Agenda of Floodplain Risk Management Advisory Committee

Reports submitted to the Floodplain Risk Management Advisory Committee to be held on Thursday 17 April 2025.

Floodplain Risk Management Advisory Committee AGENDA AND BUSINESS PAPER

Thursday 17 April 2025

ORDER OF BUSINESS:

CLAUSE PRECIS PAGE

ACKNOWLEDGEMENT OF COUNTRY 2

APOLOGIES 2

Confirmation of Minutes

CM-1 FLOODPLAIN RISK MANAGEMENT ADVISORY COMMITTEE MINUTES - 7 NOVEMBER 2024 2

DECLARATIONS OF INTEREST 2

Reports from Staff

RP-1 ELECT A CHAIRPERSON AND DEPUTY CHAIRPERSON 3

RP-2 2025 MEETING SCHEDULE 6

RP-3 2021-22-FM-0032 - Uranquinty Levee Upgrade - Investigation and Design 8

RP-4 2021-22-FM-0039 - Lake Albert Flood Mitigation Options - Feasibility Study 12

RP-5 2023 FMP 0073 Early Warning System Model Development 17

RP-6 2021-22-FM-0024 - Glenfield Drain and Flowerdale Storage Flood Mitigation Works 18

RP-7 2022-FMP-0103 Humula and Mangoplah Flood Studies 20

RP-8 17866- Levee System Upgrade - North Wagga 22

RP-9 Flood Project Implementation Status 25

RP-10 Reconnecting River Country Program 48

QUESTIONS WITH NOTICE 51

ACKNOWLEDGEMENT OF COUNTRY

APOLOGIES

Confirmation of Minutes

CM-1 FLOODPLAIN RISK MANAGEMENT ADVISORY COMMITTEE MINUTES - 7 NOVEMBER 2024

Rcommendation

That the Minutes of the proceedings of the Floodplain Risk Management Advisory Committee Meeting held on 8 August 2024 be confirmed as a true and accurate record, noting Council’s adoption of these minutes at its meeting 7 November 2024.

Attachments

1 ⇩.

Floodplain Risk Management Advisory Committee Meeting Minutes - 7 November 2024

DECLARATIONS OF INTEREST

Report submitted to the Floodplain Risk Management Advisory Committee on Thursday 17 April 2025. RP-1

Reports from Staff

RP-1 ELECT A CHAIRPERSON AND DEPUTY CHAIRPERSON

Author: Warren Faulkner

Analysis:

As this is the first meeting of the newly formed Floodplain Risk Management Advisory Committee, a Chairperson and Deputy Chairperson for the Committee must be elected.

Recommendation

That the Committee elect a Chairperson and Deputy Chairperson for the Term of the Committee.

Report

In accordance with the Floodplain Risk Management Advisory Committee Terms of Reference, the Committee shall elect a Chairperson and Deputy Chairperson.

9. Chairperson and Deputy Chairperson

(1) The Committee shall, at its first meeting following appointment, elect one of its voting members appointed under Clause 5 to be Chairperson of the Committee and one of its voting members appointed under the same clause to be Deputy Chairperson.

A staff member may be appointed as Chair with no voting powers.

(2) The Deputy Chairperson shall act in the absence of the Chairperson.

The Committee’s voting members are as follows:

Mayor, Councillor Dallas Tout	Council Elected Member
Councillor Jenny McKinnon	Council Elected Member
Councillor Lindsay Tanner	Council Elected Member
Austin Morris	Community Member
Michael Friend	Community Member
Patricia Murray	Community Member
Roslyn Pragnell	Community Member

There are no legislative requirements as to the process for electing a Chairperson or Deputy Chairperson of a Committee of Council. Accordingly, the election may take the form of a show of hands or secret ballot.

Committee members are requested to decide which form the election will take and proceed with the election of a Chairperson and Deputy Chairperson.

Financial Implications

N/A

Policy

Floodplain Risk Management Advisory Committee Meeting – Terms of Reference.

