Ngongotahā Flood Review Project

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The Ngongotahā Flood Review Project is a joint Rotorua Lakes Council and Bay of Plenty Regional Council programme of action to implement the 24 recommendations of an Independent Review Panel relating to the Ngongotahā flood event of 29 April 2018.

The programme of work covers six areas:

  • Clarification of roles and responsibilities
  • Stream repairs and maintenance
  • Engineering, modelling and options
  • Civil defence and readiness
  • RMA planning and consents
  • Upper catchment considerations

Each area relates to a cluster of recommendations within the Panel's report.

The Independent Review Panel report can be accessed here.

The Ngongotahā Flood Review Project is a joint Rotorua Lakes Council and Bay of Plenty Regional Council programme of action to implement the 24 recommendations of an Independent Review Panel relating to the Ngongotahā flood event of 29 April 2018.

The programme of work covers six areas:

  • Clarification of roles and responsibilities
  • Stream repairs and maintenance
  • Engineering, modelling and options
  • Civil defence and readiness
  • RMA planning and consents
  • Upper catchment considerations

Each area relates to a cluster of recommendations within the Panel's report.

The Independent Review Panel report can be accessed here.

  • Ngongotahā Action Plan - April 2020 update

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    14 Apr 2020
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    Reflecting on 2019

    A new project report has been released, which provides a snap shot of work carried out over the last year associated with the Ngongotahā Action Plan. This report can be accessed here:
    Ngongotahā Action Plan: A year in review (Jan - Dec 2019)

    A large number of actions have been achieved and/or are ongoing (in green to the right). A number of actions are still in progress, although running behind schedule (in red to the right). These actions, discussed further overleaf, relate to:

    A large number of actions have been achieved and/or are ongoing (in green to the right). A number of actions are still in progress, although running behind schedule (in red to the right).

    These actions, discussed further, relate to:

    • Analysis of flood mitigation options and associated engagement with the Ngongotahā Community.
    • Completion of the stream maintenance plan.
    • Establishment of the working group for the Ngongotahā Community Response Plan.
    • Review of the District Plan.
    • Construction of detainment bunds in the upper catchment.

    Achievements for 2019 include the:

    • Completion of priority stream repairs from the April 2018 flood and removal of 30 large and at-risk trees from the upper catchment.
    • Establishment of the Ngongotahā Community Reference Group (CRG) to guide the dual-Council project team, particularly in relation to potential flood mitigation options and community engagement.
    • Successful operation of dual-Council teams, particularly in relation to RMA planning; engineering options as well as communication and engagement.
    • Completion of a number of actions which have resulted in improved internal processes and working relationship between the two Councils.

    Overall the project team has worked hard to complete, or at least progress the actions to address the matters within the independent review panel report.

    The focus for 2020 is the completion of the ‘in progress’ actions, in particular, the analysis of, and engagement on, the flood mitigation options for Ngongotahā. Showing ‘real’ progress in terms of flood mitigation for the affected residents will be crucial this year.

  • NGONGOTAHĀ FLOOD REVIEW PROJECT - DECEMBER 2019 UPDATE

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    17 Dec 2019

    The Ngongotahā Flood Review project aims to reduce the risk and impact of future storm events in Ngongotahā. This flyer provides an update on some of the recent work we've completed, particularly in relation to upcoming stream maintenance works and the assessment of potential flood mitigation options. It's been a busy few months since our last update in September and we'll provide another update on progress in February next year.

    STREAM BANK REPAIRS AND MAINTENANCE
    In the past two months, preparations and planning for summer maintenance works have been finalised and development has continued on the longer-term maintenance plan. To minimise risk and avoid future damage, a number of large trees were removed in the upper catchment area.

    A lot of work was completed last summer and, as we move into Summer 2019 / 2020 that will continue including activity near the A&P Showgrounds and further large tree removal, vegetation management, fencing, tree planting and fish habitat restoration.

    Over summer, existing spillways (pathways that carry away surplus water) will be enhanced by contouring, weed control, and placing rockwork to strengthen inlets and outlets.

