Disaster and recovery in the Ōtaki dunes

JL16_erosion-june-16-3_F.jpgIn June three years back, a severe natural event struck the north end of Ōtaki Beach.

Extreme high tides surged up the already flooded Waitohu Stream, which caused the stream to cut across the beach to the south. This took out a huge swathe of dunes, leaving a steep sand cliff lapped by the sea in their place.

Locals were dismayed, especially the volunteer workers of the Waitohu Stream and Dune Care Group. “We were very distressed about the amount we lost,” said group chairperson Sue McIntosh.

“Since 2003 our group has been working to build up the dune system on the south side of the stream and it had gone from a bare desert, ground down by vehicles, to rolling dunes planted with the native dune-grasses, spinifex and pingao. “Almost overnight a huge swathe of this vanished. A crumbling cliff stood in its place and plants lay all over the beach. There had been earlier events, with high tides, storms and dune erosion, but nothing on this scale.”

Three years on, however, the cliff has mellowed to a shallow slope and spinifex roots left exposed by the erosion are gradually taking hold and rebuilding the dunes. Driftwood which piled up naturally in the eroded area accelerated the sand build-up.

“We want people to think twice before they take driftwood from the beach,” said Sue. “It’s part of this natural cycle of erosion and accretion and plays a huge part in restoring the dunes as a buffer between the sea and land. “We’re amazed how quickly the dunes have rebuilt, thanks to the driftwood and all the earlier spinifex plantings.

Before this work started, the dunes, if any, were formed around marram, an introduced grass which doesn’t have the long sand-binding roots of our native plants, so the dunes quickly erode and wash away.”

Stream-Care-logo_F_RThe Waitohu Stream and Dune Care Group

The Waitohu Stream and Dune Care Group was formed in 1999 in response to the degraded state of the Waitohu Stream, at that time said to be the most polluted stream in the Wellington region.

In 2000 the group built its own nursery and planted hundreds of native seedlings to stabilise the stream banks and improve the habitat for native stream life.

The Wellington Regional Council “Take Care” programme funded the group and KCDC also assisted . In 2003, when the group’s focus moved from the stream and the estuary to rebuilding the dunes, KCDC dragged enormous logs to plug gaps in the dunes and provide a starting point for sand build-up.

The group began planting on the emerging dunes, using locally-sourced spinifex seed to grow the plants in their own nursery. Then the rabbits moved in and started to destroy young plants. The group now protects vulnerable plants from rabbits and the WRC helps with their control. Protecting the plants from humans is another big issue. “We use a series of light stakes connected by tape to keep people and vehicles off the young plants on the dunes,” said Sue. “This works quite well and as the dunes grow we have moved the barrier west several times.” The group is always keen for new volunteers.

Family planting and sausage sizzle July 23rd

On July 23 at 10am all are invited to a special family planting day followed by a sausage sizzle, along with Forest and Bird’s Kiwi Conservation Club.

Mondays 9:30am every week

The group’s regular work day is Monday morning, starting at 9.30 in winter, 9am in summer, with morning tea around 10.30am. The group gathers at the nursery at the north end of Moana Street, opposite number 14.

For more information, email autaha@actrix.co.nz or ring Sue at 364 0641.