Shoreline protection structures

Why we monitor shoreline protection structures •
What's happening? •
Methods - how we monitor •
Results - data and trends •
Download the data file •
When this indicator is updated

Why we monitor shoreline protection structures

A large portion of the Waikato region’s sandy coastline has become intensively developed, particularly on the Coromandel Peninsula. In many cases, this development has occurred very close to the shoreline, leaving insufficient area between the development and the sea to protect from processes such as natural coastal erosion and future sea level rise. Shoreline protection works are built along the coastal margin when the sea threatens property or infrastructure.

Shoreline protection structures can affect public space and the local environment. In some circumstances, shoreline protection structures can severely degrade the quality of the beach. Waikato Regional Council (WRC) therefore needs to know where shoreline protection structures have been erected and how they affect this region’s beaches and coastline areas. The presence of shoreline protection structures also reflects the degree to which shorelines and coastal developments in the region are under pressure from natural phenomena such as ongoing sea level rise and storms.

WRC has responsibilities for the regulation of shoreline protection structures within its coastal marine area (CMA) under Section 30 of the Resource Management Act (RMA), and the Regional Coastal Plan (RCP).

This indicator will help WRC to monitor pressure on the regions shoreline and whether regional policy and plans are appropriately addressing the issues involved.

Only a small proportion of the existing coastal protection structures are consented through the RMA, or previous legislation. This indicator reports observations of structures in the field, as well as considering the number of legally established structures.

Shoreline protection structures affect:

Natural character: The natural qualities of our coastal environment are called natural character. These include natural processes, and the spiritual, cultural, scientific and visual values of our coasts. The natural character of our beaches is important to people in the Waikato region. It is recognised as a matter of national importance in the New Zealand Coastal Policy Statement. Adding foreign material to our coastal areas and preventing altering natural landforms and processes can degrade their natural character.
Natural processes: People build shoreline protection structures to stop erosion of the land. While groynes can protect dunes by holding sediment in place, they can increase erosion elsewhere if trapped sediment is unable to reach neighbouring beaches. Seawalls can stop dune erosion, but often at the expense of lowering the level of the beach in front of it, so the dry sandy beach is lost at high tide. There can be increased erosion at either end of the seawall where increases in turbulence occur near the ends of the wall (‘end effects’).
Public values: The effects of structures on natural processes and landforms can make access to the beach and along the beach difficult. Large, poorly designed, or unstable structures can be unsafe (particularly for young children and the elderly). Often alternative public access needs to be created.

It is therefore important that shoreline protection structures are:

only built where necessary, and
managed so that their adverse effects can be avoided or reduced.

What's happening?

The Waikato region has about 1,150 km of open coast and estuarine shoreline. There has been considerable urban development in some areas, particularly on the Coromandel Peninsula. Much of this development has occurred close to the shoreline. This means there is not enough space left between the development and the ocean to protect against coastal erosion or the effects of predicted sea level rise.

Shoreline protection structures are more likely to be built in areas where private property is exposed to these coastal hazards. This means our more highly developed beaches tend to have a greater number of protection structures. These structures can affect our coastline’s natural character and make access to our beaches difficult.

Methods - how we monitor

Monitoring sites
We surveyed shorelines throughout the Region during the field survey. We also reviewed consented structures using WRC’s consents database.
Monitoring frequency
The next survey is planned for 2030 and will be repeated every 10 years.
Monitoring history
The initial survey was for this indicator undertaken during December 1994 and January-March 1995 and included a field assessment of all coastal structures (both consented and non-consented) in the Waikato Region. This field survey was repeated in stages over the summers of 2015/16 and 2016/17. These surveys covered the majority of shoreline in the Waikato Region, but there are gaps in coverage.
WRC also records the number of coastal protection structures that currently have resource consent. Data on both existing and consented structures is presented in this indicator.
Measurement technique
- Data was collected using a handheld device. All structures within the coastal marine area were recorded by collecting a GPS coordinate and basic descriptive information (type, material, condition). Photographs of all structures were collected with a digital camera.
- Surveys were mainly completed by foot. In some locations foot access was impractical or impossible. Some estuarine areas were surveyed by boat and some estuarine and open coast areas were surveyed by helicopter.
- Consented structures are identified through WRC’s consents database.
Existing structures have been identified in a series of field surveys. This data was compiled from several surveys into one dataset and filtered to identify the locations of the structures.
Consents for coastal protection works were filtered from all coastal permits and separated into coastal zones, to provide summary statistics on the number and distribution of shoreline protection structures for three areas, the west coast of the Waikato region, and the eastern and western coasts of the Coromandel Peninsula.
None relevant to this indicator.
There are some locations that were not surveyed in the latest field survey due to time constraints or inaccessibility.
Consented structure data included in this assessment is limited to consented structures recorded in the Regional Council’s database. Some older structures may have been consented under older legislation. There may be some structures identified in the field surveys that are located above mean high water springs and have consent with the relevant District Council and therefore are not consented by WRC. Expired consents are also not recorded.
The following improvements to data collection and analysis are intended:
- Consider incorporating consents for other related activities, such as beach scraping, beach renourishment, backstop walls (District Council consents) and, where possible, activities associated with managed retreat.
- Provide further breakdown statistics by location if required.
- Consider authorisations that have expired, which are not currently reported under consented structures.
- Gather structure consent details from the District Councils.
Data provided from the consents database was checked as far as possible to ensure that it accurately reflected known consented coastal protection structures.

Results - data and trends

The graphs below show the number of existing shoreline protection structures in the Waikato region, and the number of currently authorised structures.
A survey of existing structures in 2015-2017 recorded 465 coastal protection structures in the Waikato region. This a small reduction in the total number of structures since 1994/5, but this may also reflect gaps in the dataset, as there were still some areas not covered in the more recent survey.
There are a total of 156 consented coastal protection structures in the Waikato region in 2020. When this data was reported in 2011, only 38 authorised structures were identified. Overall consenting records indicates that 118 coastal protection structures have been authorised since 2011.
It is important to note that this does not necessarily reflect an equivalent increase in the actual number of existing structures. The field survey of existing structures does not indicate that the actual number of existing structures has increased significantly. Instead, many structures previously unauthorised, or that may have been missed in the 2011 study are now consented. Increases in consented numbers is at least in part due to ongoing efforts to authorise existing structures, including many seawalls on the western Coromandel, and on Kawhia Harbour shoreline. Some of the “new” consents reflect maintenance or replacement of existing (previously unconsented) structures.
This indicator indicates that in 2011 only a small proportion of existing structures hold any form of official permit or consent. In 2020 there are more structures with current consent but this is still only approximately one third of all existing structures.
This indicator over time will reflect erosion pressure on development or infrastructure located next to the coast. When compared with data from field surveys of existing structures, it also provides insight into the proportion of structures that are now being managed under some form of resource consent.