Takaka River Flood Hazard Project
This page details work on the Takaka River Flood Hazard Project, as well as reports and results following the initial phase of discussions with the community. It provides a summary and link to the latest Council resolution on the future direction of the project following feedback from the public.
If you have any questions, please contact Lisa McGlinchey.
- Project Background
- Potential Responses Considered
- Community Feedback
- Where to From Here?
- Cobb Dam Flood Management
In 2009 Council obtained detailed contour data for the Takaka area which enabled development of a computer model to better understand the flood hazard and the risk to the community from the Takaka River.
The results of the modelling were presented at a public open day in Takaka on 18 November at the Takaka Bowling Club. Discussions were also had on the potential responses available to the community. Around 80-100 people attended the open day.
Community feedback was invited on the modelling and an Issues and Options paper (below).
Following the initial community discussions and further consideration of the options, issues and feedback by Council staff, the following potential responses to the flood hazard risk were identified:
- Do Nothing / Status Quo - meaning continuing as we are currently and not seeking to do anything significant to reduce the flood hazard risk
- Engineered flood protection (for example the ‘draped stopbank’ scenario proposed by community members)
- Protection and management of flood flow paths (including potential remediation of already modified flow paths)
- Land use and building controls in Takaka township above Building Act requirements to further future-proof subdivisions and buildings
- Closure of residential zones with significant flood risks
- Change of existing undeveloped residential zone land to other urban or rural zoning
- Legal protection of the existing informal bank and/or its inclusion in the rivers assets management programme
There were positive and negative implications identified for each of these options that would still need to be investigated fully if the community wished to pursue them as a course of action. Many of the possible actions could have adverse impacts on other areas and important infrastructure, and these aspects would need to be understood and accounted for.
Gravel management was excluded as a practicable response due to the potential for significant adverse impacts and the significant extraction volumes required to produce a relatively small benefit.
These responses are discussed further in the Issues and Options Paper and the Community Feedback Summary Report.
Council received 21 individual responses during the feedback period. The level of feedback received was relatively low, representing approximately a quarter of those who attended the open day and approximately 3% of ratepayers within the model extent. This means the feedback may not necessarily reflect the majority view of the wider community and further consultation may be required to better define community expectations and concerns.
The feedback received is summarised in the report below. It also outlines Council staff’s consideration of the issues, options and feedback.
Given the limited amount of public feedback received, the Environment and Planning Committee decided on 29 March 2012 that the community feedback summary should be referred to the Golden Bay Community Board as a basis for further discussion and feedback from the Takaka community.
Following further discussion with staff and consideration of the information and public feedback, the Golden Bay Community Board made the following four recommendations to the Environment and Planning Committee:
- There appears to be no appetite in the local community for significant expenditure associated with a structural engineered response to the flood hazard risk from extreme flood events (>50yr ARI). Response to this risk should focus on planning methods including protection of flowpaths, land use and building controls and zone review to minimise the risks.
- There appears to be appetite in the local community for limited expenditure associated with small scale structural engineered responses to the flood hazard risk from small to moderate flood events (<20yrARI). Such responses would focus on providing a consistent level of protection from existing stopbanks and elevated land, including possible options for enhancement of these banks and discussions with the landowner regarding future Council legal access to and management of the bank. Other flood management measures, such as improving key urban flow paths, could also to be considered to further reduce flood risk from small to moderate flood events.
- Gravel extraction in specific locations, such as the Waingaro confluence and upstream of the Waitapu Bridge, is of interest to the community. The Community Board would like to see another Takaka River cross-section survey undertaken to provide information on the nature and extent of changes within the Takaka River bed since the last survey in 2006. This survey would help quantify any changes in bed morphology as a result of flood activity since 2006 and help determine if targeted gravel extraction would reduce the frequency of floodwater breakout in small to medium events (<20yrARI). General river management techniques should continue to be observed to maximise the overall main channel flood carrying capacity before breakout begins. Vegetation management, gravel relocation and where necessary, selected removal, should be done to reduce “pressure point” areas in the river”
- There is also interest in the local community to pursue options to improve stream health, including investigating possible reinstatement of flood flushing of the Te Kakau and Motupipi waterways, undertaking riparian planting to improve stream shading and investigating other landuse management methods to improve water quality.
Following consideration of the public and Community Board feedback and advice from staff, the Environment and Planning Committee resolved, at their 28 June 2012 meeting, to make recommendations to the Engineering Services Committee that further consideration be given to:
- undertaking a review of the current urban flood flow paths and possible remediation options to promote drainage of flood waters;
- investigating options in conjunction with the landowner, for Council involvement in management and potential enhancement of the existing informal stopbank south of the township; and
- investigating options for minimising breakout of floodwaters at key pressure points in the Takaka River and other potential engineered responses that may minimise the risk from flood events with less than a 20-year Average Recurrence Interval.
The Council decided not to continue any further planning work associated with the project, meaning all land use and building controls would remain as is, and that the existing zoning pattern would not be changed in response to the hazard.
View the meeting agenda, staff report and minutes, including Council resolutions using the links below:
- Agenda AEP12-06-28
- Report REP12-06-04 - Takaka River Flood Hazard Community Board Feedback Summary
- Minutes MEPC12-06-28
As there is no budget until Year 8 of the Long Term Plan for consideration of engineering-based options, the Takaka River Flood Hazard Project is effectively on hold and in a status quo situation for the short to medium term.
If you would like to discuss the outcome of the project to date, please contact a member of the Golden Bay Community Board.
Cobb Dam Flood Management
During the initial community discussions several requests were made for the flood management protocols for the Cobb Dam to be made available.
The two documents below are TrustPower’s key documents for emergency management of the Dam and release of water in flood events.
- Cobb Dam Flood Management Procedure 2011 (pdf, 223 KB)
- Cobb Dam Emergency Action Plan 2011 (pdf, 226 KB)
The Flood Management Procedure describes actions to be taken during heavy rain and floods which affect the Cobb Scheme. If at any time during the implementation of the Flood Management Procedure, it is obvious that the heavy rain has resulted in an Emergency, then the Emergency Action Plan for the Cobb Scheme is initiated.
An emergency situation is defined as “a situation that has the potential to seriously and adversely affect the environment, lives or property external to TrustPower”.
Examples of an Emergency are:
- Breach or potential breach or overtopping of the Cobb Earth Dam
- Rupture or potential rupture of Cobb penstocks