Gowrie Creek Flood Mitigation Presentation - 26 February 2014

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Information about Gowrie Creek Flood Mitigation Presentation - 26 February 2014
Education

Published on March 6, 2014

Author: ToowoombaRC

Source: slideshare.net

Description

Slideshow presented during community consultation as a part of the Gowrie Creek Catchment Flood Mitigation project. Addresses specifically the planned works in East Creek. For more information view the project page at: http://www.toowoombaRC.qld.gov.au/EastCreek

Gowrie Creek Catchment Flood Mitigation (East Creek) 26 February 2014 Click to edit Master subtitle style

Overview • Background/ History • East Creek Master Plan & Options Analysis • Detention Basin Information • Consultation Strategy • Project Schedule

Gowrie Creek Management Strategy • Gowrie Creek Catchment Management Strategy was developed & adopted by Council in 1998 • Instigated by residents and business owners concerned about the state of the City’s waterways • Developed through extensive consultation & involvement from community, businesses & govt depts • A holistic approach to catchment management to address key issues such as land acquisition, flood mitigation, bank stabilisation, water quality, revegetation recreational use and aesthetics. • Work from Upstream to Downstream (Start in West Creek followed by East Creek down along Black Gully and eventually into Gowrie Creek) to maximise flood mitigation benefits in the CBD

West Creek works already completed • Murray Clewett Wetlands – 35ML detention basin • Spring to Stenner St Basins - 2 Detention Basins (27 ML and 28 ML) • Alderley St basin - 100ML detention basin • Wilf Gowlett Basin – 60ML detention basin • Clewley Park Wetland – an off-stream wetland used to treat baseflows. • Clewley Park Basin – completed 2013 • West Ck Channel (Herries – Russell) - Current • West Creek Channel & Goggs Street Stormwater upgrade – currently under construction • Dent Street Rail Bridge Upgrade – Current • Confluence (East & West Cks) – OCR project

2007 Flood Risk & Mapping Study • Undertaken by Council & Independent consultants • Identified specific properties at risk of flooding in standard design events • Confirmed and built upon the 1998 study findings • Made recommendations for further works including Garnet Lehmann and Ballin Drive Detention Basins.

2011 Flood Event Currently the best flood design practices call for a nominal Q100 event for flood immunity. The 2011 event •Estimated as a 1-in-300 year ARI rainfall event •1-in-500 year stream-flow due to wet catchment •The 2011 was far in excess of current design standards

Insurance Council of Australia Report “ The detention basins built along West Creek were overwhelmed; all were overtopped but none breached. It is expected that the capacities of these basins are too small to have exerted any meaningful mitigating effect on waterflows passing through them”. ICA Hydrology Panel, 14 February 2011 This comment was based on early observations immediately after the flood in assessing the structural integrity of the basin • The ICA report was an analysis of the available data immediately following the storm event including rainfall, meteorological data, stream flow and inundation data. • No hydrological or hydraulic modelling was presented by the ICA as part of this assessment. • Hydrological analysis and hydraulic modelling of the effect of the basins was then undertaken in conjunction with various experts as part of TRC’s submission to QFCI in April 2011.

2011 Flood Event QFCI Outcomes “At the time of the 10 January 2011 flood, approximately 2/3 of the programmed flood mitigation works for the Gowrie Creek system had been implemented. Had this not been the case, flooding and the consequences of flooding would have been significantly worse” Neil Collins – QFCI, Principal Hydraulic Engineer, expert witness Hydrological analysis used as basis for Qld Flood Commission of Inquiry (QFCI) submission showed: •A reduction of 30% flows in West Creek through the CBD for the 2011 event area due to the construction of detention basins.

NDRRA Category D Exceptional Circumstances Objective: fast tracking the completion of the flood mitigation strategy works (3 years vs 20+ years) Budget: $25M ($10M feds, $10M state, $5M TRC) Under NDRRA program construction works with the aim of being completed on ground by end 2014

Project Deliverables • Updated Hydraulic Model of the catchment • West Creek Channel at confluence (OCR Project) • West Creek Channel Upgrade (James – Herries St) • Goggs Street Stormwater Upgrade East • East Creek Master Plan • Ballin Drive Detention Basin • Garnet Lehmann Detention Basin • East Creek Channel Upgrade (James – Herries St) Creek Master Plan? Why detention basins?