Link to Strategic Plan

Community Leadership and Collaboration

Objective: We have strong leadership

Outcome: We are accountable and transparent

Risk Management Issues for Council

No specific issues identified.

Internal / External Consultation

N/A

Report submitted to the Floodplain Risk Management Advisory Committee on Thursday 17 April 2025. RP-2

RP-2 2025 MEETING SCHEDULE

Author: Warren Faulkner

Analysis:

The Floodplain Risk Management Advisory Committee Terms of Reference require the Committee is to meet quarterly, as determined by the Committee.

Recommendation

That the Committee endorse the schedule of meeting dates for the next 12 months as outlined in the Report.

Report

A forward plan of meeting dates is agreed by the Committee each year. The following schedule of meeting dates is proposed for the remainder of the 2025 calendar year for the Committee’s consideration and endorsement:

· Thursday 17 April 2025

· Thursday 3 July 2025

· Thursday 18 September 2025

· Thursday 4 December 2025

Meetings are proposed to commence at 8:30am in the Council Meeting Room.

Extraordinary meetings and additional workshops may be held from time to time to discuss specific projects and items as required.

Financial Implications

N/A

Policy

N/A

Link to Strategic Plan

Community Leadership and Collaboration

Objective: We have strong leadership

Outcome: We are accountable and transparent

Risk Management Issues for Council

No specific issues identified.

Internal / External Consultation

N/A

Report submitted to the Floodplain Risk Management Advisory Committee on Thursday 17 April 2025

RP-3

RP-3 2021-22-FM-0032 - Uranquinty Levee Upgrade - Investigation and Design

Author: Andrew Mason

Director: Warren Faulkner

Summary:

The project is progressing as per the required program. The 50% design has been completed and a design report provided to Council for review.

Recommendation

That the Floodplain Risk Management Advisory Committee receive and note the update provided in relation to the Uranquinty Levee Upgrade Project.

Report

Royal Haskoning DHV (RHDHV) have completed the 50% design and provided it to Council for Review. Council provided the design and design report to DCCEEW and PWD for further review and passed the feedback onto RHDHV.

Council is progressing an alternative alignment of the eastern levee adjacent to Connorton Street so that it protects land that is zoned RU5 to allow for village expansion. The revised levee alignment has the potential to produce approximately an extra 50 1/4 acre blocks.

RHDHV has provided an estimate to complete the analysis as extra work and if the cost to protect the land proves viable and appropriate mitigation can be put in place, Council will need to finance this variation to the design from internal sources.

RHDHV have provided the attached update.

Andrew Morris from RHDHV will provide a presentation on the status of the current design and overall project.

Financial Implications

Policy and Legislation

N/A

Link to Strategic Plan

Safe and Healthy Community

Objective: Our community feel safe

Be responsive to emergencies

Risk Management Issues for Council

N/A

Internal / External Consultation

N/AN/A

Attachments

1 ⇩.

Uranquinty Levee Upgrade - Progress Report No. 5

Report submitted to the Floodplain Risk Management Advisory Committee on Thursday 17 April 2025

RP-4

RP-4 2021-22-FM-0039 - Lake Albert Flood Mitigation Options - Feasibility Study

Author: Andrew Mason

Director: Warren Faulkner

Summary:

Work on this project has commenced and Stantec are working on the project in line with the program.

Recommendation

That the Floodplain Risk Management Advisory Committee receive and note the update provided in relation to the Lake Albert Flood Mitigation Project.

Report

Update provided from Stantec:

Lake Albert Enhanced Flow Scheme - Feasibility Study

Part 3 - Mitigation Options Assessment - Summary

Stantec has been engaged by Wagga Wagga City Council to assess in further detail the feasibility of diverting additional flooding flows from Stringybark Creek and Crooked Creek and using Lake Albert to provide additional flood mitigation to the broader area, referred to as the ‘Lake Albert Enhanced Flow Scheme’.

