Coastal developments at risk

Monitoring sites

Data is collected at all developed beaches on the Coromandel Peninsula, and along the developed shoreline of the Waikato and Waitomo Districts. This includes at least 26 settlements on the Coromandel Peninsula, as well as Port Waikato, Raglan, Marokopa, Awakino and Mokau.

Monitoring frequency

This data is updated as new photography becomes available – typically every 5 years.

Monitoring history

This data is updated as new photography becomes available – typically every 5 years.

Measurement technique

Waikato Regional Council's GIS was used to overlay properties in the Core Record System (CRS) with the coastal hazard areas. Locations of dwellings were also marked individually from aerial photographs to allow analysis of the number of dwellings within these hazard zones. In the most recent update of data (2017), the existing LINZ dwellings layer was used to identify the location of dwellings in the Waikato and Waitomo Districts. 

Coastal hazard areas were overlapped on top of the Core Record System (CRS) in the GIS to identify the properties that intercept the two coastal hazard areas.

The proportion of each property overlapped by the hazard areas was calculated to define the significance of hazard to the property as minor (<10%), moderate (10 - 30%) or major (>30%).

Where the proportion of a property within a setback zone was minor, the way that the hazard will affect the use of the property was considered to be relatively insignificant and these properties were excluded from the total count.

Using orthorectified aerial photographs (2003, 2007, 2012 & 2017) the most seaward point of each beachfront dwelling on the Coromandel Peninsula was marked in the GIS and compared with the hazard areas to calculate the number of dwellings at risk. On the West Coast where this indicator data is being reported for the first time the 2017 LINZ “buildings” layer was used to identify the location of existing dwellings.  This layer was adapted by filter out small buildings such as water tanks and garages. 

Results are summarised here for the Coromandel Peninsula and the West Coast. It is important to note here that there is currently no long-term coastal hazard area defined for the western coast of the Coromandel. Reported figures for this coast relate only to the current coastal hazard on the western Coromandel. Properties at risk under current conditions are included in the total values for the long-term risk area.

Coastal hazard areas are reported here in developed areas.  Rural properties and dwellings are not included in these numbers as hazard areas have only been defined for existing settlements.

This indicator is created using coastal hazard zones identified in three separate coastal hazard studies undertaken between 2008 and 2020. Data for the west coast of the Region is sourced from two recent coastal hazard assessments undertaken for the Waitomo and Waikato District Councils.

Coastal hazard areas on the Coromandel Peninsula: Dahm & Munro, 2009: Coromandel Beaches – Coastal Hazards. Review of Primary Development Setback at Selected Beaches. Report prepared by Focus Resource Management Group for Thames Coromandel District Council. October 2009.

Focus, 2020: Waitomo District Council Coastal Hazard Assessment. Prepared by the Focus Resource Management Group for the Waitomo District Council. October 2020.

Focus, 2020: Waikato District Coastal Hazard Assessment. Prepared by the Focus Resource Management Group for the Waikato District Council. February 2020.

Where the overlap is less than 10 per cent, the affect is recorded as minor on that property and these properties were removed from the graphed reporting. This indicator therefore only reports the number of properties where at least 10% of the total property area is within the hazard zone.  Small changes in the cadastre over time has affected properties that are “in or out” in relation to these criteria, so small changes in property numbers should be interpreted with caution as they may not represent genuine change.

Not all properties or dwellings within the hazard areas are exposed to the same level of risk and the risk depends on the exact location of the property or dwelling. For example, there may be a relatively high risk of erosion for dwellings near the seaward boundary of a hazard area but a very low risk from erosion to dwellings further landward.

There are small safety factors included in the coastal hazard areas, which reflect uncertainty and data limitations, and provide for a small buffer of land between a dwelling and the sea following the worst expected erosion. Therefore, some dwellings that lie only just inside the hazard area may be actually at very low risk of erosion but could be at risk from instability or unforeseen extreme events.

There is no setback to provide for the effect of sea level rise on beaches on the western coast of the Coromandel Peninsula. While erosion risk is likely to increase with sea level rise, the most significant increase in risk to coastal development on the western Coromandel Peninsula would be from coastal flooding associated with sea level rise.

The coastal hazard areas for Waitomo and Waikato have been defined as part of the District Planning process. These areas have been publicly notified but are subject to change during the hearings process. At this stage, these hazard areas must therefore be considered as draft.

There are some properties that contain more than one building that appears to be a dwelling. For the purposes of this indicator, secondary buildings were included if they are larger than 50 m², and not obviously a garage or other unoccupied/attached building. Temporary accommodation such as cabins in campgrounds were not included in dwelling counts.

This indicator will be updated as new aerial photography becomes available and will use the most up to date version of the Properties Database at the time of analysis (or as relates to the date of the photography.

• The dataset was checked for accuracy.
• Positional data loaded into GIS was checked for errors in map reference records.
• Buildings were checked manually over aerial photography.

There are 326 properties that are within the identified current coastal hazard areas on the east coast of the Coromandel Peninsula in 2017.  Out of these properties there are 176 dwellings at risk.  With future sea level rise the number of properties at risk could increase to 658, with 538 of these properties defined as dwellings.

There are 42 properties that are within the identified current coastal hazard areas on the west coast of the Coromandel Peninsula in 2017.  Out of these properties there are 28 dwellings at risk.

There are 155 properties that are within the identified current coastal hazard areas on the west coast of the Waikato Region (Waikato and Waitomo Districts) in 2017.  Out of these properties there are 90 dwellings at risk.  With future sea level rise the number of properties at risk could increase to 626, with 563 of these properties defined as dwellings.

There are no clear trends in risk between 2002 and 2017.