Talks look at gravel management plan
Scattered gravel extraction, ripping river beaches so they can be shifted by floods and information gathering on the district's rivers are all part of Tasman's new river gravel management plan.
Broad details of the management plan were circulated at the council's fourth gravel management workshop, held in Motueka on Tuesday evening.
Councillor Jack Inglis asked why gravel was not being taken from under the Motueka River bridge to lower the level of the river and reduce the risk of flood damage, but council rivers asset engineer Philip Drummond said silt and gravel had only built up on the banks of the river. The riverbed had been degrading for years and there were about 300 square metres of water capacity under the bridge.
The built-up silt and gravel was earmarked for use in the upgrade of the Motueka sewerage ponds and the Lower Motueka stopbank project.
It was no use lowering the riverbed to below sea level. Even a flood could not push the tide out, he said.
Arthur Walker, of Motueka, said he thought the council was "cleaning out" the Motueka riverbed before rebuilding the stopbanks.
Council transportation manager Gary Clark said the extent to which extraction reduced flood risk was minor. Taking a metre of gravel out of the river's gravel beaches would lower the top of a one-in-100-year flood by only 300 millimetres, he said.
Chief executive Lindsay McKenzie presented a paper summarising the council's approach to gravel management in rivers and the conflicting and competing uses for gravel, both in stream and for extraction.
The gravel-extraction policy was based on part IV of the Tasman Resource Management Plan, decisions on which were released last year.
The plan allowed gravel to be relocated, where it was causing problems, managed within its beds and extracted where localised buildup occurred, and set some sustainable extraction limits.
The proposed river gravel management regime is open for public feedback until late January. See tasman.govt.nz/link/gravel-management.
- © Fairfax NZ News
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