This was first proposed as a flood mitigation option in the Wagga Wagga Major Overland Flow Floodplain Risk Management Study and Plan (MOFFRMS&P, WMA Water, 2021). The project has been divided into the following three stage sites:

· Stage 1 (LA01) Lake Albert Outlet Modification

· Stage 2 (LA02) Crooked Creek Modification

· Stage 3 (LA03 Stringybark Creek Modification

This report summarises the outcomes of findings of Part 1 Data Collection and Validation and Part 2 Investigative Works & Environmental Assessment. This report also summarises the outcomes of Phase 1 of Part 3 of the study, relating to identification and qualitative assessment of mitigation options.

The option assessment process involved:

· Identification of twelve key issues relating to the feasibility of any flood mitigation works as part of the Lake Albert Enhanced Flow Scheme. The identified key issues are:

a) Flood mitigation downstream

b) Limiting any adverse flood impacts

c) Limiting cultural heritage / environmental / ecological impacts

d) No significant increases to geotechnical risk

e) Achieving cost-effectiveness for capital costs and maintenance costs

f) Compatibility with other nearby Council projects

g) Minimising utility impacts

h) Containing works within Council-owned land

i) Limiting social disruptions to the community

j) Aesthetics and visual amenity

k) Community support

l) Providing improved amenity and addressing any maintenance issues.

· Identification of opportunities and constraints for each individual site of the Scheme. The opportunities and constraints have been identified through review of available data and site investigations, site visit observations, discussions with Council stakeholders, consultation discussions with representatives of affected recreation clubs.

· A review of the FRMS&P option for the three stages of the project concluded that based on key issues, opportunities and constraints, the options as proposed in the MOFFRMS&P were not seen as the most feasible solutions. Therefore, other preliminary options were considered using a qualitative assessment. Options have been grouped based not only on the stage of the project, but also the specific component. The components are as follows:

a) Stage 1 – Levee / Berm Around Lake

b) Stage 1 – Lake Outlets

c) Stage 2 – Channel Modification and Raised Footpath Berm

d) Stage 3 – Channel Modification

e) Stage 3 – Flood Mitigation for Recreation Clubs

· For those options seen as potentially feasible from the above qualitative assessment, preliminary modelling of these options (for the 1% AEP event and Lake Albert model only) has been conducted to confirm flood mitigation outcomes of each option.

Following the preliminary option identification and assessment process, Stantec in consultation with Wagga Wagga City Council has selected the following option to proceed to preliminary design, costing, modelling, and damage benefits assessment:

· Stage 1 – Lake Albert Outlet Modification:

a) Levee / berm around the lake is proposed to be both a sheet pile levee for sections and an earth embankment for other sections. The levee is proposed to be contained within the open space reserve between the lake and Lakeshore Drive and Lake Albert Road (where the original FRMS&P option was proposed to be road raising).

Due to the space limitations for the east side of the lake, sheet piles are the only feasible option at this location. For all other areas where open space with no existing trees is sufficiently wide, an earth embankment should be applied due to the greater cost effectiveness and enhanced visual amenity.

To be confirmed during preliminary design, however based on Council recommendations no freeboard will be applied above the 1% AEP level for the sheet pile sections of levee, and a 0.3m freeboard will be applied above the 1% AEP level for the earth embankment sections.

b) The revised lake outlet is proposed to be a two-stage weir for both the north and east outlets, with a low flow weir at both locations to allow the lake to drain to normal operating levels post-flood, and a high flow weir to convey additional flows during rarer flood events.

· Stage 2 – Crooked Creek Diversion Modification: After extensive consideration of key issues and opportunities and (critically) constraints of the Crooked Creek site, including preliminary modelling of several selected options, it was concluded that there were no feasible options for the Crooked Creek diversion modification.

Central to this outcome was the key issue of ecological and environmental impacts channel widening would have on the threatened ecological community (TEC) located along the creek, with any widening requiring the removal of large numbers of native trees. Furthermore, due to the Main St bridge invert being fixed downstream there was no opportunity for channel lowering or re-grading as there was insufficient fall across the channel length to facilitate channel invert lowering.

