Agenda of Floodplain Risk Management Advisory Committee

Reports submitted to the Floodplain Risk Management Advisory Committee to be held on Wednesday 15 May 2024.

Floodplain Risk Management Advisory Committee AGENDA AND BUSINESS PAPER

Wednesday 15 May 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 FEBRUARY 2024 & 27 FEBRUARY 2024 2

DECLARATIONS OF INTEREST 2

Reports from Staff

RP-1 2018-19-FM-0071 - North Wagga Flood Mitigation Options 3

RP-2 2021-22-FM-0039 - Lake Albert Flood Mitigation Options - Feasibility Study 11

RP-3 2021-22-FM-0032 - Uranquinty Levee Upgrade - Investigation and Design 12

RP-4 2022-FMP-0103 Humula and Mangoplah Flood Studies 15

RP-5 DCCEEW 2024 Floodplain Grants 16

RP-6 Floodgate 15 A 17

RP-7 Flood Project Implementation Status 19

QUESTIONS WITH NOTICE 40

ACKNOWLEDGEMENT OF COUNTRY

APOLOGIES

Confirmation of Minutes

CM-1 FLOODPLAIN RISK MANAGEMENT ADVISORY COMMITTEE MINUTES - 15 FEBRUARY 2024 & 27 FEBRUARY 2024

Recommendation

That the Minutes of the proceedings of the Floodplain Risk Management Advisory Committee Meeting held on 15 February 2024 & 27 February 2024 be confirmed as a true and accurate record, noting Council’s adoption of these minutes at its meeting 11 March 2024.

Attachments

1 ⇩.	FRMAC Minutes - 15 February 2024	41
2 ⇩.	FRMAC Minutes - 27 February 2024

DECLARATIONS OF INTEREST

Report submitted to the Floodplain Risk Management Advisory Committee on Wednesday 15 May 2024

RP-1

Reports from Staff

RP-1 2018-19-FM-0071 - North Wagga Flood Mitigation Options

Author: Andrew Mason

Director: Phil McMurray

Summary:

The project has reached finalisation and the consultant is presenting the final report and recommendations for adoption.

Recommendation

That the Floodplain Risk Management Advisory Committee receive and note the final report and recommends to the Council that it receive and adopt the report and the recommendations in full.

Report

As per the scope and brief of this study the consultant CIE, Woolcott, WMAwater and NGH have completed the four key areas of analysis:

· Economic

· Environmental

· Social

· Cultural

In discussion with this committee, the final report has been developed to reflect the findings of this analysis and has the following conclusion for Flood Mitigation for North Wagga:

Of the different options that could be adopted:

– The combined L4A with a targeted VHR/VHP to high risk residents outside North Wagga delivers the best outcome for the community. However, there may be challenges for some households due to accessibility issues which could result in additional costs above the assumed $120,000/property raising.

– L4B by itself or in combination with any other strategies is too expensive to be cost effective, regardless of the size of potential benefits.

– VHR and VHP delivers positive outcomes for the community where it is applied to high risk properties where the risk reduction is greater than the cost of the actions. This suggests a strategic approach to the application of these policies based on estimated risk reduction. Further, the VHP policy could be more efficient where the purchase applies only after flooding. A pre-emptive policy would immediately “destroy” the value of the property with certainty, compared to the comparatively low probability of this. An alternative would be to purchase a property pre-emptively but maintain it as part of the housing stock until it is damaged by a flood event which could be in, say, 10 years’ time.

In implementing the proposed levee it is important to recognise that water is diverted to other parts of the floodplain, potentially negatively impacting on some properties. However, where negative impacts occur these are typically only result in minor increases flood depths. The risk reduction benefits of the levee substantially outweighs the potential negative impacts on some properties.

Based on the draft report the FRMC had developed the following likely recommendation for Council:

a. Upgrading the existing North Wagga Levee system (Stage 1 of L4B - 5% AEP (1 in 20)) and offering Voluntary House Raising and Purchase subject to risk reduction and cost effectiveness

b. Increasing the road heights and bridges along Hampden Ave to provide a safe evacuation route (Stage 2 of Option L4B) subject to funding.

