Brown Hill Creek Dam — Timeline Report 2011 - 2018

Contents

• Executive summary
• Timeline
• 22 March 2011 — Council considers flood mitigation options
• 4 October 2011 (period leading to consultation) — Draft Stormwater Management Plan and consultation materials
• 25 October 2011 — Councillor questions on dam effectiveness
• 22 November 2011 — Letter opposing the dam received
• 31 January 2012 — First major petition against the dam
• 28 August 2012 — Stormwater Management Plan endorsed
• February–March 2013 — SMP approved and gazetted
• May 2013 — Brochure mailed to residents
• 26 November 2013 — Background report on Part B progress
• 11 March 2014 — Second, larger petition and update report
• 23 September 2014 — Part B Report completed and options revised
• Late 2013–March 2014 — Early community engagement on Part B
• April 2015 — Council resolves to consult on Part B Report
• 13 May – 23 June/23 July 2015 — Formal consultation period
• 19 May 2015 — SMA Notice to prepare revised SMP
• 25 August 2015 — Consultation findings received by Council
• 22 September 2015 — Council selects Option D ("no dam") as final Part B solution
• 20 October 2015 — Audit Committee report on project status
• 27 October 2015 — Financial statements note on the project
• 9 February 2016 — Engagement report update
• 15–17 March 2016 — Final SMP submitted to the SMA
• April 2016 — SMA defers decision
• 28 June 2016 — Item 7.7 background and community implications report
• 2015–16 Annual Report — Project status summary
• 27 February 2018 — Regional subsidiary established
• 2017–18 Annual Report — Completed and planned works listed
• Key findings
• Open questions

Executive summary

This report traces, in strict chronological order, the public record concerning proposals to build a flood mitigation dam on Brown Hill Creek (upper Brown Hill Creek, within the Brown Hill Keswick Creek catchment) and the wider Stormwater Management Plan (SMP) process of which it formed part. The record begins in March 2011, when the City of Mitcham first considered flood mitigation options for Brown Hill and Minna Creeks [1], and continues through a 2011 draft plan proposing a 12-metre dam in Brown Hill Creek Recreation Park [1][2], sustained community opposition expressed through two large petitions [5][7][8], a formal "Part B" investigation process mandated by the Stormwater Management Authority (SMA) [6][10], and culminates in the five catchment councils' 2015 resolution to adopt a "no dam" Creek Capacity Upgrade option (Option D) [14]. The report then follows the plan's consolidation, submission to the SMA, and the eventual 2018 establishment of a regional subsidiary — the Brown Hill and Keswick Creeks Stormwater Board — to implement the agreed, dam-free works [21][22].

Across this period, the record shows evolving flood-risk estimates (from roughly 5,000 to nearly 7,000, then down to about 2,000 affected properties, reflecting revised hydrology and modelling) [1][2][10], recurring community consultation exercises [2][11][13], and formal governance steps by the five catchment councils — Adelaide, Burnside, Mitcham, Unley and West Torrens — working under SMA oversight [6][14][19].

Timeline

22 March 2011 — Council considers flood mitigation options

An item report to Council noted that the City of Mitcham is prone to flooding from Brown Hill and Minna Creeks, and that consultants had produced detailed inundation mapping and damage estimates for the first time since 1984 [1]. The report estimated approximately 5,000 properties would be affected by a 1:100 Annual Exceedance Probability (AEP) flood event, with likely damage of around $200 million if no action were taken [1]. A range of structural measures (including dams and weirs) and non-structural measures were under consideration [1]. The report discussed the possibility that the Brown Hill Creek Flood Control development could be declared a "Major Project" under the Development Act 1993, given potential impacts on four EPBC Act-listed endangered species and on Aboriginal and European heritage sites in the catchment [1].

4 October 2011 (period leading to consultation) — Draft Stormwater Management Plan and consultation materials

A draft consultation survey and newspaper advertisement text were prepared for the "Brown Hill and Keswick Creek Draft Stormwater Management Plan," seeking feedback on flood protection proposals including a "flood mitigation dam at Brown Hill Creek Recreation Park," detention basins at Glenside, the South Parklands and Ridge Park Reserve (Myrtle Bank), bypass and diversion culverts, and channel upgrades [2]. The advertisement stated that nearly 7,000 properties across the catchment were at risk of flooding, with potential damages of up to $180 million [2]. Consultation was scheduled between 31 October and 12 December 2011, including open days in Unley, Mitcham and Hilton [2].

