The Auckland region has a high exposure to coastal hazards including coastal instability and erosion. These hazards can present a safety risk, adversely affect property and infrastructure, and damage or destroy cultural and environmental sites. A programme of research has been undertaken to identify, at a regional level, the Area Susceptible to Coastal Instability and/or Erosion (ASCIE). ASCIE is the area landward of the current coastline that is at risk because of coastal erosion or instability caused by coastal erosion. The study forecasts the areas of Auckland’s coastline that could be affected by coastal erosion and instability under a range of climate change (sea-level rise) scenarios and timeframes.

This data is mapped at a 0.5 km to 5.0 km scale and is not intended for site-specific use other than to determine whether more detailed study is warranted. Due to the large scale of the assessment (i.e., 0.5-5 km resolution) errors are inherently introduced due to the variance within a coastal cell. To identify areas that could potentially be susceptible to coastal instability and/or erosion typical upper bound values have been adopted for each coastal cell. This means that in some areas the ASCIE may be overpredicted (i.e., shown further landward). However, this also means that in ASCIE may be underpredicted in areas where values are larger than the typical upper bound value (i.e., the largest or maximum values). Therefore, this assessment is

recommended to be used as a preliminary tool. The regional-scale ASCIE can be refined by undertaking an assessment on a more detailed scale.

https://www.knowledgeauckland.org.nz/publications/predicting-auckland-s-exposure-to-coastal-instability-and-erosion/

The regional-scale assessment of ASCIE is based on available data and tools and understanding of

coastal processes. Uncertainty may be introduced to the assessment by:

• an incomplete understanding of the parameters influencing the areas susceptible to coastal instability and/or erosion

• an imprecise description of the natural processes affecting, and the subsequent quantification of each individual parameter

• errors introduced in the collection and processing of data

• scale of assessment and variance in the processes occurring within individual coastal cells

• other hazards such as land based geotechnical instability, or planning and landscape impacts etc. that are not accounted for within the ASCIE

• adopted methodologies

Lineage:

The methodology used to identify these areas is presented in Auckland Council Technical Report RT2020/021 “Regional Assessment of Areas Susceptible to Coastal Erosion and Instability” available on the Knowledge Auckland website.

Creation Date:

31/05/2021