Public Exhibition

Public exhibition of the Flood Mitigations Options for North Wagga was required by the Local Government Act (1993, Section 38). This section stipulates that Council must exhibit the draft plan for public comment for a period of at least 28 days, and that submissions must be considered by the council before the plan is endorsed or amended.

The Draft Report was endorsed for public exhibition at the Council meeting on the 11 March 2024. The Public Exhibition period commenced on the 15 March 2024 and was closed on the 26 April 2024, after a period of 42 days.

Digital copies of the report were available on the Council website through the “Have Your Say” page and one on one sessions with Council Officers were available to be booked through this page.

The Reports, as attached, were presented for public exhibition, and included:

· Flood Mitigation Options for Wagga Wagga, Evaluation of options (CIE, Feb 2024)

· Flood Mitigation Options for Wagga Wagga, Evaluation of options (CIE, Oct 2023)

· North Wagga Flood Mitigation Community Engagement Report Phase 2 (Woolcott Research, 2024)

· North Wagga Flood Risk Mitigation Community and stakeholder Engagement Study (Woolcott Research, 2023)

· Assessment of Environmental Constraints North Wagga Flood Mitigation Options (NGH, 2023)

· Biodiversity Assessment Report North Wagga Flood Levee (NGH, 2023)

· Flood Impacts of Flood Mitigation Options for North Wagga (WMA Water, 2024)

There were six submissions received from the public and one from Biodiversity Conservation and Science during the PE period and an outline of these is included as an attachment to the final report.

The three submissions and the three one on one meetings did not highlight any significant problems or concerns with the proposed mitigation options.

The submission from Biodiversity Conservation and Science stated:

BCS has reviewed the Biodiversity Assessment Report North Wagga Flood Levee (NGH 2023). We agree the proposed works are likely to cause significant impact on threatened species. While that impact is likely to vary depending on the option(s) that are eventually built, we consider it important to determine the precise nature of that impact per option, and to use that information iteratively to avoid and minimise harm to biodiversity.

Given significant impact is likely, section 7.12(3) of the Biodiversity Conservation Act 2016 establishes Council is not to give consent without either the concurrence of the Environment Agency Head or a Biodiversity Assessment Development Report (BDAR). The review of environmental factors (REF) established by Part 8 of the Environmental Planning and Assessment Regulation 2021 is a good opportunity for Council to decide which of those two pathways best suit the activity. Given the proposed activity involves various options, we strongly recommend a BDAR is the best approach.

The BDAR relies on a method that will determine which option best avoids and minimises harm, mitigation measures that can be applied locally to maintain habitats and populations in situ, and price offsets per option to inform Council’s decision. The BDAR will also rely on the Biodiversity Offset Scheme to mitigate harm. That approach means Council does not have the ongoing burden of managing offset work.

The initial information Council has is that a BDAR will take 15-18 months to complete and has a cost of approximately $100,000.

Implementation timeline for adopted recommendation

Stage	Duration	Commencement
Topographic Survey	6 months	August 2024
Voluntary House Raising (VHR) and Voluntary House Purchase (VHP) project development and implementation	3-5 years	January 2025
Environmental Assessment	18 months	September 2024
Civil Design	12-15 months	July 2025
Levee contractor procurement	4 months	November 2026
Levee construction	24 months	March 2027

There are some significant issues that the committee need to be aware of regarding the recommendations from this report.

Evacuation Level for North Wagga

With the existing levee in place, the current evacuation trigger for North Wagga is a river height of 9.3m. The existing road network around North Wagga is inundated at a river height of approximately 9.4m. The “banks” along Hampden Ave between the Wiradjuri Bridge and Parken Pregan Bridge adjacent to Wilks Park are not keyed into the underlying ground and cannot be assumed to offer a safe evacuation route beyond the existing 9.3m. The Mill St causeway between East St and the Marah St is inundated at 9.4m and the East St section of North Wagga becomes isolated beyond this river height.

If a 10.1m levee plus freeboard is constructed around North Wagga and the existing road network or the “banks” are not modified then the evacuation trigger for North Wagga will probably remain at 9.3m.

