Hawke's Bay Regional Council: Flood Scheme Review

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In the devastating aftermath of Cyclone Gabrielle in February 2023, Hawke’s Bay Regional Council had to undertake urgent resilience planning. 

The council’s stopbanks, pump stations, spillways and floodgates were designed for a pre-Gabrielle world. The flooding had also damaged infrastructure, changed the course of rivers, and reshaped the landscape. The council urgently needed updated modelling of its major flood control schemes, like the Heretaunga Plains, to make informed decisions about land use, infrastructure and funds to protect its communities.

The reviews had been planned to take place over the next 10 years, but the Council decided to complete the reviews in just 12 months to align with community expectations. The volume of work was significant, so using external consultants would allow the internal team to concentrate on additional post cyclone work. The council engaged four of New Zealand’s top engineering firms to conduct the scheme reviews. 

But as the council’s Principal Engineer Craig Goodier explains, that came with its own problems. 

“Each firm had different approaches and methodologies, which on its own may not be a problem, but we wanted the consultants to deliver similar modelling outputs including file formats and model setups. Without this consistency, the result would have been extra work for us.”

To demonstrate alignment with HBRC’s needs and provide a crucial peer review, Craig turned to the team at Submergent. They came with a reputation for thoroughness, which Craig says wasn’t misplaced. 

“I knew they were the people for us. You don’t want anyone thinking, ‘Oh, this will be good enough….’ Submergent staff are sticklers – in a good way.”

Submergent steps in to help the Council set the standard 

Submergent worked with HBRC to define clear purposes, objectives and success criteria for each scheme. The team could then lead a comprehensive peer review of the flood models built by some of NZ’s largest engineering firms. Submergent created a review framework to manage the idiosyncrasies and work through the firms’ different approaches. This ensured the models delivered consistent outcomes and would meet the council’s immediate needs. 

“We can get Carl and Rathika to peer review all the work and have confidence in the results,” says Craig. “They were great – so much so that I could continue with other tasks, knowing they’d do it right.”

The team used a project-wide view to identify issues early, then communicated and promoted solutions to council staff at regular meetings. Although HBRC was less familiar with TUFLOW flood modelling software, Submergent’s involvement in this project gave the council added confidence that the models were up to scratch.

Experience you can’t shortcut

Craig says Submergent’s specialist knowledge proved invaluable. 

“They found some modellers using techniques that wouldn’t deliver the required accuracy. You only get that kind of understanding after years of trial and error – you can’t shortcut it.” 

When the Submergent team found an issue with the models or results, they could quickly see why it had happened, how to solve it, and if it was important. 

“They’re excellent at documentation, with a good spreadsheet showing what the issue was, the solution, and whether it needed to be fixed or was cosmetic.”

Future-proofing council modelling

Submergent went beyond peer review, suggesting a way to set up the file structure so the council will continue getting value from the models into the future. 

“That was something Submergent offered and I knew it would be very helpful. The consultants are now in the process of giving us the models so we can use and run them ourselves. The setup and file structures are all consistent and easy to understand.”

An experienced engineer, Craig knows expertise when he sees it and was impressed with the care the team took. 

“It’s not just about the result – it’s about how usable it is. There’s a bit of artistry to it. Modellers might get the same result, but one model takes three days to run and the other only three hours. Submergent is into that finesse. Submergent would be great at instructing modellers looking to improve their skills.”

Global expertise, local connection

Craig believes Submergent’s expertise makes it stand out in the market – and puts it on the world stage. 

“Submergent would never say, ‘It’s good enough,’ and that’s an important part of its reputation. While you can access similar experiences with international firms, the time difference often makes projects difficult to schedule. Sometimes the people doing the modelling are overseas, so it’s three in the morning when you need them. With Carl and Rathika, they’re local, and you can just talk to them to avoid unnecessary delay.”

Clarity from complexity 

With Submergent’s meticulous oversight, Hawke’s Bay Regional Council added coordination and quality control to what could have been a chaotic and rushed process. By aligning the consultants’ methodologies, the team uncovered and documented the modelling process with clarity and precision, helping council staff deliver consistent results for the ratepayers.

Submergent’s mix of technical depth, practical thinking and collaborative finesse gave HBRC what it needed most after Cyclone Gabrielle: clarity, consistency, and results delivered in tight deadlines. 

“I’d recommend them – absolutely” says Craig. “I only have positive things to say. They’re knowledgeable, thorough, approachable, easy to talk to and helpful.” 

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