Agenda of Floodplain Risk Management Advisory Committee

Reports submitted to the Floodplain Risk Management Advisory Committee to be held on Thursday 8 August 2024.

Floodplain Risk Management Advisory Committee AGENDA AND BUSINESS PAPER

Thursday 8 August 2024

ORDER OF BUSINESS:

CLAUSE PRECIS PAGE

ACKNOWLEDGEMENT OF COUNTRY 2

APOLOGIES 2

Confirmation of Minutes

CM-1 FLOODPLAIN RISK MANAGEMENT ADVISORY COMMITTEE MINUTES - 15 MAY 2024 2

DECLARATIONS OF INTEREST 2

Reports from Staff

RP-1 Local & Regional Risk Reduction Stream - Levee Pump Augmentation 3

RP-2 2021-22-FM-0024 - Glenfield Drain and Flowerdale Storage Flood Mitigation Works 5

RP-3 2021-22-FM-0032 - Uranquinty Levee Upgrade - Investigation and Design 7

RP-4 2021-22-FM-0039 - Lake Albert Flood Mitigation Options - Feasibility Study 9

RP-5 2022-FMP-0103 Humula and Mangoplah Flood Studies 11

RP-6 Flood Project Implementation Status 12

RP-7 Reconnecting River Country Program 33

RP-8 Floodgate 15 A 37

QUESTIONS WITH NOTICE 41

ACKNOWLEDGEMENT OF COUNTRY

APOLOGIES

Confirmation of Minutes

CM-1 FLOODPLAIN RISK MANAGEMENT ADVISORY COMMITTEE MINUTES - 15 MAY 2024

Recommendation

That the Minutes of the proceedings of the Floodplain Risk Management Advisory Committee Meeting held on 24 May 2024 be confirmed as a true and accurate record, noting Council’s adoption of these minutes at its meeting xx xx 2024

Attachments

1 ⇩.

FRMAC Minutes - 15 May 2024

DECLARATIONS OF INTEREST

Report submitted to the Floodplain Risk Management Advisory Committee on Thursday 8 August 2024

RP-1

Reports from Staff

RP-1 Local & Regional Risk Reduction Stream - Levee Pump Augmentation

Author: Andrew Mason

Director: Warren Faulkner

Summary:

A consultant has been appointed for this project.

Recommendation

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

Report

Stantec have completed extensive analysis of the four floodgates and determined that floodgates 8 and 25 are a priority. They have been completing damage assessments across the two catchments to enable the determination of a BCR balanced across the risk appetite, time of inundation, capital cost of the pumps and required infrastructure, and perceived utilisation of the pumps under flood conditions.

Stantec have also been developing an inundation model for the area around gate 25 for when the Kooringal Rd Spillway comes into effect in a 0.20% AEP event.

Stantec will be presenting at this meeting.

Financial Implications

N/A

Policy and Legislation

N/A

Link to Strategic Plan

Community leadership and collaboration

Objective: Wagga Wagga has strong community leadership and a shared vision for the future

Plan long term for the future of Wagga Wagga

Risk Management Issues for Council

N/A

Internal / External Consultation

N/A

Report submitted to the Floodplain Risk Management Advisory Committee on Thursday 8 August 2024

RP-2

RP-2 2021-22-FM-0024 - Glenfield Drain and Flowerdale Storage Flood Mitigation Works

Author: Andrew Mason

Director: Warren Faulkner

Summary:

Lyall and Associates have provided an update on the project.

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

To ensure the MOFFS model is providing more reliable outputs and reflects more accurately overland flood behaviours, Lyall and associates recommended that the 2021 model provided to them be updated to:

· Reduce the cell size to 2.5 m (from 5 m) to more accurately define the capacity of the overland flow paths.

· Incorporate additional stormwater pits and pipes, particularly in the headwaters of the study area to ensure that the rate and volume of runoff that discharges to each detention basin is accurately represented.

· Update the location where the discharge hydrographs are injected into the TUFLOW model.

In addition to the above, Lyall & Associates also anticipated that it would be necessary to update the way buildings are represented in the model and the invert levels of the already modelled piped drainage system.

A variation to the contract was approved in February 2024 to update the model.

Lyall and Associates update for this report is:

“We have completed the bulk of the model development and are now in model testing phase.”

Lyall and Associates have advised that their program is currently running about a fortnight out of sync with the revised timeline submitted to the 15 February 2024 FRMAC meeting, however they should still be able to complete this project in July 2025.

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 8 August 2024

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 preliminary design has been completed.

Recommendation

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

Report

Royal Haskoning DHV (RHDHV) have completed the preliminary design and conducted their first round of community consultation in Uranquinty. The second round of community consultation is booked in for the 13 August 2024 at Uranquinty.

Council has asked RHDHV to change the alignment of the eastern levee so that it protects land that is zoned RU5 to allow for village expansion.

RHDHV will provide an estimate to complete this extra work and there will be a variation request put into the Department of Climate Change, Energy, the Environment and Water (DCCEEW) once this is received.

There is limited scope in the remaining grant allocation to cover this extra cost and so Council will have to cover some of this extra work from internal funds.

Proposed new alignment to protect more developable land.

Financial Implications

There may need to be a variation to the project budget for the change of scope requested for the eastern levee.

