation .
4 . Raising the Warragamba Dam wall will be the most effective way to reducing the number and severity of floods that impact the Hawkesbury- Nepean Valley .
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THE HAWKESBURY INDEPENDENT theindependentmagazine . com . au ISSUE 148 // SEPTEMBER 2022 5