25 October 2011 — Councillor questions on dam effectiveness

At the Council meeting, Cr Weaver asked what impact the proposed 12m flood mitigation dam at "site 1" (Brown Hill Creek Recreation Park) would have on the approximately 7,000 properties estimated to be affected under a 1-in-100 ARI event, and specifically on the 1,712 properties forecast to suffer over-floor flooding [3]. The answer, sourced from the Project Director via consultant WorleyParsons, stated that separate floodplain mapping isolating the dam's effect had not been prepared and would take about a month to produce [3]. A council-by-council table was provided showing that, if the SMP's full recommended strategy (including the dam) were implemented, Mitcham's flood-affected properties would fall from a baseline of 105 (33 over-floor, 72 under-floor) to 56 (19 over-floor, 37 under-floor), with WorleyParsons indicating a further reduction to about 35–45 properties was plausible after detailed design [3]. Total catchment-wide affected properties under the base case were given as 6,921, reducing to 1,321 under the recommended option [3].

22 November 2011 — Letter opposing the dam received

At the Council meeting (Item 19.1), Cr Weaver moved that a letter from Ms Barbara Hardy AO, dated 3 November 2011 and addressed to the President of Friends of Brownhill Creek, regarding the proposed dam in Brown Hill Creek Recreation Park, be received; this was seconded by Cr Munro and carried [4].

31 January 2012 — First major petition against the dam

Council received a petition (Item 5.1), signed by in excess of 5,000 signatories, stating: "We the undersigned, hereby PETITION Council to protect the environment and heritage of Brownhill Creek by opposing the damming of the creek" [5]. The petition related to the "Draft Brown Hill and Keswick Creeks Stormwater Management Plan" dated 26 August 2011, which recommended a 12m high flood mitigation dam in the Brown Hill Creek Recreation Reserve [5]. Mr Bellchambers, who provided a covering letter, was recorded as making a deputation to Council on the issue [5]. The recommendation before Council was that the petition be received [5].

28 August 2012 — Stormwater Management Plan endorsed

Council, together with the other four catchment councils (Adelaide, Burnside, Unley and West Torrens), endorsed the Stormwater Management Plan (SMP) for the Brown Hill Keswick Creek Stormwater Project [10][19]. The endorsed plan committed the five councils to an agreed group of structural works (Part A), and to further investigation of alternatives to structural works in upper Brown Hill Creek (Part B), specifically options that preferably excluded a flood control dam [10].

February–March 2013 — SMP approved and gazetted

The SMP was approved by the Stormwater Management Authority (SMA) in February 2013 and gazetted on 5 March 2013 [6]. The SMP identified Part A Works (about 80% of project value, addressing urban sub-catchments of Glen Osmond, Parklands and Keswick Creeks) and Part B Works (upper Brown Hill Creek options still to be finalised) [6]. The SMP confirmed the councils' committed preference for a "no dam" solution for Part B, with determination required within 12 months of gazettal [6]. Part B options listed included a Malcolm Street bypass in conjunction with a dam, two no-dam extended bypass options (3 and 3A), limited creek capacity upgrading, and a flood detention dam in the rural part of Brown Hill Creek [6].

May 2013 — Brochure mailed to residents

A brochure outlining the scope of Part A and Part B works was mailed to over 3,000 addresses in Unley, focusing mainly on the stormwater high-flow bypass culverts under consideration in the Part B process [6].

26 November 2013 — Background report on Part B progress

An item report described how, following detailed information from Part B investigations, attention was being given to the scope and cost of upgrading critical sections of Brown Hill Creek, noting that increasing creek flow capacity might be a full or partial alternative to the detention dam and/or bypass culverts [6].

