ANCOLD 2024 Conference Adelaide
In February 2023 the Hawke’s Bay Region, located on the East Coast of New Zealand’s North
Island, was severely impacted by Cyclone Gabrielle. Flooding resulted in approximately thirty
levee breaches with flood depths to about 7 m and sediment deposits to house roof line in some
areas.
Other consequences across the region included eight deaths and many billions of dollars damage.
Example losses included many houses written off, damage to infrastructure including major road
bridges destroyed, loss of levees, the Redclyffe electrical substation, rail lines, as well as damage
to horticulture and other businesses. In select locations future land use changes will be implemented
because of the event.
To set the scene, the paper will overview hydrological aspects of the event. Flood defence
infrastructure performance and the impact on levees from an extreme event that was well beyond
original designer expectations (overdesign event performance) is discussed, as is embankment
response to overtopping flows. Forensic assessment on how materials performance failure
mechanisms occurred is provided.
