Marawhara 18 December 2011

On Thursday 15 December a number of local groups met with the Auckland Council’s Local and Sports Parks West, Auckland Transport and the Waitakere Ranges Local Board to discuss the vexed question of the Marawhara and Wekatahi Streams. Piha Coastcare has been keen to see the streams separated to protect dune plantings carried out several years ago which are being eroded as the Marawhara has migrated south and joined with the Wekatahi.

Parks’ view, supported by the Auckland Council’s coastal team and local groups, has been that unless the streams are threatening the road, which was the reason they were separated, there is no cause for immediate action and a “wait and see” policy is prudent.

Coastal processes are dynamic, streams change course and dunes build up and are eroded away by waterways and high seas. Coastal streams flowing down to the sea are behaving differently with the lighter rainfall this winter. At Karekare the flow in the stream has not been augmented by flood events and has formed a deep lagoon, impounded by large amounts of sand that have shifted down the coast from Whatipu.

This Thursday’s meeting where Coastcare, Piha R&R, and Waitakere Ranges Protection Society met with a dune expert from the Council’s Land and Coastal Processes , as well as Parks, Biodiversity and Research Investigations Monitoring staff, was tasked with agreeing on trigger points which if reached by erosion would prompt the Council to look at action.

The agreed trigger line along the dune will be monitored by the Council and locals. The proposed trigger alignment is 1-2 metres north from the first dip in the dunes from the road. This is about 15 metres back from the edge of the current stream bank. At this point the road is not under threat.

The beach will be monitored and a report made in January. Meanwhile, this week’s very heavy rain the Marawhara started to break through the sand to go on a straighter course to the sea but this has not lasted.