The NSW State Emergency Service have been consulted regarding this issue and have provided the following response:

The NSW SES further recommend:

· Continuing to progress flood mitigation and management options in accordance with the NSW Flood Prone Land policy as set out in the Flood Risk Management Manual 2023 (the Manual) and supporting guidelines. This would include a detailed assessment during the next phase of the mitigation process to understand flood behaviour and constraints.

· Investigating ways to improve emergency access and egress during a flood.

· Carefully considering any locations of proposed increase in density of development and its associated increased risk to life and property. This flood mitigation option will address some residual risk to life and property.

· Considering Development Control Plan 2010 (DCP) which strengthen the land use planning process to identify areas where risk to life from flooding is intolerable.

The second point in the above extract may allow Council to investigate the formalisation of the Wilks Park banks to enable the construction of similarly sized banks to a suitable standard to allow them to be licenced as levees and potentially for the SES and Council to raise the evacuation trigger for North Wagga to a level closer to the design height of the new levee.

The secondary issue with evacuation and egress is that the residents along East St will possibly still have to evacuate at 9.3m. Mill St between East St and the ring levee becomes inundated at around 9.3m - 9.4m.

There is no simple infrastructure solution to this and it may require the new levee design to incorporate a helicopter rescue pad into the East St levee for emergency evacuations.

If the banks along Wilks Park are formalised, the section of North Wagga protected by the ring levee will still be able to evacuate at 9.7m while the section of North Wagga along East St will need to evacuate at approximately around 9.3m.

Newly Inundated Houses

If a 5% AEP levee is constructed around North Wagga without the excavation to offset the displacement of water, there will be adverse effects to over 1100 other houses. In a larger flood event (1 in 200, 1 in 500) when the main city levee is overtopped there will be increased water in a significant number of houses. These houses already have over floor flooding but will have an increased amount of water of up to 200mm flowing through them.

There are a few properties that will now be flood affected that weren’t previously inundated around East Wagga in a 5% AEP. Those 25 properties will be part of the targeted VHR/VHP program.

Funding

· Council has $6.3M in funding raised through the levee Special Rate Variation (SRV)

· Council has $1M available through the CDG0789 grant, this must be expended by December 2025

· Council has applied for the next round of BCS DCCEEW Floodplain grants for $5M to allow for the environmental analysis, detailed design and construction of the North Wagga levee system

· Council has applied for the next round of BCS DCCEEW Floodplain grants for a VHP and VHR feasibility Scoping Study for the 25 houses that will be adversely affected by the construction of Stage 1 of the Flood mitigation options for North Wagga.

This final report is being presented to the committee for acceptance and the committee is required to recommend to Council that it receive the report and accept the recommendations in full. A detailed report will then be presented for consideration at the Council meeting on 27 May 2024.

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

The Committee are advised that the consultants will attending this meeting remotely and presenting via zoom.

Attachments

CIE Report_Wagga Wagga CC_Flood Mitigation Options - Provided under separate cover

Report submitted to the Floodplain Risk Management Advisory Committee on Wednesday 15 May 2024

RP-6

RP-6 Floodgate 15 A

Author: Andrew Mason

Director: Phil McMurray

Summary:

The repair of Floodgate 15A is being undertaken and reinstatement of the levee, placement of the pipe collar and replacement of the footpath is nearing completion.

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 has been compromised and an immediate repair and rehabilitation project has begun to restore the floodgate to full functionality.

Stantec were initially contracted to undertake engineering assessment of the issue and to develop an immediate repair and long-term solution. Huon and Tye Jackson Welding were engaged to implement the solution developed by Stantec and Council. The project is being undertaken to the required specifications with the levee repaired, the failed grout replaced with a more suitable product and the stainless-steel sleeve installed to protect the pipe/wall connection from water turbulence in the future.

Financial Implications

The DRFA funding of $1M from the Office of Local Government NSW has been identified to complete this repair project, the project is on track to be completed within the allocated budget.

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

1 ⇩.	Flood Studies Project Status - FRSMP 2018
2 ⇩.	Flood Studies Project Status - EWS
3 ⇩.	Flood Studies Project Status - MOFFS 2021
4 ⇩.	Flood Studies Project Status - VOFFS 2021