11 March 2014 — Second, larger petition and update report

Council received a petition (Item 6.1) containing 10,083 signatures expressing opposition to any proposed flood mitigation dam(s) in Brown Hill Creek or its tributaries [7]. The motion to receive the petition, moved by Cr Weaver and seconded by Cr Fisher, was carried unanimously [8]. At the same meeting, an update report on the Brown Hill Creek Draft Stormwater Management Plan (Item 9.3) was moved by Cr Fisher, seconded by Cr Adcock, and the report was received for information only, carried [9].

23 September 2014 — Part B Report completed and options revised

A background report noted that under SMA order, the five councils had 12 months to finalise Part B works, and that the Brown Hill Keswick Creek Project Steering Group had reviewed options using revised 2013 Bureau of Meteorology hydrology data, updated hydraulic modelling, and revised cost estimates [10]. The revised data reduced peak 100-year flows by up to 26% in parts of upper Brown Hill Creek and decreased the estimated catchment-wide properties impacted by a 1-in-100-year flood from over 6,000 (per the 2012 SMP) to approximately 2,000, of which about 1,200 would experience above-floor flooding [10]. This reduction made the previously dismissed "Creek Capacity Upgrade" option newly feasible [10]. Eight options for managing upper Brown Hill Creek stormwater flows were investigated and summarised in the report [10]. The "Brown Hill Keswick Creek SMP Part B Report" was released to the public on 9 September 2014 [17][19].

Late 2013–March 2014 — Early community engagement on Part B

Community engagement on Part B commenced in late 2013 through meetings with community special interest groups, expanding to meetings with creek owners from March 2014 [13].

April 2015 — Council resolves to consult on Part B Report

Council resolved to carry out community consultation on the Part B Report [13].

13 May – 23 June/23 July 2015 — Formal consultation period

The formal consultation period on the Part B Report is recorded as running from 13 May until 23 June 2015 in some sources [13][17][18][19], while another source records the consultation as concluding on 23 July 2015 [11]. Open days were held in Unley on 18 and 24 May 2015 and in Mitcham on 28 and 30 May 2015 [13]. A total of 818 feedback forms were received: 88 from creek property owners (out of 216 distributed), 730 from members of the public (out of 1,074 issued), plus 76 written submissions [13]. Support for Option D varied: among creek owners, 42 of 88 respondents supported Option D, 42 opposed it, and 3 were unsure; owners of properties where only rehabilitation works were proposed showed higher support (68%) than owners facing capacity upgrade works (31%) [13].

19 May 2015 — SMA Notice to prepare revised SMP

The Stormwater Management Authority issued a Notice, pursuant to Clause 14(1) of Schedule 1A of the Local Government Act 1999, requiring the Cities of Adelaide, Burnside, Unley, Mitcham and West Torrens to prepare a revised Stormwater Management Plan for the Brown Hill Keswick Creek catchment by 30 September 2015 [14][19].

25 August 2015 — Consultation findings received by Council

Council received, for information and discussion, the report "Consultation findings on the Brown Hill Keswick Creek Stormwater Project: Part B Report" (dated variously as July or August 2015 across sources), publicly released on 13 August 2015 [11][13][18]. The consultation report noted that although effort was made to encourage creek owners to respond, only about 40% of creek property owners did so, compared with only 4% of non-owner occupiers [11].

22 September 2015 — Council selects Option D ("no dam") as final Part B solution

Council resolved, on a motion by Cr Tilley seconded by Cr Taeuber, carried unanimously, to determine that Option D – Creek Capacity Upgrade is the recommended solution for Part B Works under the SMP 2012 [12][14]. The resolution recorded that Option D had the lowest capital, maintenance and whole-of-life costs, provided the required 100-year ARI flood protection (and higher protection for shorter storms), satisfied the councils' "no dam" preference, avoided suburban bypass culverts, preserved heritage/cultural sites, and remained within the SMP 2012 budget [14]. The Chief Executive Officer was delegated authority to prepare a revised SMP for submission to the SMA [14]. Council reaffirmed the tri-level government cost-sharing proposal from the 2012 SMP, and resolved that the project councils continue investigating a Regional Subsidiary as the delivery/management vehicle [14]. The resolution also provided contingencies: if government cost-sharing did not materialise, councils reserved the right to review project scope; and if the five councils could not agree on Option D, the CEO was authorised to ask the SMA to use its statutory powers to finalise and approve the SMP itself [14].

