Te Kāuru Waipoua Flood Management Options

Masterton is a unique town in the Wairarapa that is built on the banks of the Waipoua River. Masterton District Council (MDC) and Greater Wellington Regional Council (GWRC) acknowledge that parts of Masterton urban area are in a flood hazard area that may be impacted in a significant and infrequent flood, an event that has 1% chance of occurring in any year.

We are looking at ways to manage current and future flood risks. This is being done through the Te Kāuru Upper Ruamāhanga Floodplain Management Plan.

MDC and GWRC have jointly updated flood hazard maps for the Waipoua River that are still in draft and pending an independent audit that is expected to be completed over the next few months. The maps show that there is likely to be less impact on Masterton than initially thought. However, there are still areas such as Mawley Park, and parts of Oxford Street and Akura Road that are likely to be flooded.

We are looking at a range of potential river management approaches that work with the natural processes of the river, provide hazard mitigation and deliver wider benefits to the community. The approaches considered are likely to be implemented in stages and will ensure a long term and sustainable approach. Further areas of higher immediate risk can be identified, and work undertaken to manage these risks earlier in the delivery programme.

A key role of local authorities is to work with communities to protect them from the effects of hazards including flooding. To do this, we all need to understand the flood risk, put affordable and acceptable flood protection in place and ensure inappropriate development doesn’t create new problems.

Want to find out more about the flood management approaches?

Flood management approaches

Several different flood management approaches are being considered to develop effective flood management options for Masterton:

Upgrade or construct stops

Upgrade or construct stopbanks

Permanent flood defence structures that prevent flood water from leaving the river

  • Investigate whether upgrades to the existing stopbanks are appropriate and where strengthening would be required
  • Explore where new stop banks could be located to allow greater conveyance during floods
  • Establish or maintain flood walls and stopbanks

Improve conveyance of flood water

Increase the flow rate and volume that can be contained within the Waipoua River

  • Explore locations where the channel capacity could be improved by removing flow restrictions
  • Remove and/or raise structures
  • Widen and/or deepen the channel
  • Consider what river corridor maintenance is required

Increased upstream storage

Hold back some flood water upstream of the urban area

  • Utilise or enhance the existing floodplain away from at-risk areas to store more water in a flood
  • Reduce the peak flow of a flood
  • Identify opportunities for alternative land uses in storage areas that have low vulnerability to flooding

Flood resilience and community preparedness

Management flood waters beyond the river

  • Control land uses in the floodplain
  • Raise floor levels of housing
  • Investigate improvements to the flood warning system
  • Temporary or mobile flood defences
  • Community education and preparedness support

Catchment Management

Aim to reduce the speed and runoff of water down the river catchment

  • Consider how the river reaches upstream of Masterton influence flooding
  • Establish buffers including planting vegetation and consideration of wetlands upstream
  • Establish alternative land uses in the catchment

More information on the flood management options, including diagrams


A note on terminology

Our focus is on understanding the spread and depth of flood waters in an infrequent flood. Often this size of flood is referred to as a 1-in-100 year flood, we call it a 1% annual chance flood; it means there is a 1% chance of this sized flood occurring in any given year. It does not mean that there is exactly one of these floods every 100 years. It is also important to remember that several big floods could happen in quick succession.

Updated information

In 2014, Greater Wellington Regional Council shared its understanding of the spread of flooding across urban Masterton in one of these 1% annual chance floods.

Thanks to access to better information, technology and local knowledge we now have a more accurate picture of what a significant and infrequent flood would look like in Masterton. The modelling has been revised and updated in collaboration with Masterton District Council and new flood-hazard maps were developed.

The new maps, which are still in draft pending an independent audit, shows a future 1% annual chance flood is likely to have less impact on the Masterton urban area than initially thought. However, it shows some areas of the Masterton urban area are likely to experience flooding in a 1% annual chance flood. This is mainly around Oxford Street and areas bordering Akura Road. The depth of flooding varies depending on the scenario being considered; most is likely to be below 30cm, but some areas may experience flooding up to two metres.

Work has also been done to model what a flood will look like in the future (circa 2090) with the impacts of climate change factored in. In this scenario, the flooding spreads across the urban area to the south west of the Waipoua River, including the central business district. However, this flood spread is smaller than what was initially thought in 2014.

Community feedback

In December 2018 we will be meeting with members of the Masterton community to provide answers to questions that you may have on the flood management options that are being developed. GWRC and MDC are happy to provide more detail and answer your queries on the flood management approaches. Note that the regulatory implications (e.g, new building levels) will be confirmed prior to final flood-hazard maps being produced.

For more information, download a copy of:

Waipoua 1% AEP Flood Event - including climate change (town centre only)

Keen to talk to someone about Waipoua flood management options?

Email the project team at tekauru@gw.govt.nz or phone them on 0800 496 734


Masterton is a unique town in the Wairarapa that is built on the banks of the Waipoua River. Masterton District Council (MDC) and Greater Wellington Regional Council (GWRC) acknowledge that parts of Masterton urban area are in a flood hazard area that may be impacted in a significant and infrequent flood, an event that has 1% chance of occurring in any year.

