Skip to content

Response: Managed retreat from coasts and rivers

Home > Climate wiki > Response > Managed or chaotic retreat

Managed retreat from coasts and rivers

Summary

  • Managed retreat is the deliberate and coordinated decision to move structures and communities away from the increasing risks posed by rising sea levels and floods. The Government’s national adaptation plan (August 2022) outlines processes to enable managed retreat.
  • Managed retreat is outlined in Chapter 5 of the Government’s national adaptation plan (2022). It supports working with nature to build resilience’, by ‘Restoring and protecting indigenous ecosystems, identifying sites that need buffers against climate risks and supporting communities in understanding nature-based solutions as a choice for adaptation.’ This means restoring critical natural infrastructure such as healthy coastal dunes, braidplains and wetlands. This highly effective adaptation strategy can reduce flood and sea level rise impacts while also helping to mitigate climate change by sequestering carbon in soils and blue carbon, and improving biodiversity and mahinga kai, and thus, economic and social resiliency.
  • Chaotic retreat is uncontrolled, forced as a result of flooding, erosion, large-scale damage, and sometimes deaths and injury. It is commonly accompanied by Government and councils being blamed for failing to construct adequate defenses and/or for allowing buildings to be constructed in areas known to be hazardous.
  • Who pays? A portion of our rates and taxes pays to protect property and infrastructure (drains, levees, seawalls etc.) against river and ocean hazards (erosion and flood). However, these were constructed to defend against a climate that no longer exists. Councils and homeowners can insure property but costs are increasing. As climate change intensifies, some infrastructure and private property will be denied insurance.

“Even after adjusting for inflation, we can see that the cost of these floods and large events over the last 10 years is the equivalent to the previous 45​ years.”Blair Turnbull, CEO, Tower Insurance (Stuff)

  • Many Kiwis already live in high-risk areas, some of which may cost more to protect than their market value. In 2019, NIWA assessed Canterbury’s current flood risk to be $40 billion (based on 2016 values). As for sea levels “...72,000 New Zealanders [are] currently exposed to present-day extreme coastal flooding, along with about 50,000 buildings worth $12.5 billion.”
  • Choices: managed retreat from high-risk coastal areas and flood plains (controlled, safer, more cost-effective), or wait until disaster strikes before being forced to retreat (chaotic, dangerous, potentially deadly, and costly). Both options are costly. Who pays?
  • ‘Community engagement on climate change adaptation’ found that process of engaging with communities at risk to help make the best, albeit unpalatable choices are hindered by a lack of resources, vague policies, and ill-defined laws that pit developers against councils faced with potential liability for declining development and future liability from affected owners, for permitting it.

Home > Climate wiki > Response > Managed or chaotic retreat

Summary

  • Managed retreat is the deliberate and coordinated decision to move structures and communities away from the increasing risks posed by rising sea levels and floods. The Government’s national adaptation plan (August 2022) outlines processes to enable managed retreat.
  • Managed retreat is outlined in Chapter 5 of the Government’s national adaptation plan (2022). It supports working with nature to build resilience’, by ‘Restoring and protecting indigenous ecosystems, identifying sites that need buffers against climate risks and supporting communities in understanding nature-based solutions as a choice for adaptation.’ This means restoring critical natural infrastructure such as healthy coastal dunes, braidplains and wetlands. This highly effective adaptation strategy can reduce flood and sea level rise impacts while also helping to mitigate climate change by sequestering carbon in soils and blue carbon, and improving biodiversity and mahinga kai, and thus, economic and social resiliency.
  • Chaotic retreat is uncontrolled, forced as a result of flooding, erosion, large-scale damage, and sometimes deaths and injury. It is commonly accompanied by Government and councils being blamed for failing to construct adequate defenses and/or for allowing buildings to be constructed in areas known to be hazardous.
  • Who pays? A portion of our rates and taxes pays to protect property and infrastructure (drains, levees, seawalls etc.) against river and ocean hazards (erosion and flood). However, these were constructed to defend against a climate that no longer exists. Councils and homeowners can insure property but costs are increasing. As climate change intensifies, some infrastructure and private property will be denied insurance.

