Upgrades of Wellington Airport sea defences

WRL completed 2D and 3D physical modelling to assess the complex coastal processes, optimise and validate the proposed upgrades.

Close up of the Cubipods used in the 3D wave basin physical model for the upgrades of Wellington Airport sea defences

Year: 2025
Client: Beca

Wellington Airport is in Lyall Bay at the southern side of Wellington, New Zealand. Existing seawalls that were built 50–70 years ago, have reached the end of their natural lifespan and require an upgrade to protect critical infrastructure from erosion and sea level rise.

A robust design is needed, as the site is exposed and has an energetic wave climate. Our physical modelling study area focused on the end of the runway.

A combination of 2D and 3D modelling was used to assess the complex coastal processes, optimise and validate the proposed design: 

  1. 2D physical modelling (1:37.5 scale) of a representative cross-section of the proposed bund wall to investigate structure design, overtopping and armour stability.
  2. 3D physical modelling (1:60 scale) of Lyall Bay with outer reefs and the full extent of the upgraded Southern Seawall to provide assessment of the armour stability under design wave loading.

A model of the existing Southern Seawall using Akmons was first constructed in the wave flume, to provide a realistic foundation for the proposed upgraded Cubipod® revetment, and to determine an existing structure performance baseline.

This physical model is the largest built at WRL to date, with over 5,000 individual blocks all hand-placed! 

Once constructed, it will be the first use of Cubipods® in the Southern Hemisphere.
Dr Tommy Fellowes with the 3D wave basin model for the upgrades of Wellington Airport sea defences Toby Tucker, UNSW Water Research Laboratory

Testing was conducted on two separate revetment upgrade options, to optimise structure performance and reduce its footprint, saving money and CO2 emissions.

The preferred upgrade for the Southern Seawall involves placing new concrete armour 15.5t Cubipods® units over the existing Akmons and rock infill, following reprofiling to a uniform slope. Cubipods® showed self-repairing capability when unit loss remained minimal.

Design optimisation from the physical modelling led to:

  • 12% reduction in unit count with a combined single and double-layer design.
  • Narrower crest and single-layer design in less exposed areas.
  • Recurve crest wall addition improved overtopping performance by up to 90% for extreme wave events.

For further information contact:

Dr Francois Flocard | Director, Industry Research | f.flocard@wrl.unsw.edu.au