Natural hazards are addressed by a range of regulatory processes, some of which arise under the Building Act 2004.
The Building Act defines a 'natural hazard' as:
- erosion including coastal erosion, bank erosion, and sheet erosion
- falling debris including soil, rock, snow, and ice
- subsidence
- inundation including flooding, overland flow, storm surge, tidal effects and ponding
- slippage.
Whangarei District Council, as the Building Consent Authority, must refuse to grant a building consent for the construction of a building, or major alterations to a building, under Section 71(1)(a) and (b) of the Building Act if:
- the land is subject to one or more natural hazards, or
- the building work is likely to accelerate, worsen, or result in a natural hazard on that land, or any other property.
However, under Section 71(2) the restriction on the Building Consent Authority's ability to grant a building consent does not apply if:
The Building Consent Authority is satisfied that 'adequate provision' has been made, or will be made, to:
- protect the land, building work, or other property from the natural hazard(s); or
- restore any damage to that land or other property as a result of the building work.
Section 71 of the Building Act 2004
In order to demonstrate that 'adequate provision' has been made for the purposes of Section 71(2)(a) or (b), applicants are required to provide a site specific report from a Chartered Professional Engineer in support of their building consent application.
Council will take that report into account when deciding whether Sections 71(2)(a) or (b) apply.
The report must address Sections 71(2)(a) and/or (b) (as the case may be) and confirm that the applicable statutory requirements will be satisfied, including:
- confirmation that suitable mitigation of the relevant natural hazard has been or will be achieved on site;
- confirmation that the proposed design incorporates appropriate protection of the land, the building work, or other property and / or that any damage to the land or other property will be restored;
- Producer Statement (PS1) certification of the design;
- assessment of compliance with the NZ Building Code.
Despite the requirements of Section 71, there are instances when the Building Consent Authority must grant a building consent for building work on land subject to natural hazards.
The criteria are set out in Section 72 of the Building Act. They are:
- the proposed building work will not accelerate, worsen, or result in a natural hazard on the land on which the building work is to be carried out or on any other property; and
- the land is subject to, or is likely to be subject to, one or more natural hazards; and
- it is reasonable to grant a waiver or modification of the building code in respect of the natural hazard (if required).
Section 72 of the Building Act 2004
These criteria must be satisfied before section 72 will operate to avoid the restriction on a Building Consent Authority's ability to grant a building consent that arises under section 71(1).
If the Building Consent Authority determines that a natural hazard is present and affects the land on which the building is to be situated but this is not likely to worsen the hazard as section 72 then the Building Consent can be issued.
However, a condition will be placed on the Building Consent stating what the natural Hazard(s) is and the hazard(s) will be included on the certificate of title (section 74). The Building Consent Authority will usually contact the owner/applicant to inform prior of any decision to add a natural hazard condition to the consent.
The owner may make and application for a determination on this decision following the Ministry’s determinations process
Determinations (Ministry of Business, Innovation and Employment website)
If your proposed building work is in an area affected by these soils, you will have to show in your application how you are going to mitigate this feature.
If officers cannot be satisfied on reasonable grounds that this mitigation is in place, consent will not be issued.
The Building Code Clause F1 Hazardous agents on site, sets out the minimum performance criteria when dealing with this type of site and details investigation methods and possible remedial actions that may be required.
F1 Hazardous Agents on Site
Acid Sulphate Soil Planning Policy
The Whangārei District has a history of mining and has known mining hazard areas of land that are subject to subsidence due to past mining activities.
These areas have been incorporated into the District Plan rules and require, at least, a site specific geotechnical survey of the ground under and in the immediate vicinity of any proposed building work.
Council will, in these cases, on application for building consent, have the required geotechnical report peer reviewed by another competent geotechnical engineer to ensure that suitable consideration and conclusions are present.
This will incur an extra cost for the application. This is necessary to ensure satisfaction on reasonable grounds that building work will not be affected by previous mining activities or subsidence.
On 31 May 2023 Council notified Plan Change 1 – Natural Hazards introducing new provisions to manage subdivision, land use, buildings, major structures and earthworks in mining hazard areas identified on District Plan maps. In addition, some minor changes are proposed to mining subsidence hazard mapping in Hikurangi.
For further information about this proposed plan change, please view the Plan Change consultation page below:
Plan Change 1 - Natural Hazards
Please refer to Natural Hazards information under My property and rates and / or the Natural Hazards Chapter of the District Plan.
Natural hazards
District Plan