Flood Management Project Updates - August 2019

Wagga WaggaMajor Overland Flow Flood (MOFF) Risk Management Study and Plan

WMAwater has progressed a number of further flood modification options, since the presentation made to the Committee at the meeting of 18 June 2019 with the focus being the following areas in the city domain:

  • Bolton Park – optimising and increasing basin storage by reducing the size of the existing pipe through the park
  • Minor road regrading and earthworks around Adjin Street at Maher Street, to direct runoff into the drainage line (and keep it there)
  • Redhill Road raising (possibly as part of Glenfield Road Upgrade)
  • Wren Street swale drain
  • Incarnie Crescent – pipe regrading/ addition of new pipe
  • Improved basin function of Anderson Oval
  • Improve the Urana St basin function
  • Wollundry Lagoon Weir

In addition, further refinements have been made to the Lake Albert Options presented at the last meeting. Moving forward, WMAwater will be looking at all the options and selecting the most effective ones to progress further.

Given the topography, urbanisation and nature of overland flooding in Wagga, structural options tend to be most effective in a small, localised area rather than having far-reaching impacts across the city – it is unlikely that there will be ‘one option to rule them all’ in terms of reducing Wagga’s overland flood risk.

Therefore, in the coming weeks WMAwater will be looking at bringing all the preferred options together into a single “MOFFRMS masterplan” that can be adopted and implemented as opportunities arise in the future. This, along with smart planning controls and response measures, will reduce Wagga Wagga’s overland flow flood risk over time. WMAwater aiming to be able to present this to the Committee at the 1 October 2019 meeting.

Main City and North Wagga Levee

The upgrade of the remaining 6km of levee between Gobbagombalin Bridge and Hammond Avenue is the second part of this lengthy and complex project. The aim is to provide a 1 in 100-year flood protection to the city for the first time.

Stage 2 works involve the extension and reinforcement of existing concrete retaining walls and installation of capped sheet piles and extensive use of earthworks to raise the existing levee where possible.

The sheetpiles between Cadell Place and Johnston Street have been installed, adjusted for height and capping of these piles has commenced. The concrete path from Wiradjuri bridge to Johnston St has been completed. The concrete wall extension around the Watermark complex has been completed.

The carpark at Crampton Street has been reopened and the cribwall, stairs, footpath and DDA ramp completed with handrail installation to be completed shortly.

The Narrung St bank is completed and only waiting for seeding to take place and the area along the dog track is on track for completion shortly. The Wiradjuri Walking Track will be completely closed for several months in this section from January 2019.

The sheetpiles south of the Sturt Highway and along to Kooringal Road have been driven and levelled, the capping of these piles should commence shortly. The sheetpiles between the Riverina Water pedestrian bridge and the Sturt Highway have been driven and levelled, the capping of these piles should commence shortly.

Earthworks between the Railway Viaduct and the Riverina Water pedestrian bridge has commenced and should be completed shortly.

Residents and business operators affected by the works, or anyone interested in the Stage 2 levee project attended a community information session held on 30 May 2019.

Council staff are working with the contractors to minimise disruptions as much as possible and thank residents and businesses for their cooperation throughout these works.

There is effectively only 1600m of 9000m of levee still to be raised. The levee raising will be completed before the end of 2019 with ancillary works such as paths and capping to be completed early in 2020.

The Stage 2 upgrade is scheduled to take approximately 14 months, weather dependant.

Wagga Wagga Revised Floodplain Risk Management Study and Plan

Updates to FRMS&P Mitigation Measures

RE1: Improve Flood Warning System

As stated at the previous meeting, Council has made a grant application to investigate options to improve our riverine flood warning system. We are awaiting response in relation to the application, which will most likely be towards the end of the year. Some preliminary research has been conducted by Council staff in anticipation of the funding application being approved. There are official BOM and Office of Water Apps available that will facilitate the implementation of an effective system that provides early warning to the entire community along the floodplain.

R1: Improved Access to Oura

Council staff are undertaking further investigations into this recommendation.

R2: Improved Access to Gumly Gumly

Council has staff have contacted and provided information to Roads and Maritime Services (RMS) in respect to this recommendation. RMS will investigate options to raise the Sturt Highway as part of their ongoing rehabilitation program.

Wagga Wagga Villages Floodplain Risk Management Study and Plan

Work has progressed on the study particularly in regard to mitigation modelling, with a view to releasing a draft final report by the end of August. For mitigation work (selection of options and optimisation of same) community representatives are being engaged with, as a pre-cursor to further community engagement during the public exhibition phase.

It is anticipated that during the public exhibition phase the document will be made available on-line, in the public library and community meetings will be carried out with each village.

The draft final report will be presented to the committee for review and endorsement at the 1 October 2019 committee meeting. Once finalised the Wagga Wagga Villages Floodplain Risk Management Study and Plan will be reported to Council recommending it be placed on public exhibition.

Attached for the committee’s reference is the June 2019 Project Management Office report showing the current status and timelines of this project.

Flood Mitigation Option Feasibility Study for North Wagga & Floodplain Residents

Options PR1 & L4B

PR1: Undertake a feasibility study to investigate a Voluntary House Raising & Voluntary House Purchase Scheme in Wagga Wagga Study Area.

L4B: Undertake a feasibility study to investigate North Wagga Levee Upgrade to 5% AEP level of protection WITH an equivalent upgrade to Hampden Avenue (as embankment) and conveyance improvements through Wilks Park.

From WWCC, develop a third option as part of the study, a combination of the two measures (PR1 and L4B).

Council has received grant funding from OEH to undertake the feasibility study of these three options. Council staff have completed the scoping document for this project and are working on the development of the brief. Given the nature of the options to be investigated as part of the study, there is a level of complexity that needs to be fully considered and understood to ensure practical outcomes from the study.

The tender process needs to be finalised by the end of October 2019 to ensure the funding from OEH is utilised within the required timeframes

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