Wet and forget: why this attitude to flooding needs to change

Water New Zealand Stormwater Group chair, Peter Christensen says our boom and bust cycle of quick fixes needs change.

The summer events have caught the attention of the nation in a way that other flood events have not. Yet since floods are Aotearoa New Zealand’s most frequent natural disaster we only need to scan through past news media to see that flooding is a common headline.

Calls to ‘fix flooding’ overlook the nature of natural hazards. They can’t be neatly solved and forgotten: there will always be a bigger event or one that falls outside of design parameters and we need to move away from the mentality that nature can be squashed into a box and contained. Climate change impacts are already making these scenarios more frequent and severe, and without a new way of thinking we will continue to see lives lost and buildings flooded.

Flood and forget

The current model for addressing urban stormwater flooding is often driven by a big flood. This kicks off a cycle where attention is focused on the areas that flooded, reactive work commences, there is a dryer period where attention drops off, and then further flooding restarts the cycle again.

Currently, less than 15% of the national Three Waters budget is spent on stormwater. While infrastructure is only a part of the solution, this small sum is indicative of the attention paid to stormwater. Unfortunately, investment in flood management is easily pushed aside as the most recent flood recedes in people’s memories.

Worse still, the current event-based funding model works for communities with a strong political voice and widespread immediate issues, but doesn’t work for areas of socio-economic deprivation (which often overlap with vulnerability to flooding, but have a weaker voice); for isolated pockets of flooding; or where there is flood risk that has not yet been realised. This model also struggles to strategically address the predicted long-term impacts of climate change and other areas where long-term planning is required.

The rainfall Auckland experienced this summer is beyond what can be economically managed with traditional infrastructure. Stormwater systems are not and cannot be designed to cope with that much runoff, and it is not realistic to invest in unaffordable infrastructure for such infrequent events. However, there is still much that can be done to reduce the damage caused by flooding.

Beyond the quick fix

So, what’s the alternative to the boom and bust cycle of post-flood quick ‘fixes’ followed by forgetfulness? This question is not new, and the Auditor General’s report on stormwater[1] in 2018 effectively addressed the same question. To enable real improvements to occur a hierarchy of measures is needed, starting with ‘avoid’ and ending (if we have to!) with hard infrastructure like pipes as illustrated in Figure 1.

Figure 1: Flood management hierarchy (Based on Clare Feeney, Environmental Communications Ltd)

Quick fixes often start at the bottom of the pyramid (‘pipe’ and ‘delay’) and seldom reach the upper levels of ‘reduce’ and ‘avoid’. However, that is where real change and investment are required, and the rest of this article focuses on improvements we need to make in those spaces.

A national level of service

New Zealand lacks a national level of service for flooding, so standards vary widely throughout the country. Without a national standard incorporating climate change and uncertainty, it is difficult to establish the secure and reliable funding required to drive a strategic approach. Instead, we often follow a largely reactive, inequitable and inefficient approach. As an industry, we need to push for the development of national levels of service for flooding and incorporate this into our investment planning.

A national level of service for flooding will help inform new greenfield development and intensification, but what about communities already subject to inundation? Having a national level of service will shine a spotlight on places that don’t meet the standard and inform prioritisation of the most at-risk areas for improvement. With no national minimum levels of service and with our currently haphazard accountability for managing flood risk, problems can be hidden and overlooked for decades between events.

A national level of service also needs to make it crystal clear who has accountability for flood-related outcomes. At present accountability for flooding is often split across agencies or departments within agencies. As flood management systems are used relatively infrequently, it can be all too easy for everyone to think it is someone else’s job and for no one to realise that the ball has been dropped. The impacts of this become apparent during a flood, but by then it is too late.

Communicating flood risk

The first three recommendations of the Auditor General’s 2018 Stormwater Report hinge on having clear levels of service and making sure that people understand their flood risk. The report recommendations are still relevant, stating that councils need to:

  1. understand the current and likely future flood risks in their district or city sufficiently to take a proactive approach to reduce the risk and effects of flooding;
  2. provide elected members with the necessary information and options, including about local flood risks and their stormwater systems, to make well-informed and deliberate decisions about investment in their stormwater systems;
  3. improve the information they make available to their communities so that people can understand:
    • the potential risk of flooding;
    • what the council is doing to manage that risk, including how it is managing the stormwater system and at what cost; and
    • what the remaining risk is to the community;

Some councils are doing well in understanding where the flood risk is – Auckland has had flood-prone areas and overland flow paths mapped for over a decade – but many in the community still do not understand the risk they are living with. We need to learn how to communicate risk better. Do people understand that a ‘1 in 100-year flood event’ is really something with a 1% probability of occurring each year? And that if they live for 20 years in a house with a floor at the 1% flood level, then there is nearly a 20% probability of them experiencing a ‘100-year’ flood while they are there?

