Ocean And Community Dynamics At Play In Dune Restoration
It’s just not the dynamics of the ocean that needs to be considered when dealing with coastal erosion – the dynamics of community are equally as important.
Coastcare Waikato, a partnership between local communities, iwi, district councils and Waikato Regional Council to protect and restore the region’s coastlines, has this year undertaken its largest dune restoration project, along 700 metres of Whangamatā shoreline that was badly eroded by Cyclone Gabrielle.
The cyclone removed much of the dunes at the south end of the beach, increasing the exposure of 30-plus properties to future storms and big swells.
Neil Richardson, one of the many homeowners anxious about the future of their coastal property, says quick action was needed to address the exposure, and conflict would have been inevitable without agreement on a working plan to move forward.
“Conversations and compromises were needed right at the start,” says Neil. “All the usual questions arose. What should be done? Who is responsible for the work? Who pays? How will any work achieve the multiple goals of the residents, local and regional council, local iwi and other vested parties. How do we achieve a long-term solution for the whole beach, rather than just for individual properties?
“Happily, the experience has been an extremely positive one.”
Coastcare coordinator Andy Warneford, who works with communities between Tairua and Whiritoa, says the landowners approached Thames-Coromandel District Council wanting a solution.
“Of course, they talked about sea walls, but we managed to steer them in the direction of giving a soft coastal method a chance to show what can be done.”
Coastcare Waikato had already successfully restored a number of beaches in the Coromandel Peninsula with a soft engineering method known as a ‘whole of dune approach’, for example, at Kūaotunu, Tairua, Greys Beach and Cooks Beach.
“People were understandably pretty stressed out. That is the Pacific Ocean there 20 metres away from their home and they have a towering escarpment right on the boundary of their property.”
The whole of dune approach involves spraying and removing remaining exotic vegetation along the top of a dune, burying it, and reshaping the dune to the correct gradient using earthmoving equipment and beach sand. The newly created dunes are then planted with native kōwhangatara/spinifex and pīngao to trap the sand and allow them to naturally rebuild after storm events.
“Usually, a 200-metre restoration project is considered quite chunky,” says Andy. “But in Whangamatā, we did 750 metres of almost continuous restoration in front of about 40 houses.
“Sand dunes give protection to the land behind them; they act as a buffer against eroding wave action. The dunes at Whangamatā fluctuate dynamically landward to seaward, however, the recent years of La Nina have meant the dunes in some places are at their most landward since 1944.
“By doing dune restoration, we create more sand for storms to take away – instead of land or infrastructure.
“At Whangamatā, we had a resource consent to go down to the mid beach and grab the sand from there and put it back up on the dunes.”
It took two diggers and a tractor trailer unit three weeks to fully restore the eroded dunes, and a big part of recreating a dune system is putting in the right plants and giving it some time.
“The pīngao and spinifex help build the dunes seaward by trapping and holding sand. We get rid of plants that don’t help accretion: agapanthus, gazanias, ice plant, couch grass, lupins, kikuyu, bushy asparagus. People see these weeds in a dune area and think they are holding the dune together, but they aren’t, and they aren’t helping with accretion. If you have accreting plant species, and calm conditions, the dunes will build seaward for free.”
Andy says it amazes him that many people still want rock walls to prevent coastal erosion.
“You can’t stop erosion, but soft protection measures – like a sand dune – do absorb the energy of the sea better than hard protections methods. Hard protection methods, like seawalls, deflect wave and tidal energy to property or infrastructure, which can create and affect erosion.
“Have you ever noticed that your feet sink in the sand where the waves start to retreat? That’s because the waves are eroding the sand under your feet. That is exactly what happens in front of a sea wall, and that process will end up lowering the beach and reducing beach access.”
The new dunes, now in place, are doing their own advocacy with neighbouring landowners.
“Overwhelmingly, people are happy with what we have done. It looks amazing! I’ve even had one guy who wasn’t into it at all come up and shake my hand and plead for us to do it in front of his place.”
The Whangamatā dune restoration was supported in favour of other forms of coastal protection by all but one adjoining landowner. The landowners contributed funding towards the project, which allowed Coastcare Waikato to widen the area of dune restoration. Plants were supplied by Thames-Coromandel District Council and Waikato Regional Council and planting bees were attended by the landowners and the local schools.