Project overview

The draft coastal hazard maps identify land that's potentially at risk of flooding (CFHZ) or erosion (CEHZ) by the sea. Time-frames assessed for the mapping include current day (zone 0), as well as 50 years (zone 1), and 100 years (zone 2) into the future. Areas which may already be at risk and those that may eventually be exposed to risk due to coastal processes and potential sea level rise are included in the maps.

The majority of the coastal hazard mapping has been produced by Tonkin + Taylor Ltd. A more refined assessment of coastal flooding in the Awanui, Ruawai, and Northern Wairoa River (including Dargaville) areas has been undertaken by eCoast, based on the same coastal flood hazard levels assessed by Tonkin + Taylor.

The different maps for coastal hazard zones are:

 

Coastal erosion

(CEHZ)

Coastal flooding 

(CFHZ)

Coastal wave run-up

(CRHZ)

Current potential risk areas (2016)

CEHZ 0

(protective structures only)

CFHZ 0

 

Zone 1 – 50-year time frame (2065)

CEHZ 1

CFHZ 1

 

Zone 2 – 100-year time frame (2115)

CEHZ 2

CFHZ 2

CRHZ

Coastal Erosion Hazard Zones (CEHZ)

Erosion zone 0 (Zone 0) – only mapped where erosion protection structures are in place. These represent the extent of likely erosion risk assuming the toe of the foreshore or cliff does not retreat from its current position.

Erosion zone 1 (Zone 1) – these represent the extent of likely erosion risk over a 50 year time-frame (to year 2065) with sea level rise, and where no action is undertaken to prevent erosion of the coast.

Erosion zone 2 (Zone 2) – these represent the extent of potential erosion risk over a 100 year time-frame (to year 2115) with sea level rise, and where no action is undertaken to prevent erosion of the coast.

Coastal Flood Hazard Zones (CFHZ)

Flood zone 0 (Zone 0) – these represent the extent of a 1% AEP[1] coastal storm surge event were it to occur now. 

Flood zone 1 (Zone 1) – these represent the extent of a 2% AEP coastal storm surge event were it to occur in 50 years time (2065) and assuming 0.4m of sea level rise 

Flood zone 2 (Zone 2) - these represent the extent of a 1% AEP coastal storm surge event were it to occur in 100 years’ time (2115) and assuming 1.0m of sea level rise.


[1] AEP: Annual Exceedance Probability is the chance or probability of a natural hazard event (such as a rainfall or flooding event) occurring annually and is usually expressed as a percentage. Bigger events occur less often and will therefore have a lesser annual probability. A 1% AEP event is normally expected to occur on average once in every 100 years, whilst a 2% AEP event is expected to occur once in every 50 years.


Coastal Run-up Hazard Zone (CRHZ)

Coastal wave run-up zone: one zone has been mapped for coastlines exposed to significant wave run-up. This zone is based on the current shoreline, and represents a 1% AEP storm surge and wave run-up event under future sea levels 1m higher than present day. Note that the mapping of the coastal run up hazard zone does not take into account potential shoreline retreat over the next 100 years. Areas located within Coastal Erosion Hazard Zones (CEHZ) referred to above, may become exposed to wave run up as the shoreline migrates landward.

The sites which have been mapped for these assessments are shown below. CFHZ sites are shown in the plan on the left, and CEHZ sites on the right. 

(Open larger versions of these maps in PDF format by clicking on the images.) 

Coastal Flood Hazard Zone sites            Coastal Erosion Hazard Zone sites

Open a larger version of Coastal Flood Hazard Zones Site Locations - PDF format 1.6MB. (Opens in a new window).   Open a larger version of Coastal Erosion Hazard Zones Site Locations - PDF format 270KB. (Opens in a new window).

Identifying areas that could be at future risk of coastal hazards helps regional and district councils as well as land owners to manage the risks associated with new development. Councils are required to help manage risks for land that's susceptible to natural hazards, via national/regional policy, district plans, and building and resource consents. This will also lead to better planning as future development in coastal areas can be located or designed to avoid increasing the long-term exposure to coastal hazards.

Coastal hazard policies and guidance

Two policies outline the legal requirement for the council to provide an assessment of flooding and erosion hazards on our coast – the New Zealand Coastal Policy Statement 2010 and the Regional Policy Statement.

 

New Zealand Coastal Policy Statement 2010

The New Zealand Coastal Policy Statement 2010 is a national policy statement under the Resource Management Act 1991. Objective 5 and Policies 24-27 relate specifically to the management of coastal hazards in New Zealand. In relation to the coastal environment, including coastal hazard areas, council planning documents must give effect to policies in the coastal policy statement.

Read the New Zealand Coastal Policy Statement 2010

Download the New Zealand Coastal Policy Statement 2010 guidance notes on Coastal Hazards (PDF, 2.2MB)

 

Regional Policy Statement

Section 7 of the Regional Policy Statement contains policies on natural hazards for Northland. Policy 7.1.3 relates specifically to coastal hazards, and Policy 7.1.4 deals with existing development in hazard-prone areas.

Find the Regional Policy Statement for Northland

 

Coastal hazards and climate change: A guidance manual for local government in New Zealand

The Ministry for the Environment (MfE) has produced guidance on preparing for climate change that can assist local government decision-making. The guidance on coastal hazards and climate change was updated in 2017 and can be accessed on the web link below.

Find 'Coastal hazards and climate change: Guidance for local government'

 

Specific sea level rise guidance for planning and design in New Zealand is given in section 5.7. Minimum transitional sea level rise allowances for different development types are given in Table 12 of the guidance, shown below:

Table 12 Minimum transitional New Zealand-wide SLR allowances and scenarios for use in planning instruments where a single value is required at local/district scale while in transition towards adaptive pathways planning using the New Zealand-wide SLR scenarios
Category Description Transitional response
A Coastal subdividion, greenfield developments and major new infrastructure Avoid hazard risk by using sea-level rise over more than 100 years and the H+ scenario
B Changes in land use and redevelopment
(intensification)
Adapt to hazards by conducting a risk assessment using the range of scenarios and using the pathways approach
C Land-use planning controls for existing coastal development and assets planning. Use of single values at local/district scale transitional until dynamic adaptive pathways planning is undertaken 1.0 m SLR
D Non-habitable short-lived assets with a
functional need to be at the coast, and either low-consequences or readily adaptable (including services)
0.65 m SLR

The adopted sea level rise allowance of 1.0m to 2115 used to identify Coastal Hazard Zone 2 areas in Northland is therefore suitable for land use planning controls on category C type development shown in this table. The MfE guidance promotes a 10 step dynamic adaptive pathways planning approach for areas potentially affected by coastal hazards.