We are looking at ways to manage current and future flood risks. This is being done through the Te Kāuru Upper Ruamāhanga Floodplain Management Plan.

MDC and GWRC have jointly updated flood hazard maps for the Waipoua River that are still in draft and pending an independent audit that is expected to be completed over the next few months. The maps show that there is likely to be less impact on Masterton than initially thought. However, there are still areas such as Mawley Park, and parts of Oxford Street and Akura Road that are likely to be flooded.

We are looking at a range of potential river management approaches that work with the natural processes of the river, provide hazard mitigation and deliver wider benefits to the community. The approaches considered are likely to be implemented in stages and will ensure a long term and sustainable approach. Further areas of higher immediate risk can be identified, and work undertaken to manage these risks earlier in the delivery programme.

A key role of local authorities is to work with communities to protect them from the effects of hazards including flooding. To do this, we all need to understand the flood risk, put affordable and acceptable flood protection in place and ensure inappropriate development doesn’t create new problems.

Want to find out more about the flood management approaches?

Flood management approaches

Several different flood management approaches are being considered to develop effective flood management options for Masterton:

Upgrade or construct stops

Upgrade or construct stopbanks

Permanent flood defence structures that prevent flood water from leaving the river

  • Investigate whether upgrades to the existing stopbanks are appropriate and where strengthening would be required
  • Explore where new stop banks could be located to allow greater conveyance during floods
  • Establish or maintain flood walls and stopbanks

Improve conveyance of flood water

Increase the flow rate and volume that can be contained within the Waipoua River

  • Explore locations where the channel capacity could be improved by removing flow restrictions
  • Remove and/or raise structures
  • Widen and/or deepen the channel
  • Consider what river corridor maintenance is required

Increased upstream storage

Hold back some flood water upstream of the urban area

  • Utilise or enhance the existing floodplain away from at-risk areas to store more water in a flood
  • Reduce the peak flow of a flood
  • Identify opportunities for alternative land uses in storage areas that have low vulnerability to flooding

Flood resilience and community preparedness

Management flood waters beyond the river

  • Control land uses in the floodplain
  • Raise floor levels of housing
  • Investigate improvements to the flood warning system
  • Temporary or mobile flood defences
  • Community education and preparedness support

Catchment Management

Aim to reduce the speed and runoff of water down the river catchment

  • Consider how the river reaches upstream of Masterton influence flooding
  • Establish buffers including planting vegetation and consideration of wetlands upstream
  • Establish alternative land uses in the catchment

More information on the flood management options, including diagrams


A note on terminology

Our focus is on understanding the spread and depth of flood waters in an infrequent flood. Often this size of flood is referred to as a 1-in-100 year flood, we call it a 1% annual chance flood; it means there is a 1% chance of this sized flood occurring in any given year. It does not mean that there is exactly one of these floods every 100 years. It is also important to remember that several big floods could happen in quick succession.

Updated information

In 2014, Greater Wellington Regional Council shared its understanding of the spread of flooding across urban Masterton in one of these 1% annual chance floods.

Thanks to access to better information, technology and local knowledge we now have a more accurate picture of what a significant and infrequent flood would look like in Masterton. The modelling has been revised and updated in collaboration with Masterton District Council and new flood-hazard maps were developed.

The new maps, which are still in draft pending an independent audit, shows a future 1% annual chance flood is likely to have less impact on the Masterton urban area than initially thought. However, it shows some areas of the Masterton urban area are likely to experience flooding in a 1% annual chance flood. This is mainly around Oxford Street and areas bordering Akura Road. The depth of flooding varies depending on the scenario being considered; most is likely to be below 30cm, but some areas may experience flooding up to two metres.

Work has also been done to model what a flood will look like in the future (circa 2090) with the impacts of climate change factored in. In this scenario, the flooding spreads across the urban area to the south west of the Waipoua River, including the central business district. However, this flood spread is smaller than what was initially thought in 2014.

Community feedback

In December 2018 we will be meeting with members of the Masterton community to provide answers to questions that you may have on the flood management options that are being developed. GWRC and MDC are happy to provide more detail and answer your queries on the flood management approaches. Note that the regulatory implications (e.g, new building levels) will be confirmed prior to final flood-hazard maps being produced.

For more information, download a copy of:

Waipoua 1% AEP Flood Event - including climate change (town centre only)

Keen to talk to someone about Waipoua flood management options?

Email the project team at tekauru@gw.govt.nz or phone them on 0800 496 734


  • CLOSED: This survey has concluded.

    Which of the flood management approaches do you support?

    With access to better and updated information, technology and local knowledge, we now have a more accurate picture of what a significant and infrequent flood would look like in Masterton. Based on updated flood hazard maps that are still in draft, GWRC and MDC are considering a range of flood management approaches to protect community and assets in the event of 1% chance flooding in future. Have Your Say by 13 December 2018.


    With access to better and updated information, technology and local knowledge, we now have a more accurate picture of what a significant and infrequent flood would look like in Masterton. Based on updated flood hazard maps that are still in draft, GWRC and MDC are considering a range of flood management approaches to protect community and assets in the event of 1% chance flooding in future. Have Your Say by 13 December 2018.


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