Dunes are narrow but important areas of sand that lie between the sea and the land. Dunes and their native plant communities are part of the natural character of our distinctive New Zealand coastline.
Dunes protect properties against coastal erosion and flooding from waves. They:
- provide a physical barrier against storm waves, reducing the risk of flooding for nearby properties
- work as a dynamic buffer, and are eroded and then built up again as part of natural physical processes.
However, when these natural processes are interfered with, our coastline becomes more exposed to coastal hazards such as storms and flooding.
There are two types of coastal erosion:
- Short-term erosion – This can be caused by storms or climate cycles without causing a permanent change in the position of the shoreline. While the area usually recovers, a full erosion and recovery cycle can take several decades.
- Long-term erosion – This is when there is a permanent change to the position of the shoreline, for example, through erosion caused by sea-level rise.
Sand-binding plants play an important role in the formation, development and maintenance of dunes. If dune plants are destroyed, eventually the dunes themselves can be lost, leading to severe damage to the beach and risk to coastal properties.
- native sand grasses on the seaward face of the foredune
- larger and more diverse shrubs and trees inland.
There are two main native sand-binding plants:
- pingao (golden sand sedge)
- spinifex (silvery sand grass).
Planting pingao and spinifex begins the process of dune succession which results in dune stabilisation and the later establishment of larger plants either by planting or introduction of seeds by birds.