Looking ahead: Flood forecasting for Greater Wellington Regional Council

Looking ahead: Flood forecasting for Greater Wellington Regional Council

Flood Early Warning Systems (EWS) can save many lives and reduce flood loss and impact by allowing emergency responders and the public time to act. Science and technology advancements have rapidly improved data observation, modelling and flood forecasts for disaster risk reduction (DRR). Flooding is considered one of New Zealand's biggest natural hazards, costing around $17 million a year in insurance payments and $15 million in emergency management expenditure between 1968 and 2017.

In Wellington, New Zealand, work is currently under way to establish a forecasting and early warning system for Greater Wellington Regional Council (GWRC) in partnership with the Wellington Region Emergency Management Office (WREMO). With the support of UK-based RAB Consultants, Tonkin + Taylor (T+T) is reviewing current flood response procedures for the Wellington region, researching new flood forecasting capabilities, and providing recommendations for community engagement. With the climate constantly evolving and changing, a circular approach is crucial to allow for ongoing feedback and revisions. This allows for procedures to be upgraded, ensuring the safety of lives and livelihoods. 

T+T flood risk and emergency management specialist Alex Cartwright, GWRC Senior Engineer – Flood Protection Hamish Smith and RAB Consultants Director of Resilience Bryan Nelson worked extensively on the project. We asked them to share their insights with us on the importance of flood forecasting, early warning, and how we as individuals and organisations can get ready to respond to and recover from flood events.

What are flood procedures? How do they work?

Alex: Flood procedures capture key actions to reduce risk before, during and after flood events. All organisations have procedures of one form or another (think of the fire evacuation plan), they are the document that supports incident staff in their roles and responsibilities. Flood procedures vary depending on the type of flood event, the catchment, and responsibilities of each agency. In a New Zealand context, for river flooding, regional councils, unitary authorities, other authorities and relevant organisations (e.g. energy companies) maintain flood procedures (or manuals) that capture their key actions to reduce risk during flood events.

Procedures are vital to ensuring that responders are all working to the same process, helping rather than hindering the situation. Procedures need to be relevant, and written in a format that can be easily understood when people are working under the stress and anxiety of responding to a flood. This often means procedures are broken down into in-depth processes, along with clear summary diagrams, flowcharts and checklists that can be used during an event.

By having differing steps dependent on the size of an event, procedures can scale with the needs of a given event. Actions and decision points within procedures are tied back to trigger levels wherever possible. Forecasting and EWSs help understand the likelihood of reaching trigger levels, informing the response. The saying is that, “Flood response starts in the dry, as do procedures, helping document processes and actions that can be taken”.

What are the differences in response between a small-scale and large-scale flood?

Alex: The biggest difference is the amount of resource required. Most events start small, with some growing large. The number of people and other resources required increases exponentially with the scale of a flood event. This is one of the biggest challenges in managing a flood incident. Larger flood events have increased impacts, generally resulting in more impacted people, more potential damage, and longer-lasting impacts. While minor events may pass in a few days, major events can result in recovery efforts that last months and years. Larger scale floods are also likely to attract more attention from media and politicians.

Tell us about the value of working with an international consultant like RAB? What’s it been like working on a project from different sides of the world?

Hamish: It was the strengths and value of the international team that lead us to select T+T/RAB during the competitive bid process. The project team were able to take learnings from the UK flood risk scene, which has been under a lot of scrutiny over the last couple of decades, and put a New Zealand flavour on the project.

Through the project, where we identified roles that would benefit from formal training, such as our senior managers, the team were able to develop new supporting material very quickly.

It’s also worth saying that this project was forged in the fires of the global pandemic. We kicked off in January 2020 - what now seems a very different time. The international team adapted material to work online very quickly, and this also allowed staff in the UK to participate more easily. As a result, our Flood Response team have advanced our online ways of working which makes us more resilient – although we also need to practice for when technology does go down.

