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Plan Change 27 – Flooding from intense rainfall

Plan Change 27 – Flooding from intense rainfall introduces a new rule framework to manage the effects of flooding in intense rainfall events on people, properties and infrastructure. 

 

Proposed Plan Change 27 has legal effect since Monday, 16 November 2020. This means that all resource and building consent applications, where required, should have regard to the proposed objectives, policies and rules from the date of public notification. However, anyone can submit on the plan change until 5pm on Friday, 18 December 2020.

Tauranga is prone to intense rainfall causing significant amounts of surface water. The city has already experienced the effects of flooding, specifically in 2005 and 2013, when flooding caused damage to properties and put people at risk.

It is expected that the likelihood of flooding will increase over time because of climate change and sea level rise. It is crucial that surface water resulting from rainfall, which can cause flooding of properties and houses, is properly managed to reduce the risk to property and lives.

In addition, Tauranga continues to experience rapid population growth. To cater for the growing population, the city needs to provide more housing capacity. It is essential that development and redevelopment is managed in a manner that reduces the risk to people’s life and property. Plan Change 27 follows the same timeframes as the Housing Choice plan change to ensure that we are not encouraging people to build higher density in unsuitable locations – such as areas likely to be flooded in intense rainfall events.


To understand the risk of flooding, council undertook city-wide risk assessments. These included flood modelling of the likely impacts of a 1% AEP intense rainfall event in Tauranga, taking into account recorded rainfall data and flood levels from past events, the contours of the land and the existing stormwater network. It also factored in the predicted effects of climate change on rainfall and sea level rise out to the year 2130.

The risk assessments identified that Tauranga is at high risk of flooding from intense rainfall. The Bay of Plenty Regional Policy Statement (RPS) requires that the risk is reduced over time. 

Proposed Plan Change 27

The purpose of Plan Change 27 is to ensure that future land use, subdivision and development within Tauranga is planned to be resilient to flooding. The plan change introduces a new rule framework to the Tauranga City Plan to manage the effects of flooding from intense rainfall on people, properties and infrastructure.

The proposed plan change seeks to manage the effects of flooding from intense rainfall by:

  • protecting floodplains and overland flowpaths
  • managing development and redevelopment within flood prone areas
  • managing displacement effects
    • Inappropriate subdivision and earthworks can increase or cause flooding in areas where there was previously minor or no flooding.
  • managing floor levels to reduce damage caused by flooding and risk to life and property
  • managing the cumulative impacts on downstream properties of increased impervious surfaces.

Land use, subdivision and development undertaken within a floodplain, overland flowpath or flood prone area needs to meet the rule framework proposed by this plan change.

Additionally, at the time of development or redevelopment within the Suburban Residential, Large Lot Residential and City Living zones, the impervious surfaces rules also need to be considered.

Plan Change 27 flood maps will replace the current information that council holds on flooding from intense rainfall.

How do I know if I am affected by flooding?

Find flood hazard maps and identify overland flowpaths, floodplains and flood prone areas in any given area in the city.

View maps

What the new rule framework proposes

An overland flowpath is the route taken by water from a rainfall event, making its way downhill towards streams, harbour and coast. Overland flowpaths are a natural occurrence and flow through roads, stormwater reserves and private property. Overland flowpaths are part of the stormwater system and need to be protected in order to reduce the impacts of flooding on people and property. If an overland flowpath is altered or obstructed, the depth and velocity (speed of flow) and volume of the water on site, and on properties upstream and downstream increases.

overland flowpath
Overland flowpath in Mount Maunganui

To maintain the function of overland flowpaths, the plan change proposes:

  • Obstruction of an overland flowpath, including building a fence or wall will require a resource consent.
  • Additions and new buildings in an overland flowpath will require a resource consent.
  • Minor earthworks are permitted, but earthworks above 10m³ and 300mm will require a resource consent.
  • Alteration of a minor overland flowpath on site is permitted as long as water conveyance capacity and entry and exit points from the site are maintained.
  • Avoid new social and cultural and critical buildings in an overland flowpath and restrict additions to these buildings within an overland flowpath.