Finally, modelling showed that any footpath raising to the north to act as an additional berm was not feasible without resulting in adverse impacts for residential properties to the south of the diversion channel. Therefore, for the preferred option, it is proposed that no modification be made to the Crooked Creek diversion, and that it remains as per existing conditions.

· Stage 3 – Stringybark Creek Diversion Modification:

a) The channel modification is proposed to involve lowering of the channel invert to increase capacity, rather than channel widening as was proposed in the FRMS&P option. The extent of channel lowering will be from the outlet of the existing pond near Springvale Drive through Plumpton Road and further downstream, transitioning back to existing grade before the drop structure on the downstream end.

This channel modification provides additional capacity to limit the amount of local flooding for residential areas (the channel modification extends further upstream than the FRMS&P option which started at Plumpton Road). The maximum depth of channel lowering is proposed to be 2 metres.

The existing Plumpton Road twin culverts (2 x 1.8m) are proposed to be upsized to twin 2.4m W x 2.4m H culverts to reduce flooding over the road. This upgrade will align with the objectives of the Plumpton Road widening project.

No road raising is required for Plumpton Road and the Boat Club access driveway (unlike the FRMS&P option), as these works were not considered feasible and the increased channel capacity upstream of Plumpton Road negates the need for this road raising work.

b) At the downstream end of Stringybark Creek, the existing large culverts are proposed for replacement and lowering to increase the capacity of the channel, and to reduce the velocity of flows to reduce scour risk for the culvert headwall. In addition, a raising of the footpath on the north side of the culvert inlet is proposed to ensure that there is no overtopping of the channel in all events up to and including the 1% AEP.

This will improve the flooding risk for the sheds of the recreation clubs in the south-west side of Lake Albert. Current modelling (and observations from the 2012 floods) confirm these sheds are affected by high velocity, high hazard flows from the channel overtopping in rare flood events, with this flooding removed as part of the preferred option.

However, flooding of the sheds and the Boat Club building is proposed to worsen from lake flooding due to increased flood levels in the lake. To address this, flood risk consideration is to be given to permanent flood barriers around the sheds / buildings, combined with actuated flood barriers (self-raising barriers) for openings of the sheds / building.

Following this report, Council and the Flood Risk Management Advisory Committee (FRMAC) will confirm the selection of the preferred design to progress to preliminary design. Stantec will then conduct the following assessment of the final preferred option to be summarised in the Draft Feasibility Study report for the Lake Albert Enhanced Flow Scheme:

· Preliminary design of the preferred option.

· Flood Modelling: The updated TUFLOW models will be run for up to five design flood events; the 20%, 10%, 5%, 1% AEP and PMF events and results will be analysed to assess the impacts of the option on flooding. The post-mitigation flows from the Lake Albert will be modelled in the East model as well to simulate impacts of the preferred option. Only the critical duration for each of the five events will be modelled.

· High-level cost estimation will be prepared for the preferred option.

· Flood damage benefits assessment will be conducted using TUFLOW model results for the five design flood events to calculate Average Annual Damage (AAD) and Net Present Value (NPV) of flood damage benefits over the design life of the preferred option.

The draft Feasibility Study report will be placed on public exhibition, with workshops planned for directly affected stakeholders, with a post-exhibition final report to be issued incorporating comments from the FRMAC, Council and the community.

Stantec have provided the attached reports and will be providing a presentation to the committee.

Financial Implications

N/A

Policy and Legislation

N/A

Link to Strategic Plan

Safe and Healthy Community

Objective: Our community feel safe

Be responsive to emergencies

Risk Management Issues for Council

N/A

Internal / External Consultation

N/A

Attachments

Lake Albert Feasibility Study - Part 3 Report - Provided under separate cover

Report submitted to the Floodplain Risk Management Advisory Committee on Thursday 17 April 2025

RP-5

RP-5 2023 FMP 0073 Early Warning System Model Development

Author: Andrew Mason

Director: Warren Faulkner

Summary:

This Report provides an outline of the Early Warning System Model Development 2023 FMP 0073.

