Shoreline protection structures
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 when the sea threatens property or infrastructure.
Waikato Regional Council needs to know where shoreline protection structures have been erected and how they affect this region’s beaches and coastline areas. This is because shoreline protection structures can affect public space and the local environment. They also reflect 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.
Other responses to this kind of pressure not currently incorporated into this indicator include beach renourishment, beach scraping and managed retreat of housing and infrastructure from the shoreline, and we are therefore also considering incorporating these into the indicator as they occur.
Waikato Regional Council 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 proposed Regional Coastal Plan (RCP).
This indicator will help Waikato Regional Council to monitor increasing pressure on the regions shoreline and whether regional policy and plans are appropriately addressing the issues involved.
Shoreline protection structures affect:
- Natural character: The natural character of our beaches is important to people in the Waikato region. Natural character includes natural processes, and the spiritual, cultural, scientific and visual values of our coasts. It is recognised as a matter of national importance in the New Zealand Coastal Policy Statement. Adding foreign material to our coastal areas can degrade their natural character.
- Natural processes: People build shoreline protection structures in an effort to stop dune erosion. 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: Structures can make access to the beach difficult, and large, poorly designed or unstable structures can be unsafe (particularly for young children and the elderly). Often alternative public access needs to be created.
Therefore, it's important that shoreline protection structures are:
- only built where necessary, and
- managed so that their adverse effects can be avoided or reduced
The Waikato region has about 1,150 km of open coast and estuarine shoreline. There’s been considerable urban development in some areas, particularly on the Coromandel Peninsula. Much of this development has occurred very close to the shoreline. This means there isn’t 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.
More detail on this indicator, including how and where Waikato Regional Council collects this information, is available in the Technical Information page.
When this indicator is updated
The indicator will be updated and republished every 2 years. The next update is planned for 2013. Contact at Waikato Regional Council\
Contact at Waikato Regional Council
Coastal Scientist - Science and Strategy Directorate