What you need to know about dams and consents

A dam is defined in the Building Act 2004 (section 7) as an artificial barrier and its appurtenant structures that are constructed to hold back water or other fluids to form a reservoir that is used for storage, control or diversion of that water or fluid.  

It includes:

1. A flood control dam
2. A natural feature that has been modified to function as a dam
3. A canal
4. Stormwater detention dams
5. Dams associated with roading.

It excludes:

1. Stopbanks designed to control floodwaters

Examples of other fluid are effluent, tailings from mining operations or other industrial waste in a liquid form.

A large dam is defined in the Building Act 2004 (section 7) as a dam that has a height of 4 metres of more and stores 20,000 or more cubic metres volume of water or other fluid.

How to measure the height of a dam is defined within the Building Act 2004 (section 133B).  The height is the vertical distance from the crest of the dam and must be measured, as follows:

• Dams across streams, the height is measured from the natural bed of the stream at the lowest downstream outside limit of the dam
• Dams not across streams, the height is measured from the lowest elevation at the outside limit of the dam
• Canals, the height is measured from the invert of the canal.

Stored volume of a dam is defined within the Building (Dam Safety) Regulations 2022 (section 7). It sets out what is not included in the stored volume of water or other fluids. This is the current definition of stored volume from the Ministry of Business, Innovation and Employment (MBIE) and aligns with the Dam Safety requirements for large dams. The dam’s stored volume does not include:

• Water or fluid that is lower than the natural ground level at the lowest downstream outside limit of the dam for dams that are across a stream
• Water or fluid that is lower than the natural ground level at the lowest elevation at the outside limit of the dam for dams not across a stream
• Water or fluid that is lower than the natural ground level at the lowest elevation at the outside limit of the canal structure for canals where the canal invert is below natural ground level.

More information on measuring dams can be found below.

An appurtenant structure is defined in the Building Act 2004 (section 7) as a structure that is integral to the safe functioning of the dam as a structure for retaining water or other fluid.

Examples of appurtenant structures to dams are spillways, penstocks, intake towers and outlet tunnels.

A building consent is an approval from a Building Consent Authority (BCA) to undertake specific building work in accordance with approved plans and specifications on a particular site.  This approval ensures that the proposed work complies with the current Building Act and its relevant regulations (e.g. Building Code) which will see the construction of safe and durable buildings that do not endanger the health or safety of building users.

A building consent is not a resource consent.  These are applications that are required to carry out construction under different pieces of legislation.  Having one does not give approval for construction under the other legislation.  You will need to check both the Building Act and Resource Management Act to ensure all consents have been obtained before you begin works on site.

NOTE: A building consent can only be obtained from an accredited and registered BCA, who are authorised to process your application for building consent, inspect the building works and certifying your building on completion. 

As per the requirements of Section 14 in the Building Act 2004, Regional Authorities are responsible for performing functions under the Building Act relating to a building that is a dam.

Waikato Regional Council is an accredited Building Consent Authority (BCA) to undertake building consent functions (including code compliance certificates) for dams only.  We are accredited by International Accreditation New Zealand (IANZ) and registered as a BCA with the Ministry of Business, Innovation and Employment (MBIE).  

Any building consent application for buildings that do not meet the definition of a dam within the Building Act 2004 cannot be accepted by WRC and must be submitted with the local Territorial Authority.  

Waikato Regional Council currently undertake Building Consent Authority (BCA) work for a number of regional councils within the North Island. The councils which we currently hold the BCA powers to undertake building consenting for dams under the Building Act 2004 are:

• Northland Regional Council
• Auckland Council
• Bay of Plenty Regional Council
• Hawkes Bay Regional Council
• Taranaki Regional Council
• Horizon’s Regional Council
• Greater Wellington Regional Council

This collective has been in place since 2008 and prevents the duplication of services and provides efficiencies for all councils involved to ensure that dams constructed within our regions are built well and minimise potential risks to people and property.

This agreement does not include the works required under the Building (Dam Safety) Regulation 2022 in which all regional and local councils are responsible as the authority for their region.  

Resource consents are often required for dams as they involve the taking, using, damming and diverting of water and controlling of the quantity, level and flow of water. Also, the works associated with the dam construction itself can often trigger the requirement for resource consent.

To determine if you require resource consent, we recommend you contact us or your local council.

Information on the Resource Management (National Environment Standards for Freshwater) Regulations 2020 can be found below.

No. A dam is not considered Restricted Building Works under the Building Act 2004. Restricted Building Works are works carried out in association with residential dwellings and do not include non-habitable structures.

More information on restricted building work can be found below.