The Tilby and Wairoa channels in Tauranga Harbour are being closed because they are too shallow for larger boats.

The channel marker poles near Ferguson Park and along the west of Matua will be removed because the channels are no longer navigable, says Bay of Plenty Regional Council deputy harbourmaster Chris Isherwood.

Channel markers are to be pulled from the Wairoa and Tilby channels.

The channels are the Wairoa River channel to the deeper harbour water, which runs from the river mouth and along the Matua shore, and the Tilby channel, which lies to the north-east past Ferguson Park.

'At high tide there's much less water where the channels meet with the main harbour than there used to be, and boats won't be able to get in or out at low tide,” says Chris.

'People could find themselves grounded very quickly.

'Small boats can still use the channels, but very carefully and preferably not on an outgoing tide.”

The silting is a natural occurrence and the channels could eventually become navigable again, says Chris. It is caused by erosion of soil from surrounding land and tidal currents from other parts of the harbour.

While the river mouth could be dredged, it is expensive. The Regional Council is working with land owners to manage land use to protect waterways and native bush while keeping the land productive.

'The Regional Council supports this approach by providing advice, and in some cases funding, to fence waterways, plant trees and control pests,” adds Chris.

Signs warning of the shallow water will be erected near boat ramps in the area.