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Regional Council aims to reduce erosion risk at Maketu Spit

Friday, 20 December 2013 10:00 a.m.

Bay of Plenty Regional Council is hoping to reduce the risk of erosion at Maketu Spit, using work planned as part of its Kaituna River Re-diversion and Wetland Creation Project.

Project Manager Pim de Monchy said the Regional Council was aware of the risk and was considering how it could be reduced while investigating and planning the re-diversion works.

“In recent years the spit has been narrowed by erosion opposite Whakaue Marae, to the point where there is a risk of the spit breaching during a large storm and opening up a second estuary entrance about 700 metres west of Maketu Surf Club,” he said.

“The erosion risk increased in 1956 as a direct result of diverting the Kaituna River at Te Tumu, which caused the lower estuary to fill in with sand. If the spit breaches it would cause significant disruption to channels and navigation within the estuary and over the bar. It would also disrupt habitat for threatened shorebirds and probably add to the amount of coastal sediment deposited in the estuary for a period of time.”

Similar breaches had occurred in the past since the Kaituna River was diverted away from the estuary in 1956, most recently between 1994 and 1999, he said.

“The Kaituna River Re-diversion project has been established to partially re-divert the river into Maketu Estuary, which will reduce the risk of future spit breaches and improve navigation in the lower estuary.

“There is little that can be done to prevent a spit breach now, so the emphasis is on designing and implementing the long-term solution as soon as practicable. The preferred option for the project will increase the amount of Kaituna River water entering the estuary from 5 percent to 20 percent and help to flush out some of the built up sand.

In addition, the project will create at least 20 hectares of new wetlands and re-connect parts of the estuary which are currently isolated by old stopbanks.”

“Modelling is being done which will, among other things, examine the effectiveness of the diversion as a permanent fix in the longer term, as well as examining any shorter term concerns. 

He said once the long-term solution was implemented, the erosion pressure on the spit would reduce, and scour of the flood tide delta or sand banks within the estuary would slowly improve channel depths, leading to improved navigation and potentially better shellfish habitat.

Work on the project could start in the summer of 2015/16. Find out more at www.boprc.govt.nz/kaitunamaketu

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Kaituna Spit erosion small