    CIVIL DEFENCE AND READINESS PLANNING AND CONSENTS
    We've completed the Emergency Evacuation Plan for the Ngongotahā catchment. A working group has been established for the Paradise Valley Community Response Plan and potential members have been identified for the working group to develop the Ngongotahā Village Community Response Plan.

    A workshop will be held regarding the Ngongotahā Village Community Response Plan with the goal to complete the Community Response Plans for the Ngongotahā and Paradise Valley communities in 2020. We'll let people know the dates for these workshops once confirmed.

    PLANNING AND CONSENTS
    Scoping is still underway regarding the District Plan review with additional risk assessments required by BOPRC to satisfy Regional Policy Statement requirements. Over the coming months RLC and BOPRC will work together to develop and review current urban flood hazard catchment models with a view to using this to develop flood risk assessments for these catchments to, in turn, inform a review of the District Plan.

    FLOOD MITIGATION OPTIONS
    An initial ‘high-level list’ of options was assessed using a 12-point criteria, which considered features including hydrology, water quality, ecology, land ownership, cultural aspects and likely costs. Six options were selected in conjunction with the Community Reference Group in August.

    We are seeking flood mitigation options that will:

    • Accommodate a possible 'one in one hundred' year event (1% AEP = a 1 percent Annual Excedence Probability, i.e. a 1 in 100 chance that a river will experience a flood of that size in any given year).
    • Maintain the Ngongotahā Stream's environmental and recreational values.
    • Allow for climate change.
    • Take an adaptive approach i.e. options that can be enhanced in the future

    The three upper-catchment (Above State Highway 5) options are being worked through by Bay of Plenty Regional Council’s Rotorua-based Land Management team. These options involve conversations with landowners about creating detention bunds which hold and slow stormwater; protecting areas vulnerable to erosion; and exploring land-use changes.

    Meanwhile, the lower-catchment (Below State Highway 5) options are being modelled and the three options are as follows:

    • Raising Western Road - This option looks at raising a section of Western Road either side of the intersection with Brake Road. The heightened road level would act as a flood defence.
    • Overland flow path - This option looks at creating a flow path to the south of the stream to convey water in times of flood, diverting it away from residential areas.
    • High flow bypasses - This option would enhance existing bypasses and look to create others at sections of the stream where water naturally ponds in times of high flow.
    Modelling the stream & rainfall
    Modelling uses data to simulate flood events, enabling engineers to see how a river or stream, and its flood defence systems, will be affected by various factors, including volumes of water, durations of rainfall and design elements. The model is repeated multiple times with different scenarios and each ‘run’ can take two or three days to complete.

    Next Steps:
    Further modelling is currently underway to find out which of the options (by themselves or combined) will be most effective in safeguarding the Ngongotahā community in the future.
  • Ngongotahā Action Plan workstream update

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    19 Sep 2019

    The Ngongotahā Flood Review (NFR) project is aimed at reducing the risk and impact of future storm events in Ngongotahā. The Ngonogtahā Action Plan was developed by the Rotorua Lakes Council, Bay of Plenty Regional Council, the Community Reference Group and the wider community to achieve the project objectives.

    The NFR project is split into five work streams. Each one has objectives based on recommendations made by the Independent Flood Review Panel. Here’s a snapshot of what’s been completed since our last update in July.

    Stream repairs and maintenance

    • A detailed work programme has been developed for the next 12 months that includes general vegetation maintenance and planting, repairs to erosion sites, maintenance to overflow paths. A stream maintenance plan is also being prepared to include scheduling for inspections and maintenance standards.
    • A community planting day was held on August 24 with one thousand grasses and sedges planted along the Ngongotahā Stream.

    Engineering, modelling and options

    • The list of flood mitigation options has been reduced from 12 to 6. Modelling will soon commence to find out whether these options (by themselves or combined) will be effective.

    Civil defence and readiness

    • A Community Response Plan is in development for Paradise Valley. The focus has been on bringing residents together to form a working group for initial development of a plan.
    • On-going discussions are being had with various groups and individuals within Ngongotahā to encourage participation in developing a plan for Ngongotahā community.
    • A recent survey highlighted that just over half of those surveyed in affected areas in Ngongotahā and Paradise Valley did not have a family emergency plan or emergency kit prepared.
    • The Ngongotahā Stream Emergency Resilience and Evacuation Plan is available for consultation by the community.