20 October 2015 — Audit Committee report on project status

An audit committee item recorded that the SMP required establishment of a regional subsidiary to undertake detailed design, construction and maintenance of Part A and B works, subject to Federal/State funding, and that the five councils had reached agreement on approximately 80% of works under Part A [15]. The forecast SMP cost was estimated at approximately $147 million over a 10-year implementation period, with Mitcham's 10% local government contribution equating to between $5.0 million and $7.5 million [15]. The report confirmed all five councils had formally resolved in September 2015 to accept Option D (the no-dam option), with the final SMP due for SMA submission in January 2016 [15]. It also recorded that Mitcham had paid $250,000 in February 2015 as its local government contribution toward the Goodwood Junction rail project's Brown Hill Creek diversion, subject to 50% SMA reimbursement [15].

27 October 2015 — Financial statements note on the project

Note 19 of the City of Mitcham's financial statements reiterated the SMP history: SMP 2012 gazetted March 2013; Part B determination extended by the SMA to September 2015 due to complexity and community interest in the "dam or no dam" question; the Part B Report completed September 2014; and all five councils' September 2015 resolution to accept Option D, with the final Plan due for SMA submission in January 2016 [16].

9 February 2016 — Engagement report update

An item report reiterated the Part B Report's public release on 9 September 2014, formal consultation running 13 May to 23 June 2015, presentation of consultation findings to catchment councils in August 2015, and confirmation that all five catchment councils had resolved to accept Option D (the "No Dam" option) [17].

15–17 March 2016 — Final SMP submitted to the SMA

The final SMP, consolidating Parts A and B (the "Brown Hill Keswick Creek Catchment Plan 2016"), was forwarded to the SMA for approval; one source dates this submission to 15 March 2016 [18], while other sources date it to 17 March 2016 [19][20][22], with a revised estimated project cost of $140 million [20][22].

April 2016 — SMA defers decision

At its April Board meeting, the SMA deferred a decision on the 2016 SMP until July 2016 [19].

28 June 2016 — Item 7.7 background and community implications report

A Council report (Item 7.7) recapped the project's history: the SMP 2012 endorsed by the five councils in August 2012, gazetted March 2013; the Ridge Park Detention Dam identified as part of agreed works, initially funded by the City of Unley pending reimbursement by other catchment councils; the SMA's 19 May 2015 Notice; consultation running 13 May to 23 July 2015 per this report; and the 22 September 2015 Council resolution endorsing Option D and delegating SMP finalisation to the CEO [18][19]. The report confirmed that, as of the date of writing, the SMA had not yet approved the final SMP [19]. It also noted that flood risk in the catchment "remains," although expenditure on the Ridge Park Dam would reduce (not eliminate) downstream flood risks [18].

2015–16 Annual Report — Project status summary

The City of Mitcham's 2015–16 Annual Report recorded that the SMP 2012 was gazetted by the SMA in March 2013, that Part B investigations took longer than planned (SMA extension to September 2015), that all five councils formally resolved in September 2015 to accept Option D, and that the final combined "Brown Hill Keswick Catchment Stormwater Management Plan 2016" was submitted to the SMA on 17 March 2016 with a revised estimated cost of $140 million, alongside continued work on establishing a Regional Subsidiary [20].

27 February 2018 — Regional subsidiary established

The South Australian Government gazetted the establishment of the Brown Hill and Keswick Creeks Stormwater Board, a regional subsidiary in which the City of Mitcham holds a 10% interest [21][22]. Council equity-accounted for its share of the subsidiary in the 2017/18 Annual Financial Statements [22].

2017–18 Annual Report — Completed and planned works listed

The Board's annual report listed infrastructure works for the "major implementation phase" (totalling an estimated $140 million), including South Park Lands detention basins ($17.4M), lower Brown Hill Creek capacity upgrade ($39.1M), flow diversions from Keswick Creek to lower Brown Hill Creek ($43.1M), upper Brown Hill Creek capacity upgrade and rehabilitation (part $30.8M combined), Glen Osmond Creek minor works ($0.8M), and gross pollutant traps ($1M) [21]. Completed works listed included the Ridge Park flood control dam ($2.8M) on Glen Osmond Creek, the Brown Hill Creek diversion culvert delivered by DPTI in 2013 as part of the Goodwood Junction railway upgrade ($5M, which superseded other proposed works), and a Mount Osmond interchange dam modification improving an existing flood detention dam built as part of the Adelaide Crafers Road upgrade [21]. The City of Mitcham's financial statements for 2017/18 repeated the project history, confirming the final "Brown Hill Keswick Catchment Stormwater Management Plan 2016" was submitted to the SMA on 17 March 2016 at an estimated $140 million, and that the Stormwater Board was gazetted on 27 February 2018 [22].