As experts in this field, we have to understand, help weigh up and communicate risk clearly so that households can make informed decisions about where they live or invest. As in Christchurch following flooding in 2014 and 2017, better explanations and demonstrations may also help the community to make the hard decision to relocate from the most affected properties.

Intelligent and equitable land use planning

Avoidance comes before minimisation and mitigation. Planning rules must be improved and rigidly enforced to prevent new investment in known floodplains and overland flow paths. While there are good examples around the country of planning for flood management, there is no national consistency. In addition, the resource consent process makes it possible for commissioners to ignore the advice of stormwater and planning experts. This is particularly problematic when it occurs during the District Plan process, as it can expose large areas to unnecessary risk for a long period of time.

There are equity issues too. As flood-prone land is often cheaper this can lead to the concentration of lower socio-economic communities in vulnerable areas. It is also inequitable if developers make their profit from poorly placed development but the risk and cost of disaster recovery are borne by homeowners and the wider community.

Good flood management also usually requires more land set aside for floodplains. This is expensive and so is often avoided as far as possible by developers. It is tempting to allow corners to be cut to follow the path of least resistance. After all, ‘It won’t flood there for 100 years, right?’ We need to stop allowing short-term thinking to influence decisions about communities that will be located in an area for decades, if not centuries.

Catchment-scale green infrastructure approach

Green infrastructure is important to build resiliency. However, while small-scale green infrastructure is vitally important to social well-being, improving water quality and restoring a more natural hydrological response in cities, it is not the ‘fix’ for flooding. We also need larger-scale green infrastructure like wetlands and basins as well as ‘making room for the river’ (or flood)’. Christchurch has invested in over 100 hectares of basins in the Upper Heathcote to significantly reduce flood risk along the river. This is the scale of investment that is needed to reduce flood risk in our cities.

Making room for flooding and learning to live with water means allowing the water space to move and pond, designing our cities around water (and other natural features) rather than trying to fight against it. There are good examples of this throughout the country. In Christchurch last year the council opted to cancel a project to build low stopbanks on staff advice that this would worsen existing flood issues and increase the residual risk.[2] In Auckland the daylighted Awataha Stream and Greenslade Reserve stormwater detention park held up well during the January floods, with much greater capacity than a traditional hard infrastructure network.[3]

There are strong links here with Te Mana o te Wai – thinking about water first and letting it have its own life. If we were to start our urban development by allowing space for water, including flooding, human health and well-being will follow. Correspondingly, if we try to squeeze water into the smallest pipe possible then human health and well-being will suffer.

Investing for resilient communities

A robust and effective flood management system is not cheap. It costs in terms of land set aside for wetlands, basins, overland flow paths and stream corridors. It costs to model and understand flooding for each location, and then to communicate this well. It costs in terms of building the necessary infrastructure to increase capacity and direct water away from vulnerable areas if possible.

While there is a high cost in configuring and reconfiguring our communities like this, there is a much higher cost to our communities – to people – when flooding inevitably occurs. Flexible and dynamic flood management, which integrates tools from planning (including retreat) to green infrastructure all the way down to pipes, pays off when flooding is avoided. As our climate keeps changing we are going to need to step up the investment in flood management to reduce the cost to our communities from flooding.

Changing our attitude toward flooding

The concepts described in this article are not new, and many in the stormwater profession have been advocating them for a long time. There are lots of silent success stories in our country (avoided flooding gets little media attention) and we need to be constantly telling the story of how harm can be reduced if we allow space for the flooding that will inevitably occur. We need to be advocates and storytellers not only at a local level but also at a national level helping to inform central government policy and planning.

Flooding can’t be ‘fixed’, but we can and must do a better job of reducing the risk and managing the effects. National standards, proactive risk-based investment, clear communication of risk, good planning and green infrastructure will all reduce the impacts of flooding. There are good examples of effective flood management in New Zealand, and we need to build on these. While floods will continue to be a part of our lives and we can’t pipe our way out of them, we can learn to live with them better so there will be less harm caused to our communities.

This article first appeared in the March/April 2023 edition of Water