Recommendation

That the Floodplain Risk Management Advisory Committee receive and note the report regarding the Early Warning and Flood Prediction Project.

Report

This project is a development of a recommendation from the 2018 FRMSP.

An initial project was completed by Stantec and this has been developed into a specific and targeted approach to improve accessibility to flood and river data for the Council, the State Emergency Service and the public. The approach is to enhance and improve existing Council systems and work collaboratively with the SES and Bureau of Meteorology to improve access to data across the Local Government Area and the wider catchment.

Cameron Druery from Worley will be providing a presentation about the status of the project.

Financial Implications

N/A

Policy and Legislation

N/A

Link to Strategic Plan

Safe and Healthy Community

Objective: Our community feel safe

Monitor and enforce public safety

Risk Management Issues for Council

N/A

Internal / External Consultation

N/A

Report submitted to the Floodplain Risk Management Advisory Committee on Thursday 17 April 2025

RP-6

RP-6 2021-22-FM-0024 - Glenfield Drain and Flowerdale Storage Flood Mitigation Works

Author: Andrew Mason

Director: Warren Faulkner

Summary:

Lyall and Associates have been engaged to undertake further investigation into suggested mitigation options to reduce impacts in the Glenfield Drain catchment as identified in the Wagga Wagga Major Overland Flow Floodplain Risk Management Study and Plan (MOFFS).

Recommendation

That the Floodplain Risk Management Advisory Committee receive and note the update provided in relation to the Glenfield Drain and Flowerdale Storage Area Flood Mitigation Works Project.

Report

A comprehensive progress report on the work undertaken to date to make the MOFFS model for the Glenfield Road drain catchment fit-for-purpose to undertake a detailed assessment of the performance of the existing detention basins within the catchment is attached.

A copy of the model outputs for the Glenfield Road Catchment is provide as a separate attachment to the report.

Lyall & Associates met with Council officers on Wednesday 2 April 2025 to discuss the current performance of each detention basin in the catchment and identify which ones should be pursued to optimise their performance, thus ensuring that downstream impacts in major storm events are minimised.

Lyall and Associates are on track to complete this engagement in August 2025.

An employee of Lyall & Associates will present on a selection of model outputs to the Committee.

Financial Implications

N/A

Policy and Legislation

N/A

Link to Strategic Plan

Safe and Healthy Community

Objective: Our community feel safe

Be responsive to emergencies

Risk Management Issues for Council

N/A

Internal / External Consultation

N/A

Attachments

1.	Glenfield Road Drain Progress Report No. 1 - Provided under separate cover
2 .	Model outputs for the Glenfield Road Catchment - Provided under separate cover

Report submitted to the Floodplain Risk Management Advisory Committee on Thursday 17 April 2025

RP-7

RP-7 2022-FMP-0103 Humula and Mangoplah Flood Studies

Author: Andrew Mason

Director: Warren Faulkner

Summary:

WMAWater have commenced the study for Humula and Mangoplah and have conducted initial community consultation in the villages.

Recommendation

That the Floodplain Risk Management Advisory Committee receive and note the update provided in relation to the Humula and Mangoplah Flood Studies Project.

Report

Council engaged WMAWater in late September 2023, to undertake the Humula and Mangoplah Flood Study.

The relevant LiDAR data has been provided to WMAWater for development of the flood models.

WMAWater have built hydrologic models for both towns and have a hydraulic model for Mangoplah. Calibration for Mangoplah has commenced. The hydraulic build for Humula is ongoing.

Community Consultation was conducted at Humula on the 4 September 2024 and Mangoplah on the 5 September 2024.

WMAWater will be presenting to the committee regarding the status of this project.

