Why do we no longer need a dam in Brownhill Creek when every solution prior to 2012 required one?
Back in 2012 and before a dam was always seen as part of the answer. Every engineering solution included a dam, somewhere. It was politically unpopular in some quarters however having said that.
Now the Project says we do not need a dam to achieve the flooding protection desired. Many people against the dam are reminding us that all the engineering solutions do not require a dam.
Interestingly before the change of focus on a no dam solution ALL the engineering solutions included a dam. A complete turnaround.
We have moved from a continuous we must have a dam to an emphatic a dam is not necessary. What has caused this I ask?
Some time ago all 5 councils endorsed looking at no dam solutions. We did this in my opinion to ensure we have given due diligence by searching all possible options.
Within it seems days this had become in the public arena that the 5 councils had endorsed a “preferred no dam” policy. This soon became the ideology of the Project too, reinforcing the public expectation. And more recently of course the public consultation was based on the Project presenting (without Council approval I hasten to add) a preference for a no dam solution.
It is my opinion that the project have got caught up in the politics of the situation and became hell bent on providing the solution that they thought they were charged to find rather than find the right solution. Promoting one solution, particularly one that appears to be the politically expedient one, in a public consultation gives me cause to think this way.
So in an environment where experts are advising the intensity of rainfall in the hills face will be greater than when we needed a dam we now don’t need a dam.
I find it difficult therefore to believe that the solution does not include a dam as part of the solution.
I understand that all previous unencumbered independent expert reports recommended a dam be included for good reason. The Project could not be expected to produce an unbiased, independent report for the best and most effective solution when it has been instructed to report with very specific limiting instructions to not “prefer” any solution including a dam.
The promotion of the limited conclusion of The Project as the “preferred” option has contributed to the misconception by the community that Option D is “preferred” as the best option (of all the Options) by the Councils. Build a dam into the total solution as recommended by the independent experts.
Unfortunately Trevin what you call the ‘previous unencumbered independent expert reports’ were based on data that was out of date and contained errors. A lot of people new this at the time but unfortunately those ‘in charge’ weren’t willing to listen and amend their reports after spending hundreds of thousands of dollars on them.
If you study ‘all the reports’ you will find that Option D is the standout solution to mitigate the flooding risk in the wider catchment.
It’s a good thing that the Stormwater Managment Authority will look at this as it is apparent that Elected Members of one Council in particular can’t see the bigger picture and are only focused on what happens within their borders.
Thanks Mike. You are correct, in that there is one Council in particular which can’t seem to see the bigger picture on this issue and is only focused on what happens within one small area within their borders despite the direct impact on many of their own residents and residents of the neighbouring Council. Option B2 is obviously the best option as it meets all the criteria for flood mitigation, is outside the recreation Park and reduces to a minimum the amount of “rehabilitation” in suburban gardens in Mitcham and Unley. A dam is essential to provide some control over floodwaters from any future significant rain event, whether the rain at the time complies with the current data or the data applicable at the time of the event.
The standard effective solution to mitigate flooding is to build flood control dams and that is what numerous civil engineers have recommended as the best solution for Brown Hill Creek along with cleaning out the existing channel to restore some flow capacity through Mitcham, Unley and downstream. A flood control dam simply captures stormwater runoff and regulates its flow out of a pipe through the base of the wall to prevent flooding downstream.
The original proposed Dam site was on rural land Ellison’s Gully well away and out of sight from the Brown Hill Creek Recreation Park. That Dam was “provisionally approved” by the newly formed Stormwater Management Authority in 2008. There are maybe 10 homes on rural blocks within a kilometre of that site and only two Companies and one individual owner some of whose land would need to be acquired or have an inundation easement placed on it for the Dam.
Then the local resident and Mitcham Council “No Dam” pushback commenced in earnest. The SA Government stepped in and along with the five Councils involved in the project engaged Worley Parsons to come up with alternative sites for the dam and other Options. While indicating a Dam in Ellison’s Gully would solve the problem Worley Parsons duly proposed an alternative dam smack bang in the middle of the Recreation Park. Predictably all hell broke loose with vocal locals leading a spreading political agitation to have “The Dam” scrapped in favour of any other solution.
