FAQs

The Dangerous Dams Policy outlines how Environment Southland will identify and manage dams that may pose a risk to people, property, or the environment. It covers dangerous, earthquake-prone, and flood-prone dams, and sets out how we’ll work with dam owners to reduce or remove those risks.

Under the Building Act 2004, regional councils must have a policy in place for managing dam safety. Environment Southland has not previously had a specific policy, so we are now developing one to meet legal requirements and improve public safety.

A dam is considered dangerous if:

• It has the potential to cause medium or high impact if it fails (for example, damage to homes, roads, or the environment).
• It is likely to fail:
  • During normal conditions (without any unusual event),
  • In a moderate earthquake, or
  • In a moderate flood.

Earthquake-prone dam

A dam is considered earthquake-prone if:

• It has a medium or high potential impact, and
• It is likely to fail in a significant earthquake (called an “earthquake threshold event” in the regulations).

Flood-prone dam

A dam is considered flood-prone if:

• It has a medium or high potential impact, and
• It is likely to fail in a significant flood (called a “flood threshold event” in the regulations).

Want to read the official definitions?

You can find the full legal definitions here:

• Section 153 and 153A of the Building Act 2004
• Regulation 19 of the Building (Dam Safety) Regulations 2022

Dam owners are primarily responsible for identifying, monitoring, and managing risks associated with their dams. Environment Southland supports this by maintaining a register of classifiable dams and ensuring dam safety information is shared with relevant authorities.

Only a small number of dams in Southland meet the criteria for this policy. Most are used for agriculture, flood protection, or hydroelectric purposes.

Southland’s dams are exposed to risks such as:

• Heavy rainfall and river flooding (e.g., Mataura, Ōreti, Aparima, Waiau catchments)
• Seismic activity near the Fiordland Fault System

We’ll review all feedback, host a hearing if needed, and may make changes to the draft policy. The final version will be adopted by Council and published on our website.