The District Plan, under NZS4404:2010, determines the building platform level through the combination of two components:
- The 1% Annual Exceedance Probability (AEP) flood level; plus
- Freeboard.
The 1% AEP is determined by either the Bay of Plenty Regional Council or the Whakatāne District Council as outlined below.
The amount of freeboard to be added is determined under the District Plan. Please contact the Resource Consents Planning Team (Duty.Planner@whakatane.govt.nz) to advise the freeboard amount.
You will need to provide the 1% AEP advice to allow the freeboard level to be determined.
Annual Exceedance Probability (AEP) Flood Level
The AEP is the chance or probability of a natural event (such as a flood flow) of a particular size or greater occurring in a single year. A 1% AEP flood flow has a 1%, or 1-in-100 chance of occurring in any one year.
Within Whakatāne Urban Area
Within the Whakatāne township, the 1% AEP flood level for each property is determined by the Whakatāne District Council (WDC).
Applicants must obtain an email from WDC confirming the applicable AEP flood level and this email must be submitted with the building consent/resource consent application. The email must be issued within 6 months of the date of application.
Request a 1% AEP level (Flood Level Report) online »
Outside Whakatāne Urban Area
For all areas outside of Whakatāne township (i.e., all rural areas, Edgecumbe, Tāneatua, Awakeri, and all coastal areas), the 1% AEP flood level for each property is determined by the Bay of Plenty Regional Council (BOPRC).
Applicants must obtain a letter from BOPRC confirming the applicable AEP level and this letter must be submitted with the building consent/resource consent application. The letter must be issued within 6 months of the date of application.
Request a 1% AEP flood level from BOPRC online »
Freeboard
The term Freeboard is specifically defined in NZS4404:2010 as:
"A provision for the flood level design estimate imprecision, construction tolerances and natural phenomena (such as waves, debris, aggradations, channel transition, and bend effects) not explicitly included in the calculations".
Table 3 in NZS4404:2010 specifies the minimum freeboard to be applied depending on the type and use of the building as follows:
| Type of Structure | Freeboard height above design inundation level |
|---|---|
| Habitable dwellings (including attached garages) | 0.5m |
| Commercial and industrial buildings | 0.3m |
| Major community facilities related to supply of electricity, telecommunications, water supply or wastewater disposal. | 0.6m |
Practical Design and Construction of the Minimum Building Platform
Having determined both the 1% AEP level and any freeboard to be added, the building platform can be designed to achieve at least this level.
Figure 1 shows how the building platform level shall be designed and constructed based on the type of building foundation.
Figure 1: Whakatane District Plan Rule 18.2.3.2- Determining Building Platform Levels and Freeboard:
Resource Consent and Building Consent
If a proposal meets the required minimum platform level (and meets all other rules in the District Plan), then no resource consent is required.
If a proposal does not meet the minimum platform level, then resource consent will be required. The resource consent can be granted, with or without conditions, or refused.
It is recommended that an applicant discusses their proposal with an Environmental Planner at the Whakatāne District Council before preparing a resource consent application for a development that does not achieve the minimum platform level. A resource consent application will need to be supported by specialist engineering advice.
The Building Act 2004 and Building Code also apply to the construction of buildings. Regardless of any resource consent decision, a building must still be designed to achieve Clause E1 (Surface Water) of the Building Code.
If the land to which the building consent application relates is subject to natural hazard(s) then the building consent will be issued subject to Sections 72-74 of the Building Act. This applies regardless of whether or not the specific building proposal meets the minimum platform level.
Resource Consent Considerations and Possible Conditions
In some cases, a lower minimum platform level may be approved through the grant of resource consent. This approval will be made based on the objectives, policies and assessment criteria in the Whakatāne District Plan, consideration of other Regional and National planning documents and the actual and potential effects of the proposal, including any proposed mitigation measures.
Appropriate mitigation may include the materials proposed to be used in the building and their ability to withstand damage from inundation, the proposed height of electrical fittings and services and/or the proposed use of the building.
Land covenants may be used in some cases to ensure all future owners are aware of the nature of the hazard(s) and risks to the site and buildings.
Subdivision Consent
Depending on the timing of the provision of a building platform, a:
- condition, or
- consent notice clause, and/or
- advice note relating to provision of a building platform and compliance with Rule 18.2.3.2
will be added to any subdivision consent.
For example, when a building platform for a dwelling is required to be formed prior to the issue of a Certificate of Title, the following condition would be imposed:
"Each lot shall be provided with a building platform that achieves a minimum level equivalent to the 1% AEP flood level plus 500mm freeboard (measured in Vertical Datum)."
If the building platform is not to be determined until the time of construction after the issue of a Certificate of Title, the following clause could be imposed as part of a consent notice registered on the Record of Title:
"Ensure that any habitable building constructed on the lot is constructed with a minimum platform level equal to or above the 1% AEP flood level plus 500mm freeboard (measured in Vertical Datum). The 1% AEP level shall be determined by the Whakatāne District Council [or Bay of Plenty Regional Council] at the time of Building Consent application.
Vertical datum
We now use New Zealand Vertical Datum (NZVD2016) to measure height information. This new datum ensures consistency around how land height is measured across the district, and aligns with New Zealand standards.
Find out more about the New Zealand Vertical Datum »
Conclusion
The minimum building platform is determined by adding the 1% Annual Exceedance Probability (AEP) flood level and any applicable freeboard specified in NZS4404:2010.
The practical design and construction of the platform level is dependent on the foundation design and must be in accordance with Figure 1 above.
If a building proposal (including extensions to existing habitable buildings) cannot meet the minimum platform level requirement, resource consent is required.
All buildings must also comply with the Building Code.