Consultation findings on the Brown Hill Keswick Creek Stormwater Project: Part B Report Appendices Report Prepared for the Brown Hill Keswick Creek Stormwater Project by: Natalie Fuller and Associates Pty Ltd in partnership with URPS JULY 2015 Contents 1. Appendix A: Consultation Materials 2. Appendix B: Copies of Advertisements 3. Appendix C: Information Sheet issued following consultation 4. Appendix D: Verbatim Comments from Creek Owners 5. Appendix E: Written Submissions Appendix A: Consultation Materials • Summary Brochure – Managing Stormwater Flows in Upper Brown Hill Creek • Fact Sheets > Creek Capacity Upgrade Works > Creek Rehabilitation Works > Legal Agreements • Letters to the following households: 1. Owners of properties traversed by upper Brown Hill Creek where creek capacity upgrade including creek rehabilitation works are proposed 2. Owners of properties traversed by upper Brown Hill Creek where creek rehabilitation works only are proposed 3. Owners of properties traversed by upper Brown Hill Creek where no creek capacity upgrade works are proposed due to the construction of the DPTI culvert between the railway corridor and Aroha Terrace, Forestville 4. Owners of properties traversed by upper Brown Hill Creek where no creek capacity upgrade or rehabilitation works are proposed upstream of Brownhill Creek Recreation Park 5. Non-owner occupiers of properties traversed by upper Brown Hill Creek 6. Interested members of the public from the City of Unley 7. Interested members of the public from the City of Mitcham 8. Interested members of the public from other places. 9. Follow up letter sent to recipients of letters 1-6 on 5 June 2015. • Feedback forms tailored to the recipients > A tan feedback form for recipients of letter 1 > A green feedback form for recipients of letter 2 > A purple feedback form for recipients of letters 3-6 > A blue feedback form for recipients of letters 7-9. MANAGING STORMWATER FLOWS IN UPPER BROWN HILL CREEK The Brown Hill Keswick Creek (BHKC) The 2012 SMP groups works into Part A This brochure focuses on Part B Works. It Stormwater Project is a collaborative and Part B. outlines the findings of the Part B Report effort between the catchment councils prepared by the BHKC Stormwater Part A Works: are designed to mitigate of Adelaide, Burnside, Mitcham, Unley Project on the investigations of eight flooding generated from the mainly urban and West Torrens to mitigate serious options to manage stormwater flows in sub-catchments in lower Brown Hill Creek flood risks and help safeguard properties the upper Brown Hill Creek catchment. and Keswick, Glen Osmond and Parklands across the catchment of Brown Hill and Creeks. These works, which comprise The report identifies Option D – Keswick Creeks. approximately 80% of the project, have ‘Creek Capacity Upgrade’ – as the In 2013, the Stormwater Management already commenced. preferred option. Authority (SMA) endorsed the 2012 Part B Works: are designed to provide Prior to making any final decisions, Stormwater Management Plan (SMP) for flood mitigation in the upper Brown Hill the councils will undertake a formal the Brown Hill Keswick Creek catchment. Creek catchment. community consultation process. Refer The main objective of the 2012 SMP is to to the back page for details. The 2012 SMP identifies a process to mitigate the risk and reduce the impact investigate and determine Part B based of major flooding on properties within on the councils’ preference to pursue the BHKC catchment, up to and including a feasible and whole of catchment a 100 year average recurrence interval community supported ‘no dam’ solution. (ARI) flood. A 100 year ARI flood is also referred to as a 1 in 100 year event, and has a 1% chance of occurring in any given year. CITY OF ADELAIDE CITY OF WEST TORRENS SOUTH ROAD SOUTH ROAD KESWICK CREEK PARKLANDS CREEK GREENHILL ROAD GREENHILL ROAD PORTRUSH ROAD ADELAIDE GLEN OSMOND CREEK AIRPORT GOODWOOD ROAD GOODW CITY OF UNLEY FULLARTON ROAD UNLEY ROAD CITY OF BURNSIDE ANZAC HIGHWAY CROSS ROAD BBROWN HILL CREEK RO W CITY OF MITCHAM N H IL L C RE EK OOD ROAD LEGEND Catchment boundary Upper Brown Hill Creek catchment Overview What are the characteristics of • The estimated number of properties How were the eight options upper Brown Hill Creek? impacted by a 100 year ARI flood determined and assessed? over the entire Brown Hill Keswick The Brown Hill Keswick Creek catchment Investigations commenced with the Creek catchment decreasing from comprises four watercourses of which original five options from the 2012 approximately 7,000 (2012 SMP) to Brown Hill Creek is the most significant, SMP – being dam based options A1 and just over 2,000 properties – of which particularly in terms of stormwater A2, and high flow bypass culvert options approximately 1,200 would experience flow conveyance. C1, C2 and C3. Three new options B1, above-floor flooding. B2 and D were developed in the Part B Upper Brown Hill