Dams - Construction, Alterations and Safety Regulations

Construction or Alterations of Large Dams 

If you are an owner of a large dam or canal, or you're planning to construct, modify or remove a dam, canal or structure associated with a dam, you'll need to consider whether you need a building consent before you begin work.
‘Large dam’ means a dam that has a height of 4 or more metres and holds 20,000 or more cubic metres volume of water or other fluid as set out in the Building Act 2004.  If it is not a large dam it doesn’t require a building consent but it must be constructed to meet the Building Code.

If you are an owner of an existing dam, you have until 13 May 2024 to prepare for your dam safety responsibilities under the new Building (Dam Safety) Regulations which are requirements to ensure dams are maintained and inspected after being built. For more information refer to the Building (Dam Safety) Regulations 2022 section below. 
Potentially there are two types of consents that may be required to build /alter a large dam which are resource consents and/or building consent. It is possible, depending upon the size of the proposed dam and its location, that it may require only one of the above, possibly both of the above or even none of the above. 
For information on resource consents please email our Consents team on consents.enquiries@horizons.govt.nz or call our Horizons Duty Planner on Freephone 0508 800 800. Alternatively you can find more information here. 
Horizons is responsible for dam activities within the Region, and our Coordinator District Advice is available to assist with building consent applications and dam safety regulations. For more information on this service, please see our dams factsheet below.

Read our Dams factsheet (1.5MB PDF)

Building (Dam Safety) Regulations 2022

As expected, the Ministry of Business, Innovation and Employment (MBIE) recently announced new regulations around dam safety. The regulations take effect from 13 May 2024, giving dam owners two years to prepare for their dam safety responsibilities.

The regulations aim to protect people, property and the environment from the potential impacts of dam failures and set a minimum requirement for dam safety. They also promote regular monitoring and surveillance practices, as dam owners will be responsible for maintaining them to acceptable safety levels.

Detailed information and resources to support dam owners, technical practitioners and regional authorities with their responsibilities are available on MBIE’s website.

MBIE have produced a helpful dam safety guidance document which Horizons District Advice highly recommend you read.

Dam safety frequently asked questions are available on Waikato Regional Council's website.

Dam Safety Regulations - Dam Size

Please note that the dam safety regulation size is different to the “large dam” criteria for building consents.  This large dam information for building consents can be found on our dams factsheet.

Dangerous Dams Policy

The Building Act 2004 introduced legislation for managing the safety of existing and new dams in New Zealand. Under this Act, regional councils must have a policy on how they will deal with dangerous dams, earthquake-prone dams and flood-prone dams in their region. 


The Manawatū-Whanganui Region has a number of large dams that are used for a variety of purposes including hydroelectric generation, water supply, flood control, irrigation, farm stock supply and recreation. This policy was developed to help reduce the risk of dam failure in Manawatū-Whanganui Region.


Dam owners have the primary responsibility for identifying, monitoring and reporting on dangerous, earthquake-prone and flood-prone dams and for reducing or removing the risk of harm to people, property and the environment in a timely and effective manner.


An engineer engaged (by the owner) will notify the Council and the owner of the dam if he or she or they believe that the dam is dangerous.


This policy will be reviewed as part of the new dam safety regulation implementation.

View a copy of the Dangerous Dams Policy here.

Questions and Enquiries

If you have any dam related questions, contact our District Advice team via our online enquiry form.

Tips for completing the online form:


  • Search by property address or valuation number (e.g. 11 Victoria Avenue or 12345 678 00). 
  • Exclude the town/city in the search field as the database searches by district.
  • For rural addresses without road numbers, enter the property by valuation number (remember to tick the valuation number box on the form).
  • Find property details and valuation numbers via the District Advice map in our online map gallery. Search for the property by street address, title, or valuation number, or navigate the map manually. You can also find property information via our online Rates Search tool.
  • If you need help submitting the form, please email us at district.advice@horizons.govt.nz.