“Even after adjusting for inflation, we can see that the cost of these floods and large events over the last 10 years is the equivalent to the previous 45​ years.”Blair Turnbull, CEO, Tower Insurance (Stuff)

  • Many Kiwis already live in high-risk areas, some of which may cost more to protect than their market value. In 2019, NIWA assessed Canterbury’s current flood risk to be $40 billion (based on 2016 values). As for sea levels “...72,000 New Zealanders [are] currently exposed to present-day extreme coastal flooding, along with about 50,000 buildings worth $12.5 billion.”
  • Choices: managed retreat from high-risk coastal areas and flood plains (controlled, safer, more cost-effective), or wait until disaster strikes before being forced to retreat (chaotic, dangerous, potentially deadly, and costly). Both options are costly. Who pays?
  • The Local Government New Zealand report ‘Community engagement on climate change adaptation’ found that process of engaging with communities at risk to help make the best, albeit unpalatable choices are hindered by a lack of resources, vague policies, and ill-defined laws that pit developers against councils faced with potential liability for declining development and future liability from affected owners, for permitting it.

What do we choose to save and what do we chose to sacrifice?

Lessons from the recent past

One of the world’s most exensive natural disasters was the 2010-2011 Canterbury earthquake sequence. Of the many things learned during and following the disaster, three takeaway messages directly relevant to our response to the climate crisis stood out.

1. Forewarned

The potential for major earthquakes and liquefaction in the region was publicly documented geological science, with warnings embedded in local council reports. Yet few people knew of or believed the risks existed because scientific knowledge is often not communicated well, can be disputed by vested interests such as property developers, or clouded by history underpinned by engineering hubris: the flawed assumptions that Christchurch had been there for over 150 years and its building codes were designed to withstand predicted loads of a 500-year seismic event.

The first quake of 7.1 magnitude struck September 2010. It caused cosmetic and structural damage to multiple buildings and created an impressive 29.5Km long ground rupture. Although two people died, the general feeling was that due  to stringent building codes, we had weathered a once-in-a-lifetime very large magnitude event.

2. Displacement

The 6.1 magnitude quake that followed in February 2011 killed 183 people. Buildings were hit with ground motions that “considerably exceeded even 2500-year design motions.” Entire suburbs were lost and land irreparably damaged. It was traumatic—socially, economically, psychologically, spiritually, physically. For many, the quakes felt like a betrayal of the home where they had lived in and loved, and so they left with no intention of every returning.

Yet many didn’t want to leave. When forced to evacuate because their homes were unlivable or critical infrastructure had been destroyed, they wanted to rebuild, preferably in the same location.

This is not unique to Canterbury. It’s a global phenomenon. Here in Aotearo, regardless of whether people identified as Māori, Pākehā, Pacifica or Asian, the reasons for this desire to rebuild can best be described as tūrangawaewae—a sense of place, of familiarity, of whakapapa, whānui and community.

The initial trauma was compounded when the Government declared that some places—the Red Zones—were so damaged that inhabitants could never return. The people and communities that once lived here became refugees or were internally displaced. Those that evacuated to surrounding areas placed enormous pressure on their host communities that were themselves struggling with their own temporary damages and losses. The impact on small host communities hit by a deluge of unprepared and largely unprovisioned evacuees has never fully been recognised nor considered in terms of future disasters.

3. No end in sight

When a fire or hurricane strikes, people experience an immediate trauma, sometimes followed by post-traumatic shock. They may choose to leave or rebuild.

But the earthquakes were not a single vent. Aftershocks kept coming, and no one could say when they would end. Or even if they would end. Decisions to rebuild were delayed or abandoned. Trauma was compounded. Four years later many people were stilling battling for insurance, still living in temporary accommodation. Others had settled into new homes, many to the north of the city and towns like Kaikōura. And then the 7.8 magnitude Kaikōura earthquake stuck. It seemed unfair, inconceivable. But this was the reality. The science was and still is clear: another major earthquake could hit anytime.

