Auckland’s exposure to sea level rise: part 1 – regional inventory

Author:
Nancy E Golubiewski , Kyle Balderston, Chad Hu, Jamie Boyle
Source:
Auckland Council Research and Evaluation Unit (RIMU) and Chief Sustainability Office
Publication date:
2019

Executive summary

The regional sea level rise inventory assesses Auckland’s potential exposure to sea level rise and coastal inundation. To do so, it uses both land elevation bands as a proxy for a series of sea level rise (SLR) scenarios and coastal inundation models to consider extreme storm events under present and future regimes. The two approaches permit a simultaneous consideration of changing coastlines as a result of sea-level rise (an altered environment) and extreme events.

Presented as a data compendium, this report catalogues the spatial intersection of various entities of interest with the elevation band/sea level rise and coastal inundation models; exposure is simply defined as two-dimensional co-location. This information can be used to inform and guide work programmes and research projects that seek to address and understand more about the implications, vulnerabilities and total risk that arise from this current and ongoing component of climate change.

Key findings from the data summaries that follow include:

  • Approximately 1.5%-4.5% of Auckland’s land area sits in low-lying coastal areas that could be exposed to SLR ranging from 0.25m to 3m.
  • Over the last decade population grew faster in the areas exposed to sea level rise than in the region overall; approximately three per cent of Auckland’s population is estimated to be in low-lying areas affected by the SLR and coastal inundation scenarios used in this report.
  • Mangroves are the most exposed ecosystem type in terms of both area and proportion. Substantial proportions of coastal ecosystems are increasingly affected with projected sea level rises through the 21st Some indigenous coastal and scrub forests are somewhat exposed to SLR and inundation, whereas other indigenous scrub (such as kanuka and manuka) and tall forests (such as kauri and tawa) are mostly located inland and are therefore less affected by sea level rise and coastal inundation.
  • In addition to the coastal ecosystems that would be exposed, the land cover category with the largest area potentially exposed to SLR is high-producing grassland. Likewise, the land use most exposed in terms of area is rural industry.
  • Prime soils are the most exposed Land Use capability class across all sea level rise scenarios, and elite/prime soils are disproportionately exposed.
  • The exposure of buildings to SLR and coastal inundation is different between the urban and rural parts of the region. Higher numbers and proportions of buildings could be exposed in rural areas than in the urban core and periphery through 1m of SLR. However, under larger SLR scenarios and coastal inundation combined with SLR, the number of buildings exposed is greater in the urban core and periphery than in outlying rural areas.

In contrast to the gradually changing coastline that will result from sea level rise, coastal inundation occurs as an acute event. Thus, the nature of a storm event is distinct from ongoing sea level rise. In addition, the definition of the same magnitude storm event will have decreased (becoming more common) by the end of the century when 1m SLR is projected to occur. With this in mind, the areas exposed to coastal inundation under both current and sea level rise conditions are similar to those of 1m and greater sea level rise scenarios. That is, inundation impacts will affect larger areas sooner than sea level rise alone.

Auckland Council technical report TR2019/017

Climate Change Risk Assessment CCRA 2019 series

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Climate Change Risk Assessment 2019

As communities across the world set out to plan for climate change mitigation and adaptation, they first seek to understand how climate change will affect their city, region, or country.

The Climate Change Risk Assessment (CCRA) has been produced by Auckland Council’s Research and Evaluation Unit (RIMU) in support of the Auckland Climate Action Plan (ACAP) at the request of the Chief Sustainability Office. Its aim is to provide information about the risk and vulnerabilities the Auckland region may face under a changing climate regime, which is already underway. In 2018, national climate change projections were scaled-down to produce a more specific picture of their likely effects within the Auckland region. Based on this, CCRA adopted the Intergovernmental Panel on Climate Change’s (IPCC) representative concentration pathway (RCP) 8.5 (“business as usual”) scenario as its guiding projection, given the lack of evidence of any meaningful and sustained decreases in emissions that would shift to other projection pathways.

The eight reports in the CCRA consider various components of key risks – that is, hazard, exposure, and vulnerability – across sectors and systems of interest: people (heat vulnerability, climate change and air quality), society (social vulnerability and flooding), and natural environment (terrestrial and marine ecosystems), as well sea level rise at regional and local scales. A summary report has also been produced.

Titles in the Climate Change Risk Assessment (CCRA) series:

An assessment of vulnerability to climate change in Auckland. Fernandez, M. A. and N. E. Golubiewski

Development of the Auckland Heat Vulnerability Index Joynt, J. L. R. and N. E. Golubiewski

Air quality and societal impacts from predicted climate change in Auckland Talbot, N.

Climate change risk assessment for terrestrial species and ecosystems in the Auckland region. Bishop, C. D. and T. J. Landers 

Climate change risk assessment for Auckland’s marine and freshwater ecosystems. Foley, M. M. and M. Carbines

Flooding risk in a changing climate. Golubiewski, N. E., J. L. R. Joynt and K. Balderston

Auckland’s exposure to sea level rise: part 1 – regional inventory. Golubiewski, N. E., K. Balderston, C. Hu and J. Boyle

Auckland’s exposure to sea level rise: part 2 – local inventory (forthcoming). Boyle, J., N. E. Golubiewski, K. Balderston and C. Hu

Summary: Climate change risks in Auckland. Auckland Council. Prepared by Arup for Auckland Council 

Last updated: 2019-03-20

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