Bryan: I have 30 years’ experience in flood resilience in the UK working with both private and public sector clients. Life in NZ is very similar to the UK, but the approach to flood resilience is a few years behind. Therefore, for me, it’s been great to have had the opportunity to influence my experience in putting GWRC in a better place to prepare and respond to floods. The biggest challenge has been the time zones with many early morning and late evening calls. Working with T+T made this easy - their inclusive approach and joint communication throughout the project meant we were always aware of progress and developments.

What are the benefits of globally connecting organisations to tackle resilience and flood risk?

Bryan: I’m a strong believer in collaborative working, it’s the key to maximising expertise and experience. But teaming up with the right partner for the right project is the challenge. The similarities and connections between the UK and NZ, along with shared values across the T+T/RAB team provided the perfect mix of proximity and expertise in NZ along with knowledge and experience from the UK. In this project, GWRC were extremely receptive to new ideas and ways of working which has put the organisation at the forefront of preparedness with procedures in place and duty officers engaged, trained and exercised.

Alex: RAB Consultants are industry leaders in flood forecasting and emergency management. They bring challenge of thought and differing approaches that have as yet not been undertaken in New Zealand. Being able to connect the breadth and depth of skills and experience both in New Zealand and Internationally is vital to delivering better outcomes for our clients and communities. These types of projects require a collaborative approach, and that is the way that we work, partnering across RAB, T+T and GWRC to deliver collaborative outcomes. The connections are made even easier given that I previously worked with RAB when based in the UK.

What are the benefits that an early warning system will provide to the Greater Wellington’s communities?

Alex: Similar to how we benefit from daily weather forecasts, flood forecasting models give more in depth analysis of what projected rainfall could lead to within our river systems. This provides understanding of flood risk, to varying levels of confidence. Time to prepare is very valuable in any emergency response, as it allows proactive steps to be taken to reduce risk and put information in the hands of those that need it. Even in rapid response catchments, where warning times are less than 4hrs, lots can be achieved with the right planning.

What did the flood forecasting/flood warning development phase require?

Hamish: GWRC and the team from T+T/RAB conducted an international market sounding and assessment of options and approaches for flood forecast platforms and models. We wanted to see what was being done in New Zealand and internationally, as this space is rapidly evolving.

This phase involved identifying a modelling methodology and requirements to provide a forecast-led warning service. We then established a pre-emptive flood warning system for each catchment managed by GWRC where people and property would be at risk. These needed to allow for useable degrees of confidence and enough lead time for proactive response actions to take place. Finally, we developed a prioritised programme for flood forecasting system implementation across the region, that would provide the capability to meet these objectives. 

Why does a flood forecasting system need updating? What do you see in the future for this system?

Alex: Flood forecasting systems need to be reviewed and updated as we increase our understanding of changes in the environment, such as the impacts of climate change. They also need to be updated to reflect the communities’ needs as we change how we interact with the environment (e.g. where we live, work and play). This means considering the underlying information that goes into flood forecasting models (river flows, environmental conditions etc) along with trigger levels and warnings that are provided.

As our communities become more aware of flood risk, information can be further refined, and hopefully we will see increased open access to flood forecasting and warning information across New Zealand as other countries have developed. Being able to see an interactive map of New Zealand’s rivers with active flood warnings shouldn’t be a too distant future dream.

What can people in the community do to get involved with this initiative?

Alex: Firstly, communities should look to understand their own flood risk where they live, work and play. Understanding your flood risk is the first step, then it’s looking at how to best prepare for flood risk and making a plan - just like we do for earthquakes.

Hamish: There is always something the community can do to better these projects. We’ll continue updating you on how we’re progressing, but also feel free to ask us how we’re getting on in a few months. Please do reach out to share your knowledge with us about the impact of flooding in your area. We're always keen to learn from others.

More info can be found on the official WREMO website or GetReady.govt.nz.