Gore flood protection upgrade

The priority areas of work to late Spring 2023 are:

• Construction of new stop bank along Ontario and Toronto Streets to replace the existing concrete flood protection wall
• Alterations, replacement and installation of existing and new storm water culverts
• Removal of high-risk trees and tree stumps on the true right stop bank in Gore township along River and Richmond Streets

The planned tree removal, completed in April-May 2023, was part of our wider maintenance programme, which involves assessing trees on stop banks throughout the region. Work to remove the remaining tree stumps and re-grass these areas is expected to be completed by November 2023.

Trees and shrubs on and close to stop banks can interfere with the integrity of the stop bank and potentially lead to the banks failing. The roots of trees and vegetation can weaken stop banks; during a flooding event, water can begin flowing through this weak patch, often leading to a rapid failure. Trees can also be toppled in heavy winds, creating holes for water to flow through. Tree debris becomes a hazard during a flood, which can cause damage to infrastructure.

There will be some disruptions to the movement of traffic, cyclists and pedestrians while the work is underway. We will implement temporary traffic management plans to mitigate the increase in heavy transport vehicles and construction machinery, resulting in increased travel times. Temporary road, footpath and cycle track closures and detours will also be necessary.

Benefits

• The upgraded flood protection network will provide adequate near-term protection for Gore's community, infrastructure and property against floods up to the current design level
• The design of the proposed works is 'future proofed', meaning that the height of the upgraded stop banks could be more easily raised in the future if appropriate
• Work completed with central government funding assistance
• Alignment with Gore District Council's flood-proofing work

Project status (15 September 2023)

• Establishment of a collaborative working group with Gore District Council
• Survey, geotechnical and engineering design work completed
• Engagement with landowners ongoing
• Community engagement ongoing
• Construction contract awarded to Linton Contracting Ltd. December 2022
• Public drop-in sessions to inform the community about associated stop bank maintenance, including removal of high-risk trees, in late February 2023
• Tree work completed April-May 2023
• Alterations, replacement and installation of existing and new storm water culverts completed
• Construction of a new stop bank along Toronto and Ontario Streets underway (May 2023), including the transfer of gravel from the gravel island downstream of Mataura Bridge

Next steps

• Completion of earthworks for new stop bank along Toronto and Ontario Streets expected by mid-October, and re-grassing and re-fencing as weather and ground conditions permit
• Removal of tree stumps and associated earthworks on River and Richmond Street stop banks to be completed by November 2023
• Completion of 2D hydraulic modelling for the Mataura, including Gore
• Further community engagement
• Use 2D hydraulic modelling to better understand the capacity and integrity of existing flood protection infrastructure and determine the best design solutions for the next phase of climate resilience work