Hawke’s Bay, 24 July 2024 – The report of the independent Review into the circumstances and contributing factors that led to flooding in the wake of Cyclone Gabrielle has today been presented to Hawke’s Bay Regional Council.

The independent panel (Dr Phil Mitchell Chair, Kyle Christensen and Bernadette Roka Arapere) thanked the public for their contributions to the Review.

The panel acknowledges everyone who participated; we sincerely thank them for their valuable input, and invite anyone with an interest in the Review to read the report online at www.hbifr.nz.

Cyclone Gabrielle caused one of the largest flood events in New Zealand’s history which overwhelmed structural flood defences (stopbanks), inundating unprotected floodplains across the entire region. The flood caused destruction and devastation to families, communities, businesses, infrastructure, whenua and taonga.

“The lack of planning and preparedness for events exceeding the capacity of stopbank systems was also apparent in the many unprotected floodplains of the region. Flood risk had been underestimated in a number of locations because large historic floods had not been included in the analysis of flood size, and there was limited detail or wider understanding of trigger levels and likely areas of inundation for warnings and evacuations to be effective.

“There was residual risk to the entire Heretaunga floodplain, including the densely populated urban areas of Taradale, Hastings and Napier. It meant that more than 100,000 people were at risk, owing to there being no practical solution for evacuations prior to a flood arriving.”

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In the lead up to and during any heavy rain event, one of the most critical activities HBRC undertakes is to provide accurate and timely flood forecasting and advice to territorial authorities and Civil Defence so they can provide warnings to communities and initiate evacuations when required. This involves HBRC using a combination of their own flood hazard mapping and real-time river level monitoring systems together with MetService rainfall forecasts.

The significant difference between forecast and actual rainfall, the failure of the repeater supporting some of HBRC’s telemetry system, the loss of, and damage to, some water level and rainfall measuring equipment, and staff being overwhelmed by the sheer scale of the event meant there were many challenges for HBRC in providing accurate and timely flood forecasts and advice to Civil Defence.

“The cost of rebuilding and improving flood management infrastructure is likely to be unaffordable if soley funded by local communities. A shift back to central government partially funding these works is likely to be needed to achieve effective long term solutions.

“Genuine collaboration and partnership is needed between local and central government and communities, mana whenua and businesses to evaluate and progress options for better managing flood risk in the future.

“We are satisfied that the key issues have been identified and that this review provides a road map for the future that sets out the lessons that HBRC and the community can employ to improve the region’s resilience to flooding in the future,” the panel concluded.

The Hawke’s Bay Independent Flood Review makes 47 recommendations across seven key areas to improve flood resilience:

Key areas of focus:

• Structural works (14 recommendations)

• Flood event management (7 recommendations)

• Planning controls (8 recommendations)

• River channel maintenance (6 recommendations)

• Mana whenua (6 recommendations)

• Community (3 recommendations)

• HBRC Resourcing and funding (3 recommendations)

Structural works

Kyle Christensen says that legacy flood management infrastructure developed through the past century is, in many places, no longer fit for purpose.

“It needs to be substantially upgraded and re-imagined to provide a safe, healthy and resilient river, floodplain and overall catchment system.

“Any new stopbanks need to be designed in a way that provides predictable and manageable performance during events that exceed their capacity.

“The key strategic arrangement of the catchment system needs to be based around the evolving global best practice of “Making Room for the River” and “Natural/Nature Based Solutions”, with the overarching objective to safely convey very large floods from the upstream end of the floodplains to the sea.

“This type of design is a step-change from current practices and involves a far higher level of sophistication in the conceptual arrangement of the system. Fundamental to this is designing the system so that its performance in super design events is known, not left to chance - which is a feature of many of the current systems,” says Mr Christensen.

Flood event management

Kyle Christensen says the magnitude of this flood significantly exceeded the capacity of stopbank systems with numerous breaches causing significant inundation of the floodplains.

“The design of the stopbank system directly relates to how and where it will fail in a super design event (like Cyclone Gabrielle).

“If super design events haven’t been incorporated into the design with spillways, overflows and known failure points, then you cannot readily determine where floodwaters will go during a super design event.

“The fact that there was no event management plan for the Heretaunga Plains was a result of there being no way of predicting where overflows would go, and no practical way of evacuating all of the 100,000 people possibly affected from the entire area.”

Considering areas where there were no stopbanks and known flood risk (North Clyde, Tangoio, Esk Valley and Pōrangahau) the level of pre-event planning was very limited, as evidenced by the HBRC flood manuals, and advice through the event appeared adhoc with a lack of clarity on what was actually being predicted. The accuracy of advice was also significantly hindered by under-forecasting of rainfall from MetService, as well as a repeater failure and the loss of some rainfall and river flow monitoring sites, affecting the ability of HBRC to accurately forecast flood flows.

“As already highlighted for the Esk and Pōrangahau floodplains, the significant flood events of the past 100 years were not included in the flood frequency analysis and flood risk mapping, and as such the understanding of the depth and extent of possible flood inundation was likely underestimated,” says Mr Christensen.

Planning controls

The Regional Policy Statement which is HBRC’s main tool for influencing land use did not provide definitive direction to territorial authorities on how their district plans should identify and manage flood hazard risks, says Dr Phil Mitchell.

“The fact that there were relatively new housing developments in areas of known flood risk suggests that lessons from the past have not been learnt, and development has been allowed in high hazard areas.”

Residential developments have been allowed to occur in locations such as the Esk Valley and Tangoio despite a well-documented history of significant flooding. Such areas are considered unsafe for residential use and are now within the Category 3 classification. Similar declarations were made by local authorities following the 1938 Esk Valley Flood and the 1963 Tangoio Flood.