Project Deliverables Spring & Ramsay Streets Detention Basin • Reconstruction of inlet works • Landscaping improvements to be developed in consultation with the local community Wilf Gowlett Detention Basin (West Creek) • Currently investigating improved landscaping options and upgrades to basin outlet to improve basin efficiency

Hydraulic Model Peer Review Panel  Dr Ian Brodie Senior Lecturer, Faculty of Engineering & Surveying University of Southern Queensland  Dr James Ball Associate Professor, Faculty of Engineering University of Technology Sydney  Dr Grant Witheridge Director, Catchments & Creeks Pty Ltd revision of Qld Urban Drainage Manual  Mr Grantley Smith Principal Engineer and Manager University of NSW Water Research Laboratory

East Creek Masterplan Project Purpose Masterplan Outcomes •Build upon earlier studies in the catchment. •Optimise flood mitigation benefit utilising the updated model •Prioritise all the mitigation works required in the catchment. •Additional works not able to be funded under NDRAA can be Prepared for incorporated into the 10yr CWP or alternatively, provides a basis for additional funding applications. Prepared for 13 Gowrie Creek Flood Risk & Management Study 19 February 2014

East Creek Masterplan Elements of the Masterplan The Masterplan considered the following mitigation measures: •Detention basins: o Review of basins from previous studies o Review of operation of existing minor basins o Potential new basin location external to creek channel •Channel improvement works •Road crossing upgrades Prepared for 14 Gowrie Creek Flood Risk & Management Study 19 February 2014

East Creek Masterplan Elements of the Masterplan Spring / Ramsay Detention Basins •Reconstruction of inlet works •Landscaping improvements to be developed in consultation with the local community Wilf Gowlett Detention Basin •Currently investigating improved landscaping options and upgrades to basin outlet to improve basin efficiency Prepared for 15 Gowrie Creek Flood Risk & Management Study 19 February 2014

East Creek Masterplan Detention Basin Option Assessment Detention Basin Locations •Build upon earlier studies into basin locations •Preferred basin locations are in Garnet Lehmann Park and Ballin Drive (Amanda Drive Park) •Central location in catchment and best areas available for Prepared for construction Prepared for 16 Gowrie Creek Flood Risk & Management Study 19 February 2014

East Creek Masterplan Detention Basin Option Assessment Review of options for Garnet Lehmann & Ballin Drive Basins Option Configuration Total Volume Concept Estimate 1 $5.9M Single Basin at Ballin Dr (includes Stenner St.) 42ML $5.6M 3 Single Basins at Garnet Lehmann and Ballin Dr (includes Stenner St.) 117ML $11.5M 4 Two basins at Garnet Lehman (includes Alderley St.) 158ML $16.9M 5 Three basins at Ballin Dr (includes Stenner St.) 105ML $12.8M 6 17 75ML 2 Prepared for Single Basin at Garnet Lehmann Multiple Basins at Garnet Lehman and Ballin Dr. (includes Alderley St. and Stenner St.) 263ML $29.7M Gowrie Creek Flood Risk & Management Study 19 February 2014

East Creek Masterplan Preferred Basin Selection Nominal 100 Yr Flood Mitigated Properties (43 currently flooded ) Option Description 1 2 Single Basin at Garnett Lehman Single Basin at Ballin Dr (includes Stenner St.) Single Basins at Garnet Lehmann and Ballin Dr (includes Stenner St.) 3 4 5 6 Prepared for 18 Two basins at Garnet Lehmann (includes Alderley St.) Three basins at Ballin Dr (includes Stenner St.) Multiple Basins at Garnet Lehmann and Ballin Dr. for Prepared (includes Alderley St. and Stenner St.) Buildings Removed From Flood Extent 5 7 Road Crossings Trafficable 1 1 11 3 22 5 7 3 26 6 Gowrie Creek Flood Risk & Management Study 19 February 2014