Floodplains are areas of land situated near a river or stream which are inundated by water during a flood event. They are part of the stormwater system and need to be protected to reduce impacts on people and property. If a floodplain is altered or reduced, the depth and velocity (speed of flow) and volume of the water on site and on properties upstream and downstream increases.

Floodplain normal conditions

Floodplain flood conditions

Floodplain effects of flood conditions

Water storage capacity of a floodplain

To maintain the function of floodplains, the plan change proposes:

  • Obstruction of water, including building a fence or wall will require a resource consent.
  • Additions to existing buildings of up to 20m² in total are permitted.
  • New residential, industrial or business activities within a floodplain require a resource consent.
  • Minor earthworks are permittedy, but earthworks above 10m³ and 300mm in height require a resource consent.
  • Subdivision partially or wholly within a floodplain will consider the protection of these areas as part of a resource consent.
  • Avoid building new social and cultural (e.g. church, schools) and critical buildings (e.g. hospitals) in a floodplain and restrict additions to these buildings within a floodplain. These buildings tend to house more vulnerable people and/or must continue to provide essential services during and after a flood and therefore must be protected from flooding.
     

Flood prone areas are locations where ponding of water occurs in an intense rainfall event. The flow of the water in flood prone areas is much slower than in floodplains and overland flowpaths. Flood prone areas generally occur in areas where there is a depression in the land. Managing activities in flood prone areas includes ensuring safe evacuation from the building in case of a flood, the location of the building in relation to the level of flooding and the type of activity on the land prone to flooding.

Flood prone areas normal

Flood prone areas raised land

How development can displace flood water and increase flood risk.

To manage activities in a flood prone area, the plan change proposes:

  • Minor additions and new builds where the water depth is below 300mm are permitted, subject to floor levels being set above flood level.
  • Additions or new developments where the water depth is 300mm or more will require a resource consent. Water levels above 300mm can be dangerous specially to children and vulnerable adults and can cause trafficability issues (e.g. cause cars to float). New developments need to be designed to ensure the safety of people and damage to neighbouring properties in a flood event is mitigated.
  • Minor earthworks are permitted, but earthworks above 10m³ and 300mm will require a resource consent.
  • Social and cultural and critical buildings should be located outside flood prone areas. Any additions of more than 20m² will require a resource consent.

Pervious surfaces absorb and detain stormwater, reducing runoff from a site. Natural pervious surfaces include grass, landscaped and planted areas. Constructed pervious surfaces generally consist of a layered construction to enable rainwater filtration into the ground, such as living roofs and slatted decks.

As Tauranga continues to grow and develop land, the potential increase in impervious surfaces can lead to increased flooding on downstream properties and put additional pressure on the existing stormwater network.

Impervious surfaces

To manage activities that increase flooding, the plan change proposes:

  • Impervious surfaces of up to 70% are permitted within the Suburban Residential and Large Lot Residential zones. Developments proposing to exceed the 70% threshold require a resource consent.
  • The operative City Plan already controls impervious surfaces in the City Living Zone, permitting a maximum 75% of total site coverage. The existing site coverage rule in the City Living zone is being amended: Where the development proposes to exceed 70% impervious surfaces, it will require a resource consent.

Frequently asked questions

Want more information or have some questions? You may find your answer in the list of FAQs below.

For the purposes of proposed Plan Change 27, an intense rainfall event is a 1-in-100-years rainfall event, taking into account sea level rise and climate change based on the RCP 8.5 median scenario as of the year 2130.

What is a 1% AEP rainfall event?

A 1% AEP rainfall event has a 1% or 1 in 100 chance of occurring in any one year and a 10% chance of occurring in any 10-year period. Similarly, a 1% AEP event can be considered equivalent to the 100-year storm.