Key findings

• The originally proposed measure specific to Brown Hill Creek itself was a 12-metre flood mitigation dam in the Brown Hill Creek Recreation Park/Reserve, first documented in the 2011 draft Stormwater Management Plan [1][2][5].
• Estimated catchment-wide flood-affected property numbers varied across the record: approximately 5,000 properties in March 2011 [1], nearly 7,000 properties (with damages up to $180 million) in the October 2011 consultation materials [2], 6,921 in the October 2011 base-case modelling [3], and approximately 2,000 (about 1,200 above-floor) following revised 2013 hydrology data reported in September 2014 [10].
• Community opposition to a dam was expressed through at least two large petitions: one exceeding 5,000 signatures received 31 January 2012 [5], and a second with 10,083 signatures received 11 March 2014 [7][8]; a letter of opposition from Barbara Hardy AO was also received by Council on 22 November 2011 [4].
• The Stormwater Management Plan (SMP) 2012, endorsed by the five catchment councils on 28 August 2012 and gazetted by the SMA in March 2013, formally recorded the councils' preference for a "no dam" solution for Part B works in upper Brown Hill Creek [6][10][19].
• Following an SMA-mandated Part B investigation, revised hydrology data, and formal community consultation in 2015, all five catchment councils resolved (Mitcham on 22 September 2015) to adopt Option D — the Creek Capacity Upgrade, a "no dam" solution — as the final Part B works option [12][14].
• Consultation findings on Option D showed divided views among creek property owners (42 in favour, 42 against, out of 88 respondents) but a high level of support from the wider community [13].
• The consolidated Brown Hill Keswick Catchment Stormwater Management Plan 2016 (combining Parts A and B) was submitted to the SMA for approval in March 2016, with a revised estimated project cost of $140 million [18][19][20][22].
• Implementation of the agreed, dam-free scheme was subsequently vested in the Brown Hill and Keswick Creeks Stormwater Board, a regional subsidiary gazetted on 27 February 2018, in which the City of Mitcham holds a 10% interest [21][22].
• A separate, smaller flood control dam — the Ridge Park flood control dam ($2.8M) — was constructed on Glen Osmond Creek (not Brown Hill Creek) as part of Part A works and is listed among completed works [21].

Open questions

• The record gives conflicting dates for the end of the 2015 Part B community consultation period: 23 June 2015 in several sources [13][17][18][19] versus 23 July 2015 in another [11]; the record does not resolve which is correct.
• The record gives conflicting dates for the submission of the final 2016 Stormwater Management Plan to the SMA: 15 March 2016 in one source [18] versus 17 March 2016 in others [19][20][22].
• The record does not show the exact date or outcome of the SMA's eventual approval/gazettal of the final 2016 SMP; it shows only that a decision was deferred by the SMA Board in April 2016 pending a July 2016 review [19], and that the record as provided does not confirm when or whether that approval occurred.
• The record does not specify the formal title or date of any single plan or policy document that explicitly labels itself as incorporating "Option D as the final solution" after the 23 September 2014 Part B Report; the closest documented instances are the "Brown Hill Keswick Creek Catchment Plan 2016" [18] and the "Brown Hill Keswick Catchment Stormwater Management Plan 2016" [20][22].
• The petition figures cited across sources for the March 2014 petition differ slightly (10,083 in the agenda item [7] versus a reference to "10,087 signatures" in a previous answer not directly sourced to a numbered citation in this material) — the record here confirms 10,083 [7].
• The record does not detail the specific reasoning behind the SMA's April 2016 deferral of the 2016 SMP decision, beyond noting that a decision was deferred to July 2016 [19].