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

Report submitted to the Floodplain Risk Management Advisory Committee on Thursday 8 August 2024

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

From Stantec:

Completed tasks to date:

· Data review and FRMS&P model review, summarised in a Stage 1 report

· Initial environmental assessment summarised in a draft summary report

· Initial stakeholder consultation with directly affected organisations (boat club, sailing club, country club and dragon boat club) completed on 1 and 2 August, attended by Council and Stantec

Using feedback from these initial stakeholder discussions completed recently, we can proceed with initial review and update of preliminary design. Next steps include:

· Initial community consultation, to commence in the next several months, consultation materials have been drafted

· Preliminary design of combined option and updated flood modelling

· Site investigations including Geotech investigations and utilities assessment

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 8 August 2024

RP-5

RP-5 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 will be conducting some community consultation in the villages within the next couple of months

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 and they are planning to conduct community consultation towards the end of August in the two villages to calibrate the models against historical records and memories.

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 8 August 2024

RP-6

RP-6 Flood Project Implementation Status

Author: Andrew Mason

Director: Warren Faulkner

Summary:

This Report outlines the status of the flood projects across the various studies that Council currently has underway.

Recommendation

That the Floodplain Risk Management Advisory Committee receive and note the report in relation to Flood Project Implementation Status

Report

Council has over 60 recommendations from the three recently completed studies and is working its way through the studies. The spreadsheet tracking these projects is an attachment to this report.

With regard to RE3 from the 2018 FRMSP and RM04 from the 2021 MOFFS, Council staff will be presenting the current status and type of information available on the Council webpage with regard to flooding and a brief outline of the future direction for this page .

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

As outlined in the Report.

Internal / External Consultation

N/A

Attachments

1 ⇩.

Flood Projects Implementation Tracking Spreadsheet

Report submitted to the Floodplain Risk Management Advisory Committee on Thursday 8 August 2024

RP-7

RP-7 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

The Reconnecting River Country Program aims to increase the frequency and extent rivers connect to wetlands and floodplains, to improve the health of Country in the Murray and Murrumbidgee valleys and make the best use of water for the environment.

The program is proposing to remove constraints along environmental flow corridors to enable the flexible use of water for the environment. Removing these constraints is critical to achieving the Murray-Darling Basin’s Plan’s environmental outcomes.

An environmental flow corridor is the area of land to be inundated by environmental flows up to the selected flow option limit. This area of land includes the riverbank, wetlands and low-level floodplain areas which the program aims to inundate more frequently with environmental water to mimic the natural cycle of the river.

The environmental flow corridors would provide landholders with certainty on the maximum inundation extent from potential releases for environmental flow purposes. Mapping of the flow corridor, for each of the flow options being assessed, can be viewed using the program’s inundation mapping.

If the program proceeds to delivery, the environment, and private and public land, would see benefits from increased environmental flows. However, some properties and public areas may require assistance to manage the impacts of low-level overbank inundation.

As such, the program is consulting on the development of program measures to assist landholders, First Nations people and local government agencies to manage the impacts of proposed higher environmental flow releases. These measures may include works and actions to improve First Nations people’s connection and access to Country. We will continue to discuss program measures with stakeholders seeking feedback to inform the development of these measures.

The extent of work and inundation associated with the RRCP

A package of early works and other measures has been scoped for Mundowy Lane that will improve access during periods of higher river flows including higher environmental flow options being considered by the program. The detailed design for this project is currently out to tender and a consultant will be appointed shortly.

Mundowy Lane is an important arterial road crossing Beavers Creek and the Murrumbidgee River, near the township of Collingullie.

Due to the current height of the southern section of Mundowy Lane, between the Sturt Highway and Beavers Creek, flows of 35,000 ML/day (5.51m) at Wagga Wagga see water beginning to cross over the road reducing traffic to a single lane rather than two lanes. At 44,000 ML/day (6.44m) at Wagga Wagga, the road is closed causing detours of up to 50km for local traffic.

The program has identified the road as a barrier to delivery of higher environmental flows and is scoping a package of early works to raise its southern section. The road is owned, operated and maintained by Wagga Wagga City Council.

The program is considering raising the southern section of Mundowy Lane to a level that will prevent inundation during flows up to 45,000 ML/day at Wagga Wagga.

New culverts could be placed in the raised roadway allowing the passage of higher flows underneath and reducing the risk of damage to the road.

Mundowy Lane

https://rrcwebviewer.pages.dev/inundation_viewer_mbg

The other projects currently progressing within the Wagga LGA are:

· Beavers Island Rd

· A pedestrian bridge adjacent to Parken Pregan Bridge on the ATP.

· Houlaghans Creek crossing on River Rd

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 8 August 2024

RP-8

RP-8 Floodgate 15 A

Author: Andrew Mason

Director: Warren Faulkner

Summary:

The repair work on Floodgate 15A has been completed.

Recommendation

That the Floodplain Risk Management Advisory Committee receive and note the report in relation to repairs to Floodgate 15A.

Report

Floodgate 15A is a major component in the stormwater and flood infrastructure in the City of Wagga Wagga. It was initially constructed in 2008, damaged in the 2010 and 2012 floods, repaired in 2013 and became fully functional in 2016.

The pipe outlet at the base of the well shaft was compromised and a comprehensive repair and rehabilitation project has been completed to restore the floodgate to full functionality.

Stantec were engaged to provide engineering expertise and design of the repair and Huon were engaged as the contractor to complete the work.

The repair work was completed without any major issues and the levee, floodgate and pump have been returned to full functionality.

There were steps taken to minimise the risk of this type of damage reoccurring:

These included:

· A spigot plate on the inside of the well structure to protect the failed joint

· Guttering on the roof to stop water falling directly onto the levee

· Bracing in the levee to restrain the sheetpiles.