Water and sediment may swamp towns

By TONY GEE

KAIKOHE - Many Far North towns and settlements face a serious risk of either being buried by sediment or flooding out, says a Northland Regional Council discussion document.

Elsewhere farmland is being eroded away by streams and their rising beds are lifting watertables, turning some farming areas into swamp.

"Given the threat of high intensity rainstorms almost anywhere within the Far North district, there is a high potential for serious flood damage to farmland, dwellings, industrial sites, roading and other infrastructure and to significant population areas on floodplains and in harbours and estuaries," the report says.

The paper, considered by the Far North District Council at a meeting last week, was commissioned by the regional council to help the authorities develop river management policies.

It also aims to establish priorities for undertaking river works in the wake of confusion in Northland about which body is responsible for river management, after last year's heavy flooding in Hokianga, Dargaville and Whangarei.

An author of the report, regional council land operations manager Bob Cathcart, says it is neither practical nor financially possible to expect the regional or any district council to be able to stop the flooding.

Where river works have been carried out in the past they attracted substantial financial subsidies from the Government, but these subsidies are no longer available.

"It is beyond the resources of any single council in Northland to fund river management to prevent all flooding."

The river management policy objective needs to ensure that river channels carry their normal flows.

When rivers overflow their banks, the policy should result in minimal damage to agriculture, infrastructure and buildings.

The report calls for river management work to focus on the removal of willow trees, accumulated gravel and other obstructions to water flow, and for the restoring of river channels. It also says regular river maintenance programmes need to be set up.

"Unless there are very valuable assets under threat, anything more elaborate would be financially unsustainable."

The document identifies specific flooding threats posed by 18 major rivers and streams, including the Awanui (Kaitaia), Wairoa (Herekino), Taipa (Peria and Oruru), and the Kaeo, Panguru, Waima, Otaua, Whirinaki, Waihou, Mangamuka, Waitangi and Kawakawa.

Should existing debris blockages in upper valley streams build up against a bridge or trees growing in the river channel or banks, and then suddenly burst free, there is potential for serious damage to property and infrastructure in Kaitaia and even loss of life, the report says.

It also identifies that a large slump is moving into the Awanui River from Bell's Hill, immediately to the east of the town.

If the rate of movement of the slip increases there is the potential for it to suddenly move and block the river when it is in flood.

This would divert floodwaters into the centre of Kaitaia and "could happen so quickly that warnings could not be issued and lives could be lost."

The report recommends a joint regional and district council working party be set up to prioritise river projects.

Discussions are continuing between the two councils, but final decisions will not be made on which rivers are to be worked on this year until both have confirmed their river management budgets.

Meanwhile, both councils have formally sought to uplift the Government's promised $250,926 contribution to flood protection work in the four Hokianga communities devastated by flooding in January last year.