Dambreak Assessment

The consequences of a dam failure should be understood so that appropriate design, construction, and management actions can be applied to protect people, property and the environment (New Zealand Dam Safety Guidelines, NZSOLD 2015). 

The assessment depends on the judgement of experts in complex areas with acknowledged subjectivity. The steps involve modelling a hypothetical dam breach, assessing the consequences, and assigning a Potential Impact Classification (PIC). The PIC then sets standards for the dam and has implications for design and construction cost, followed by operational costs throughout the lifecycle of a dam.

Tonkin + Taylor has the expertise to provide a sound assessment of PIC, which supports dam owners to efficiently and defensibly manage the potential risks of their dam, canal, or stopbank/levee.  

We undertake dambreak assessments of varying complexity to suit a variety of situations. Dambreak assessment requirements for a small rural irrigation dam may be significantly different to a large hydro-scheme dam with high downstream hazard potential.

We have a proven record in successfully completing peer-reviewed ‘sunny day’ and flood-induced dam break assessments throughout the world.


Our dambreak assessments typically follow the following methodology:

  • Assessment of dam breach potential failure mechanisms, including breach parameters and discharge hydrographs.
  • Use of empirical methodologies or qualitative assessments to identify downstream inundation area and flow characteristics for simple assessments.
  • Quantitative assessment using 1-D or 2-D numerical modelling to map downstream flooding characteristics and inundation areas for more detailed assessments.
  • Identification of populations at risk and incremental damage potential to property, infrastructure and the environment.
  • Recommendation of Potential Impact Classification in accordance with NZSOLD 2015. 

We also provide expert witness evidence for regulatory and Environment Court hearings and peer review services.

We offer other services associated with dambreak assessments including:

Any questions you can email us here: dams@tonkintaylor.co.nz