Hawke’s Bay Stopbank and Flood Protection

Overview

Following Cyclone Gabrielle in February 2023, widespread flooding caused extensive damage to the stopbank and flood protection network across the Heretaunga Plains. Significant breaches, such as the Maraenui Golf Course, left nearby residential areas like Te Awa exposed to further risk. LDE moved from voluntary emergency response to providing urgent technical support alongside HBRC to stabilise and rebuild critical sections of the stopbank and flood protection system.

What we did

Within a week, LDE was on site overseeing emergency remediation works at two key breach locations at Maraenui. These sites presented challenging conditions, including restricted access, saturated ground, and material supply constraints. Notable challenges and solutions included:

• Use of stabilised lime backfill to enable effective compaction despite excess moisture
• Geogrid reinforcement at Breach 02  to improve structural integrity and reduce long-term settlement
• Precise machinery operation in confined, muddy conditions
• Rapid redesigns in response to unexpected site setbacks, including equipment bogging and a recovery that disturbed the site further

Despite these challenges, both breaches were successfully remediated within one month, reinstating emergency flood protection to the lower Heretaunga Plains with a ‘like for like’ basis. Post-construction analyses confirmed the repairs met 1-in-100-year design standards and were suitable for retention as part of any global network upgrade strategy.

We then supported further works at Dartmoor Upper and Lower, introducing LDE’s ‘pod’ system to streamline construction oversight and reporting. Material testing and placement strategies were refined, cohesive fill for stopbank cores, gravel shoulders for drainage, verified in progress to ensure global stability and future performance.

Later phases included:

• Springfield Lower (Jul–Sep) – major winter repair works and shoulder remediation
• Ohiti Stopbank (Nov–Dec) – careful benching and restoration completed ahead of the next cyclone season

Throughout, LDE maintained close coordination with HBRC, adapting designs and methods to site conditions and maintaining momentum under pressure.

Outcome

LDE delivered fast, practical and durable solutions to reinstate critical flood defences across the Heretaunga Plains. Repairs were completed to design standards, with long-term integration into HBRC’s wider network strategy.

Despite entering with no prior stopbank-specific experience, LDE’s civil and geotechnical team applied sound engineering judgment, quickly developed tailored approaches, and gained valuable expertise in stopbank design, material behaviour, and flood resilience construction.

LDE is proud to have played a key role in rebuilding flood protection infrastructure across the Heretaunga Plains, contributing to the region’s resilience and future preparedness. We now carry forward specialised experience in stopbank design and construction for future infrastructure recovery and resilience projects.