Over the next 100 years it is predicted Tauranga, along with the rest of NZ, will experience the effects of climate change, including more intense rainfall events and sea level rise. This will increase the flooding risk within Tauranga which council needs to address.

The Regional Council’s Regional Policy Statement (RPS) sets out the requirements for managing natural hazards in the Bay of Plenty, and every council within the region is required to give effect to it.

The RPS requires Tauranga City Council to plan for flood events of a scale that occur, on average, once every 100 years, considering the effects of projected sea level rise and climate change by 2130. This is considered best planning practice and more and more councils across New Zealand are now planning to this level.

Climate change refers to the changes to the climate associated with the effects of global warming. Climate change is projected to have a significant impact on the land near the coast and harbour, mostly due to sea level rise and the intensification of extreme storm events. 

Information about the global impact of climate change is provided in the Fifth Assessment Report of the United Nation’s Intergovernmental Panel on Climate Change (IPCC). National and regional analysis of climate change impacts have also been carried out by the National Institute of Water and Atmospheric Research (NIWA).

The updated flood maps, which take into account a 1-in-100-years flood event with sea level rise and future climate to 2130 based on the RCP 8.5 median scenario, will supersede related existing flood mapping that Tauranga City Council holds from 16 November 2020.

Updated maps are available at www.tauranga.govt.nz/floodmaps.

To all properties that we identify as being in an overland flowpath, a floodplain or a flood prone area, we will send updated mapping information, details on the proposed plan change and the opportunity to provide feedback on the draft city plan rules.

We are continuously working to improve the information we hold on natural hazards and their effects on our land. Through proposed Plan Change 27 we are updating our flood hazard maps. This updated mapping models the same type of storm event, but it also takes into account sea level rise and future climate change to 2130. This is consistent with the requirements of the Regional Policy Statement.

Along with the updated maps, through Plan Change 27 we are proposing new rules within the Tauranga City Plan to manage land use and subdivision in different type of floodable areas: overland flowpaths, floodplains and flood prone areas.

Once the plan change is formally notified, we are required to make information on flooding available upon request. This includes adding the information on each property’s land information memorandum (LIM) report. If you would like information on any effect this information may have on property value or insurance, we recommend you seek professional advice from a property valuation or insurance expert.

Proposed Plan Change 27 has legal effect since Monday, 16 November 2020. This means that all resource and building consent applications, where required, should have regard to the proposed objectives, policies and rules from the date of public notification. However, anyone can submit on the plan change until 5pm on Friday, 18 December 2020.

The plan change has legal effect, but is not operative. That means anyone can submit on the proposed rules, objectives and policies.

If you are intending to submit a building or resource consent application after 16 November 2020, the application is required to consider the proposed objectives, policies and rules of the proposed plan change.

If you lodged a building consent before 16 November 2020, the proposed plan change rules don’t apply.

Learn more about the City Plan and plan changes

Timeline

  • Early 2019 - October 2020
    Identification of issues and pre-consultation

    Preparation of proposed plan change
  • 16 November - 18 December 2020
    Public notification and submissions
  • Early 2021
    A summary of submissions is published and submitters are invited to make further submissions (10 working days to submit)
  • Mid to late 2021
    Hearings - A hearing committee considers submissions received and will provide recommendations to Council
  • Mid to late 2021
    Decisions - Recommendations are considered at a formal Council meeting and decisions are publicly notified

    Appeals (30 days to lodge)

    Plan change is operative in part of in full depending on appeals

Have your say

Submissions must be lodged in writing by 5pm, Friday 18 December 2020.

Have your say

Alternatively, download the submission form and email or post it back to us.

Submission form (128kb pdf)

Email: city.plan@tauranga.govt.nz

Post to (no stamp required)
Manager: City and Infrastructure Planning
Tauranga City Council
Freepost Authority Nuumber 370
Private Bag 12022
Tauranga 3143

Public open days

Public open days will be held to discuss this proposed plan change. Council staff will be on hand to answer your questions. All welcome!

Find venues and dates

Book a 1:1 meeting at an open day

Book now

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