Creek refers to the Due to the reduced level and extent investigation process. section of the creek upstream of Anzac of forecast flooding, a greater length of Highway to its source in the rural land of Options have been assessed based on the creek has the capacity to carry the the Mitcham hills. Peak flows and flooding level of flood protection, estimated costs, predicted flood flows. result from either short duration storms environmental impacts and community which produce the most flooding from feedback to 2014. the urban area of the catchment or longer What mitigation options All eight options provide approximately duration storms which produce most were considered? the same level of flood protection for flooding from the rural area. Eight options have been considered. As the 100 year ARI event. The number of summarised in the table (see right), the potential flood impacted properties along options differ in how they combine the What technical data has changed upper Brown Hill Creek (Mitcham and following three components: since the 2012 SMP? Unley Council areas) is reduced from over The Part B investigation process has 1. A detention dam (at one of two sites: 400 to about 25 properties, with none of benefited from: Brown Hill Creek Recreation Park or those 25 properties likely to experience Ellisons Gully) above floor flooding. • Revised hydrology (rainfall) data released in mid-2013 by the Bureau 2. High flow bypass culverts (laid However, initial work indicated that of Meteorology and updated runoff under suburban streets along the options involving high flow bypass culverts forecasts (hydrologic modelling) relevant route) (Options A1, A2, C1, C2 and C3) would • Upgraded hydraulic modelling and 3. Creek capacity upgrade works be too costly to implement. at critical sections of the creek floodplain mapping showing the extent For this reason, investigations have (including bridge upgrade works) of stormwater inundation beyond focused on Options B1, B2 and D. the watercourse In addition, all of the options include • Updated project cost estimates based undertaking creek rehabilitation works to on the revised technical information. rehabilitate the creek towards achieving ‘good condition’ in order to assist flow Applying revised data has significantly capacity along the full length of upper altered the flood risk profile with: Brown Hill Creek. • Peak flows reduced by up to 25% These components are described over in parts of the upper Brown Hill the page. Creek catchment 2 MANAGING STORMWATER FLOWS IN UPPER BROWN HILL CREEK Upgrade options SUMMARY OF FLOOD MITIGATION OPTIONS FOR UPPER BROWN HILL CREEK OPTION DETENTION DAM HIGH FLOW CREEK CAPACITY UPGRADE BYPASS CULVERT Site 1: Brown Hill Creek Anzac Highway to Leah Street; Cross Road A1 Malcolm Street to Victoria Street* Recreation Park to Hampton Street Anzac Highway to Leah Street; Cross Road A2 Site 2: Ellisons Gully Malcolm Street to Victoria Street* to Hampton Street Anzac Highway to Leah Street; sections Site 1: Brown Hill Creek B1 between Mitchell and Malcolm Streets; Recreation Park Cross Road to Hampton Street; Fife Avenue Anzac Highway to Leah Street; sections B2 Site 2: Ellisons Gully between Mitchell and Malcolm Streets; Cross Road to Hampton Street; Fife Avenue Hampton Street to Victoria Street Anzac Highway to Forestville Reserve; C1 via the railway corridor with sections upstream of Hampton Street Malcolm Street leg (Route 3A)* Hampton Street to Victoria Street Anzac Highway to Forestville Reserve; C2 via suburban streets (Route 3)* sections upstream of Hampton Street Anzac Highway to Forestville Reserve; Hampton Street to Victoria Street sections between Douglas and C3 via the railway corridor without Malcolm Streets; sections upstream Malcolm Street leg* of Hampton Street Anzac Highway to Forestville Reserve; Creek rehabilitation along the full length of upper Brown Hill Creek from Anzac Highway to Brown Hill Creek Caravan and Holiday Park sections between Victoria and Mitchell Streets; Orphanage Park; Douglas to D Malcolm Streets; Cross Road to Hampton Street; sections upstream of Hampton Street to Muggs Hill Road *As detailed in the Part B Report. Under all options, some public road bridges need to be upgraded to meet required flow capacity. ESTIMATED CAPITAL COSTS ($M) OPTIONS COMPONENT A1 A2 B1 B2 C1 C2 C3 D Dam 24.1 28.8 24.1 28.8 –––– High flow bypass culvert 19.2 19.2 –– 43.4 46.4 28.6 – Creek capacity upgrade works 4.4 4.4 6.3 5.4 10.0 10.0 11.0 17.0 Public bridge upgrades 0.9 0.9 1.6 1.6 2.8 2.8 4.0 8.5 Creek rehabilitation 2.9 2.9 2.7 2.7 2.5 2.5 2.3 1.8 Easements 0.4 0.4 1.2 0.6 1.2 1.2 1.4 3.2 BHC diversion by DPTI 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 ESTIMATED TOTAL COST 56.9 61.6 40.9 44.1 64.9 67.9 52.3 35.5 May 2015 3 Components of the eight options Detention dams at a location where the flow can be Importantly, it is not proposed to create A detention dam temporarily stores accommodated.