Financial Implications

N/A

Policy and Legislation

N/A

Link to Strategic Plan

Safe and Healthy Community

Objective: Our community feel safe

Be responsive to emergencies

Risk Management Issues for Council

N/A

Internal / External Consultation

N/A

Report submitted to the Floodplain Risk Management Advisory Committee on Thursday 17 April 2025

RP-8

RP-8 17866- Levee System Upgrade - North Wagga

Author: Andrew Mason

Director: Warren Faulkner

Summary:

This project to upgrade the levee has commenced with preliminary tasks completed and further funding sources being investigated.

Recommendation

That the Floodplain Risk Management Advisory Committee receive and note the update to the Levee System Upgrade – North Wagga.

Report

A new project specifically about the implementation of the levee raising and third-party mitigation options has commenced.

The Project Sponsor is the Director Infrastructure Services.

An updated indicative timeline for the implementation of the raised levee and third-party mitigation options is provided below.

Stage	Duration	Commencement
Topographic Survey	6 months	August 2024
Environmental Assessment	4 months	November 2024
Floodgate Pipe Relining	4 months	April 2025
Civil Design including mitigation options for residents adversely affected by the levee raising	6-12 months	July 2025
Levee contractor procurement	4 months	July 2026
Levee construction	24 months	November 2027

For the North Wagga levee, Council currently has a funding pool of:

· $6.3M in SRV funding

· $1.1M in the original Commonwealth Development Grant to be expended by December 2025.

The CDG will be utilised to fund the floodgate pipe relining and the detailed design of the levee.

There is a shortfall of approximately $5M for the construction of the levee and with the need to provide mitigation to the 25 buildings adversely affected by the levee raising, there is potentially the need to raise a further $3.75M on top of the $5M.

Council has applied for funding through Round 3 of the Disaster Ready Fund to finance the shortfall for this project. Council should be notified later this year if it has been successful.

The status of the project is:

· The detailed survey for the levee design has been completed.

· The Review of Environmental Factors is well underway, a draft has been received and final comments have been provided back to the consultant. The final REF should be received shortly.

· Procurement is underway for the detailed design of the levee, this closed yesterday 16^th April, Council is aiming to have a design consultant appointed to the project by the middle of June.

· Procurement is underway for the relining of the existing 14 floodgates in the levee, preliminary access and environmental work has already been completed for this component of the project.

· A project steering committee will be engaged shortly to oversee this complex project.

Financial Implications

N/A

Policy and Legislation

Local Government Act

Development Control Plan 2010

Flood Risk Management Manual

Link to Strategic Plan

Safe and Healthy Community

Objective: Our community feel safe

Be responsive to emergencies

Risk Management Issues for Council

N/A

Internal / External Consultation

N/A

Report submitted to the Floodplain Risk Management Advisory Committee on Thursday 17 April 2025

RP-10

RP-10 Reconnecting River Country Program

Author: Andrew Mason

Director: Warren Faulkner

Summary:

Reconnecting River Country Program

Recommendation

That the Floodplain Risk Management Advisory Committee receive and note the update provided in relation to the Reconnecting River Country Program being carried out by DCCEEW.

Report

A report was presented to the FRMAC at its 8 August 2024 meeting that provided an overview of the Reconnecting River Country Program.

The program is in development. No flows have been delivered under the program and no decision has been made to select a flow option. No higher environmental flows will be delivered before December 2026.

The program is funded to prepare a Murrumbidgee Final Business Case by February 2025. This will recommend a flow option for delivery. The Final Business Case must be considered before proceeding to delivery.

In July 2024, funding was announced to upgrade a 1.5km section of Mundowy Lane to be resilient to flows up to 45 GL/day.

Council staff have been meeting regularly with DCCEEW and the design consultant, Jacobs, to work through design issues and to satisfy the needs of all concerned parties.

Financial Implications

N/A

Policy and Legislation

N/A

Link to Strategic Plan

Safe and Healthy Community

Objective: Our community feel safe

Be responsive to emergencies

Risk Management Issues for Council

N/A

Internal / External Consultation

N/A