What was conveniently lost in all the ensuing confusion and furore is that ‘The Dam’ was never meant to be in the Recreation Park in the first place. It was deliberately moved there from Ellison’s Gully and for no apparent good reason. Siting it in the middle of the Recreation Park was bound to and duly did provoke massive indignation and strident opposition from a misinformed public.
Another equally unnecessary and highly provocative Option proposed by Worley Parsons was to build 3 kms of huge bypass culverts following the Creek under residential streets through Millswood and Unley Park. This was borderline lunacy dressed up as feasible engineering and again it duly provoked a public outcry. Thus the ‘No Dam’ die was cast.
Eventually a series of ‘public consultations’ were staged which unsurprisingly confirmed that the public would prefer Creek Widening to The Dam or Culverts. Figures were then produced to weigh up the comparative costs of the Options. The Dam (still just barely alive and now back in Ellison’s Gully after its public outrage driven eviction from the Recreation Park) had its construction cost estimate loaded with a crippling 40% contingency while the Creek Widening had only a 15% contingency added (which is now proving to have been vastly under estimated).
Equally strangely, the proposed Creek Widening and its cost estimates completely missed two critical sections totalling 600 metres in length with attendant land acquisition and intensive and expensive engineering through Millswood, some of the most desirable and expensive residential property in Adelaide.
How so many supposedly competent engineers responsible for the preparation and endorsement of that plan failed to see those costly missing critical sections of land acquisition and work beggars belief and demands explanation.
Many of those who should have detected and corrected these glaring flaws and omissions retain roles in Government agencies and our Councils. They should be identified and instructed to show cause given the serious consequences now being born by the public and our purse.
In late 2016, when it came down to which Option should be adopted for flood mitigation in Upper Brown Hill Creek members of the five Councils funding the works, Unley, Mitcham, Burnside, Adelaide, and West Torrens were told by their engineers that the Creek Widening would be around $5 million cheaper than the Dam. They were unaware that this advice was based on loaded costings and inexcusable omissions that favoured Creek Widening and which should have been challenged and corrected by their supposedly competent advisors before being placed before them for a decision. Predictably the majority decided for the supposedly cheapest option.
If correct cost estimates had been placed before the Councillors, we would now have a flood detention Dam in Ellisons Gully protecting the 5000 or so residents in Unley and Mitcham.
Instead, we have a dangerously ineffective and destructive Creek Widening scheme being rammed through the heart of Millswood destroying hundreds of trees and the riverine setting of adjoining homes and it simply does not work. The just completed section above Regent Street couldn’t even cope with what was likely a 1:20 ARI rain event from overnight thunderstorms in late November 2023. It broke its banks just before the Regent Street culvert and flooded across the road into adjoining properties and homes. It should now be patently obvious that Creek Widening is ineffective and that even a 1:50 let alone a 1:100 ARI rain event is inevitably going overwhelm it and cause a widespread flooding disaster across Unley.
A flood protection Dam in Ellisons Gully could have been finished five years ago. Instead, thousands of Unley residents are expected to wait 15 years longer until 2015 at the earliest for completion of Creek Widening which we can see already is a dangerously ineffective solution.
I hear now that the costs of the Creek widening have already doubled and the five Council’s Regional Subsidiary responsible for the works is paying former politician lobbyists to plead with the Commonwealth for more money, the same Commonwealth which the authors of the Brown Hill and Keswick Creek Flood Mitigation Plan misled by claiming Creek Widening would be less expensive than the Dam in the first place.
Scrapping the destructive, dangerously delayed and already visibly ineffective Creek Widening with its already outrageous cost blow outs and instead building the detention dam in Ellison’s Gully should be the next corrective step along with sidelining those responsible for this dangerous and costly debacle.