Applying lessons to the future

The power of tūrangawaewae, our sense of place, is once again under threat. This time from climate change. The evidence is  uncompromising. We have been forewarned. Displacement is inevitable, and there is no end in sight as the climate will continue to change for generations to come. Both the science and events already unfolding make that clear.

Sea levels are rising and the pace is accelerating. Because warming will continue, storms will be more powerful and floods will become more frequent and stronger. Infrastructure built from rates and taxes collected over generations is being eaten by waves, drowned by rivers reclaiming their stolen braidplains, or overwhelmed by so much rainwater that they simply cannot drain it an ocean too high or a river too swollen. Ultimately, many places will become uninhabitable because the cost of defending them is beyond our financial capability, even though it’s technologically feasible. (The Dutch have been doing this for centuries, so they’ve had the time and money to prepare).

Displacement is inevitable. And there is no end in sight as the climate will continue to change and sea levels will continue to climb for generations. That’s what the science tells us. And that’s the reality already unfolding.

Past emissions have already changed our climate and will continue to do so in years to come. How much more change and how fast change will happen depend on every country’s contribution to reduce global emissions.” Vicky Robertson, Secretary for the Environment, National Adaptation Plan 2022

 Options:

1. How do we choose to retreat from hazard zones?

(a) Managed (proactive): Consult with communities and undertake risk analyses based on current knowledge. Examples how to do this are included in: ‘Using current legislative settings for managing the transition to a dynamic adaptive planning regime in New Zealand‘ (National Science Challenge) and ‘Community engagement on climate change adaptation: case studies‘ (Local Government NZ). Using an adaptive management approach, choose to defend what we can afford to based on a cost-benefit analysis now and in the next few decades, and retreat from what we can’t. Agree on staged retreats triggered by certain events rather than time scales, as this will allow for new science, information, and observed events such as the sudden collapse of ice sheets raising sea levels faster than currently forecast, or change in ocean currents driving more powerful storms. Decline consents to construct non-portable structures in at risk locations.

Rebuild critical natural infrastructure during the retreat, as this will act as a buffer against rising sea levels and floods, buying more time to migrate infrastructure and building in safer locations.

(b) Chaotic (reactive): ignore the problem and let the ocean, rivers, and storms force retreats on an ad hoc basis.

2. Who pays? (see the NZ Deep South Research report)

(a) Managed: consult with communities to agree how costs will be shared equitably. A controlled retreat is far less costly, as decisions can be made early to retire and dismantle at-risk aging infrastructure and rebuild it in less vulnerable locations. Council/government purchase of at-risk land assisted migration using lessons learned from the Christchurch earthquakes. Money should not be wasted on new developments in risky areas.

(b) Chaotic: pay following each event. The cost will include lives lost due to loss of critical built infrastructure, the economic and social cost of caring for internally displaced people, lost productivity, and the concurrent impacts on host communities that may be simultaneously grappling with some lost services and critical infrastructure. As rising sea levels and storms/floods will be ongoing, this approach ultimately risks economic and social collapse as costs across all sectors become unsustainable as climate change escalates.

A special issue on Managed Retreat in the journal Science Out of Harm’s Way‘ is freely available online as this is a global problem, and research and lessons learned elsewhere are applicable here. Other key references are listed below.

 

Environment Canterbury manages 59 river and drainage rating districts (i.e. areas where ratepayers contribute to the cost of flood protection). This map shows each rating district around rivers. Areas outside these zones are not protected from floods.

Under the Canterbury Water Management Strategy, the catchment of each waterway—their wetlands, groundwater, springs, lakes and rivers that flow down to estuaries—is considered together. Managing catchments in this integrated way means problems can be considered based on each catchment’s unique attributes. These maps will help you identify which catchment zone you are in. Note that while there is overlap, these zone are not the same as river-ratings districts.

More information