    RMA planning and consents

    • We’ve reviewed the Engineering Code of Practice. Council is intending to adopt and adapt Waikato Regional Council’s Regional Infrastructure Technical Specifications (RITS).
    • Scoping is underway to review Council's 'rule book' (District Plan) to identify potential improvements regarding development near flood-risk areas.

    Upper catchment considerations

    • A drone survey was completed for the Taurangamiromiro Stream from Relph Road to the Lion Park.
    • Water quality monitoring has commenced at 9 sites and on-going monitoring will occur monthly over the next 12 months.
    • Large tree removal at Taurangamiromiro Stream to commence in October.
    • Future work – further surveillance and maintenance planning of the stream from the Lion Park down to SH5.
    • Continuing to work with landowners interested in land use change and riparian protection

    Clarification of roles and responsibilities

    • BOPRC and RLC signed an MOU in July clarifying their respective roles and responsibilities relating to the maintenance of Ngongotahā Stream.
    • Next steps involve building awareness of frontline staff.

    Connecting the Ngongotahā Community

    • Meetings have been held with local community groups to share what we've been doing.
    • Two planting days were held on the 2nd & 24th of August
  • Ngongotahā Community Reference Group

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    by Amoran, 22 May 2019

    As part of this project a Community Reference Group has been formed to assist both councils to collaborate and effectively connect with the affected community and iwi, and to ultimately ensure that any action plan options chosen, are balanced, practical, affordable, deliver the risk reduction that the local people need and don't create new issues or flooding

    The Community Reference Group will perform and support the following:

    • Filter/narrow down the flood reduction/mitigation options that are realistic, pragmatic, appropriate and acceptable to the Ngongotahā catchment community
    • Assist interpreting and communicating flood modelling and mitigation options so they are understandable to the wider public
    • Being a conduit for BOPRC & RLC to connect with the wider community
    • Assisting in engagement with the wider community on the proposed programme of works and help in seeking wider community input

    More information on the Community Reference Group and the role here.


  • Project Background

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    22 May 2019

    Following a significant rain event on 29 April 2018, the Ngongotahā Stream overtopped its banks and flooded parts of the Ngongotahā township near Rotorua. The Rotorua Lakes Council and Bay of Plenty Regional Council have worked together since then, alongside other agencies, to assist the community to recover from this event. The councils commissioned an independent review of the flood event to understand the cause of the flooding and how similar flood impacts may be avoided in the future. This report was presented to the councils’ elected members on 10 December 2018.

    To facilitate the implementation of the 24 recommendations of the Independent Review of the Ngongotahā Flood Event report, four senior managers of the two councils will jointly lead a series of actions over coming months. They have appointed an independent project management expert , to ensure the key work streams are identified, evaluated, sequenced and stay on task. That progress with each workstream is well communicated.

    A key recommendation of the four senior managers was to form a Community Reference Group who can assist the councils to collaborate and effectively connect with the affected community and iwi, and to ultimately ensure that any structural works option chosen, are balanced, practical, affordable and deliver the risk reduction that the local people need.

  • Ngongotahā flood event

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    by Amoran, 22 May 2019

    On Sunday 29 April 2018, the Rotorua district was subject to a severe weather event. The rainfall depth over a six-hour period in the areas around the Ngongotahā catchment reached 145mm, with 62.5mm of rain falling in one hour.

    The Ngongotahā Stream reached its highest recorded level and overflowed its banks in several places. While flooding occurred throughout the Rotorua district, the Ngongotahā catchment experience was extreme and resulted in floodwaters inundating many homes and several businesses. Over that time 38 houses were declared insanitary and required extensive repair work. Some businesses were closed for days while they undertook repairs.

    More information about the Flood Recovery can be found here.

  • Work completed to date

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    by Amoran, 22 May 2019
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    In the weeks and months following the flood, both Councils faced significant repairs to infrastructure.

    This included stopbanks, roading and stormwater network as well as the banks of the Ngongotahā Stream.