“Weak and insufficient planning direction has enabled poor planning decisions, and shows just how short society’s memory is when it comes to matters of flood hazard management,” he says.

Among HBRC’s responsibilities under the Resource Management Act is the responsibility to prepare, implement and review a Regional Policy Statement (RPS).

“Large parts of the RPS including the natural hazards chapter have not been reviewed since the RRMP (Regional Resource Management Plan) was made operative in 2006. Key policies for flood hazard management are weak and too vague, leaving wide-ranging discretion for land use management in the various district plans.

“HBRC should urgently review the Regional Policy Statement so it includes clear and direct objectives and policies regarding land use management in flood hazard areas; ensure the Council has sufficient financial and people resources available to provide effective advocacy and technical input to planning processes and resource consent applications, so that development does not occur in areas subject to unacceptable flood hazard risk, and review current resource consents in terms of the risk to flood management activities,” says Dr Mitchell.

River channel maintenance

Due to the extreme nature of the Cyclone Gabrielle flood event, the panel concludes the level of maintenance would have likely had a limited impact on the consequences of the flood event. The panel noted a number of areas where more maintenance could have been undertaken in terms of willow clearing and gravel extraction.

Key recommendations include re-surveying all river and stream channels and returning the systems to the agreed level of service, being more proactive in managing gravel build up, and being more directive about where gravel is removed from, investigating options for permanent river mouth openings, and evaluating the need for adding maintenance of the Wairoa River channel within the scope of the asset management plan for the area.

Mana whenua

The panel considers that mana whenua were disproportionately impacted by the flood, says Bernadette Roka Arapere.

There are several examples throughout the region of marae, papakāinga, and urupā being located on marginal floodplain land in close proximity to rivers, that were catastrophically inundated during the flood.

The typical pattern the panel observed was that land currently occupied by Māori communities is the remnant of much larger holdings they held prior to pākehā occupation.

“In many places there was known flood risk at these floodplain locations, and no structural flood defences or planning to provide management of that flood risk.

“We received feedback of a disconnect between some mana whenua groups and HBRC, and a perception that HBRC does not protect mana whenua communities in the same way that other communities are protected against flood risk.

“HBRC should recognise and provide for Māori communities and lower socio economic areas that are disproportionately exposed to flood risk, because flood protection of those areas does not satisfy HBRC traditional cost/ benefit approaches.

“The panel considers that more needs to be done to work with mana whenua at a governance level; that inequities between mana whenua and other Hawke’s Bay communities need to be acknowledged by HBRC, and a new flood management model needs to be developed with mana whenua for a safe and sustainable future,” says Ms Arapere.

Community

The Panel was continually amazed by the stories shared with them by mana whenua and other communities they met with during the course of the review.

“Not only was the information instructive, but the selfless actions of individuals, whānau, and whole communities during and after the flood impressed us in ways that cannot be expressed and will stay with us.

“There was a range of perspectives on the extent to which and how HBRC works with communities in relation to flood management, planning and recovery. One persistent theme was the lack of meaningful engagement and that local knowledge and perspectives were not seen by HBRC as being useful.

“The panel considers that as HBRC leads the region’s response to Cyclone Gabrielle and makes it more resilient to future floods it needs to augment its toolbox, making more and better use of the networks and knowledge that exist within communities.

“It is essential that HBRC treats the region’s communities as project partners, rather than consulting and seeking feedback once much of the scoping and critical thinking has already occurred.

“Community and stakeholder participation is fundamental to managing flood risk, as is recognising that flood risks will affect many people and can include transferring risk from one community to another.

“The community is mobilised, organised and motivated to progress improvements in flood risk management infrastructure and processes. HBRC and the community should make the most of this, learning the lessons from the event to progress and implement effective new and improved flood risk management solutions for the many areas in the region that will forever be subject to flood risk,” says the panel.

HBRC Resourcing and funding

The resourcing and funding of day-to-day river and flood management activities is considered to be inadequate in many areas, and was exacerbated during the cyclone, the panel says.

“From a regional perspective, the cost of rebuilding and improving flood management infrastructure is likely to be unaffordable so central government assistance will be needed.

“This is especially so given the need to re-imagine legacy systems so they are fit for purpose, and reflect the evolving best practice of making room for the river.

“The current model where most of the funding is derived from targeted local rates will not be sufficient to fund long-term solutions.

“This is a significant issue for smaller rural communities, and especially Māori communities where the value of land that has been marginalised over decades is considered insufficient to cover the cost of its protection.

“The need for central government funding along with a greater regional contribution is likely to be needed to achieve an affordable and equitable funding regime.”

In conclusion, the panel acknowledges the deep hurt, loss and anger existing in communities as result of the cyclone.

“The lessons learned from this independent review and what comes next are of the utmost importance,” the panel says.

NOTE:

About the Hawke’s Bay Independent Flood Review

The Independent Flood Review was instigated by Hawke’s Bay Regional Council in the wake of Cyclone Gabrielle and the flooding that significantly impacted the region. The Review is independent of the Council and covers all of Hawke’s Bay from Wairoa to Pōrangahau.

The purpose of the Review was to seek to understand the circumstances and contributing factors that led to the flooding. This includes looking at flood management schemes and programmes and how each performed, the decisions made by the Council during the cyclone, and whether these remain viable.

The Review did not look at district or city council roles/responsibilities during the cyclone, the local civil defence emergency management response, or the recovery phase of the flood event.

A panel of three independent reviewers is conducting the Review, with experience in resource management, engineering and the law, as well as experience in these types of reviews.

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