East Creek Masterplan Preferred Basin Selection Reductions in peak discharges (Nominal 100-yr) at specific locations Flow Reductions at Specific Locations (Nominal 100-yr) Option Location James St. 90 m3/s % Reduction Ruthven St. 117 m3/s % Reduction 1 Single Basin at Garnet Lehmann 80 11% 105 10% 2 Single Basin at Ballin Dr 74 18% 104 11% 3 Single Basins at Garnet Lehmann and Ballin Dr 57 37% 84 28% 4 Two basins at Garnet Lehmann 47 48% 75 36% 5 Three basins at Ballin Dr 66 27% 97 17% 6 Multiple Basins at Garnet Lehmann and Ballin Dr. 44 51% 73 38% Prepared for 19 Gowrie Creek Flood Risk & Management Study 19 February 2014

East Creek Masterplan Preferred Basin Selection Selection Criteria for Basin Performance •Basin selection was made in consultation with Council Staff and considered the following: o Reduction of Flood Hazard o Mitigated Properties o Improved Road immunity o Social impacts on public spaces o Cost Benefit Prepared for Based upon these Criteria Option 3 was selected as the preferred option Prepared for 20 Gowrie Creek Flood Risk & Management Study 19 February 2014

East Creek Masterplan Flood Mitigation Outcomes Outcomes of the East Creek Masterplan o Peak flow reductions at specific locations Location Existing Conditions(m3/s) ECMP (m3/s) % Reduction Bridge Street 202 172 15% Ruthven Street 117 84 28% James Street 90 57 37% South Street 71 39 45% Mackenzie Street Upstream 39 23 39% Buildings at Risk of flooding o Flood Mitigated Properties Scenario 10yr 50yr 100yr Base Condition 19 38 43 ECMP 9 16 24 Total Mitigated 10 22 19 Prepared for Prepared for 21 Gowrie Creek Flood Risk & Management Study 19 February 2014

East Creek Masterplan Strategy Costs Strategy Costs of implementing Full ECMP Strategy Elements Concept Estimate 1 Detention Basins $11,5M 2 Channels (includes James St.) $8,6M 3 Road Crossings $24,5M Total Cost $44.6M Prepared for 22 Gowrie Creek Flood Risk & Management Study 19 February 2014

Why Detention Basins in East Creek? • 2 large basins provide better outcome than 4-5 smaller basins • Ballin Drive and Garnet Lehmann Park central location in catchment area available for construction • Reduction in peak flows at critical locations downstream James/Kitchener Street crossing Ruthven Street crossing • Significant reduction in depth and speed of floodwaters

Community Engagement What we’ve done to date: • Letters to adjacent homes and businesses • Media launch (8 Nov 2013) • Community information session (11 Nov 2013) • Focus group workshop (2 Dec 2013) • Revisions to the concept designs • Meeting of interest groups and individuals (Feb 2014)

Key Concerns ISSUE RESPONSE Loss of trees Minimum 2 for 1 replacement Garnet Lehmann 378 to approx 310 Ballin Drive 97 to 96 Impact on fauna and flora Design improves biodiversity Expert to undertake independent environmental assessment Dog walking Will remain an off-leash park Perceived loss of park space Park will always be a usable space Appearance of basins Natural in design Minimal concrete

Ballin Drive Concept November 2013

Ballin Drive Concept February 2014

Ballin Drive Playground Concept

Ballin Drive Concept Images

Ballin Drive Concept Images

Garnet Lehmann Concept- November 2013

Garnet Lehmann Concept – February 2014

Garnet Lehmann Preliminary Layout

Garnet Lehmann Preliminary Layout

Garnet Lehmann Preliminary Layout

Garnet Lehmann Preliminary Layout

Garnet Lehmann Preliminary Layout

Consultation Strategy Going Forward Drop-in Information Sessions • 1st & 2nd and 8th & 9th March 2014 • 10am – 2pm, The Green Hall, Rangeville State School • Review design plans, ask questions and provide feedback Community Workshops • 5th and 12th March • 6pm – 8pm South Toowoomba Bowls Club • Discussion on the detailed design • Review of tree palette and input into tree replanting

Consultation Strategy • Ongoing meetings with community groups and individuals • Flyer • TRC website update – Video and presentation – Frequently asked questions – Updated design information • Park signage, concept layouts

Speak to the project team We welcome your input •Attend information sessions and register for workshops • Website – www.toowoombarc.qld.gov.au/eastcreek • Email – info@toowoombaRC.qld.gov.au • Phone – 131 TRC

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