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Coastal cities: What's in store?

A Rising Tide - The future for our coastal cities LG May 2016 Featured Image

Plans for New Zealand’s coastal cities must take into account ways to accommodate higher sea levels. By Liam Foster from Opus International Consultants.

Rising seas will be one of the greatest challenges that our communities, and in particular our coastal cities, face. Only a proactive and unified approach will give us the chance to enable coastal cities to continue to thrive and minimise the mass disruption that will likely occur. Such action must be taken now and this will require a strategic vision across all levels – from individuals through to central government.

The development of cities within coastal environments has largely mirrored the development of cities across the world. The key focus for encouraging settlement was to control water through the urban environment, resulting in changes to the natural hydrological cycle. This effectively encouraged systems to remove stormwater from urban areas as fast as possible, through the provision of gravity or pumped systems.

Liam Foster is stormwater and flood risk management national lead at Opus International Consultants.
Liam Foster is stormwater and flood risk management national lead at Opus International Consultants.

The performance of these systems can be adversely affected by sea level rise. Several communities around New Zealand, along with many others across the world, are sited below current mean high spring water levels posing huge challenges in how to manage rainfall within their catchments. The problem will be further compounded by rising sea levels, and more frequent and intense rainfall events.

Pumping is therefore required to maintain the levels of service as gravity systems are unable to serve these urbanised areas. The current management approach in these areas is such that every drop of water that falls must be pumped out. Communities and cities in these low-lying areas rely upon these forced drainage systems to keep them dry.

This approach is both resource-intensive and vulnerable to more intense storms, as design guidance for stormwater management in these areas often focuses on more frequent events. The investment required to achieve better levels of protection against more extreme events is often hard to justify.

The responses to a series of catastrophic events around the world – such as Hurricane Sandy in New York, Hurricane Katrina in New Orleans or the Copenhagen Cloudburst of 2011 – show that an alternative and coordinated approach can deliver sustainable coastal communities. These are not purely focused on delivering the status quo but look to create additional benefit for multiple outcomes.

At their core, all these responses require effective planning to focus on the long term – rather than across short political timelines. They incorporate the concepts of scenario planning and widespread cross-community engagement to deliver a proactive approach to managing a changing climate and rising seas.

New Zealand must urgently change the way it plans, builds, designs and responds to at-risk communities and this requires greater levels of coordination and improved communication between stakeholders, as well as some very creative thinking to deliver financially sustainable urban drainage solutions.

If these issues are ignored the likely consequences are serious. They could include hazardous fast-flowing floods, potential loss of human life, residents displaced from homes, enduring psychological damage, loss of critical coastal habitats, abandonment of cities, billions of dollars in damage and local/regional economic collapse.

Alternatively, we can seek to deliver more resilient communities that live with water and can derive integrated multifunctional and economically-advantageous solutions.

Taking a long-term view of the future of our cities across New Zealand, we should look to adapt our thinking and approaches to help alleviate the likely consequences of sea-level rise and future stormwater issues. Such issues may include:

  • The extent, depth and frequency of flooding will increase.
  • Continuing intensification of coastal cities putting further pressure on already-strained urban drainage systems.
  • Other factors such as land subsidence in low-lying areas may exacerbate the flood risk profile.
  • Costs of damages are likely to be substantial.

Central government leadership is required to identify that New Zealand should plan for the long term. Following the advice of a 2015 Parliamentary Commissioner for the Environment report, Preparing New Zealand for rising seas, all future city plans must take into account ways to accommodate higher sea levels.

Communities must take the opportunity to decide amongst themselves their appetite to adapt to the future risks. Options may include retreating from areas of risk or continuing to defend. They must also look at understanding how they can best work with stormwater rather than remove it as quickly as possible.

The financial, social and environmental benefits of proactively delivering climate change adaptation far outweigh the potential costs associated with future damaging events.

Communities around coastal New Zealand need to learn the lessons from other geographies quickly to avoid having to repeat the recovery process and needing to derive our own approaches to significant natural hazard events.

We have the opportunity now to choose our overall management strategy for delivering resilient stormwater futures. New approaches can bring multiple beneficial outcomes through the delivery of integrated blue/green and hard stormwater management systems.

A philosophical change in our psyche to learn to live with water and view it as a valuable resource or commodity rather than a nuisance is key to our ability to deliver sustainable and successful coastal cities long into the uncertain future.

See Liam Foster’s full presentation to the Water New Zealand Stormwater Conference here.

Liam Foster_Opus_Stormwater Conference_Abstract

  • Liam Foster is stormwater and flood risk management national lead at Opus International Consultants. 

Stormwater Conference 2016

Liam Foster will be talking about the future of New Zealand’s coastal cities at Water New Zealand’s Stormwater Conference 2016 in Nelson, May 18 to 20. He is stormwater and flood risk management national lead at Opus International Consultants

The conference focuses on resilient stormwater systems in recognition of recent significant damaging rainfall events across the country and the effect this has had on infrastructure and communities.

Water New Zealand Stormwater Conference committee chair John Palmer says the stormwater industry has an important role to play in ensuring that our stormwater infrastructure has resilience built into it and at the same time delivers on the many opportunities that it presents.

“Building resilience into the stormwater infrastructure requires an integrated and collaborative approach,” he says. “There are many fine examples of work being done across the country that need to be shared, acknowledged and celebrated.”

More information at: 

This article was first published in the May 2016 issue of NZ Local Government Magazine.

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