Extensive work to repair erosion caused by storms at popular Northland surf beach Sandy Bay is under way.

There are two main parts to the work - digging a new channel to redirect a stream and encouraging revival of the sand dunes.

The Whangarei District Council has erected a sign in the carpark at the popular surf beach, explaining to beachgoers the work which will be carried out over the next few months.

A stream used to flow north along the beach and exit with another stream at the end of a large sandspit that lay between it and the sea.

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Heavy storms washed a gap through the dune near the centre of the beach which changed the course of the stream. Sand to the north of the stream built up and prevented the stream from moving back to its original course.

These changes allowed the sea to wash in and out of the mouth of the stream, eroding its southern banks.

As part of the works, the stream will be dredged and sand will be placed on the foreshore and dunes.

The other main feature is large logs which will be anchored into the sand in certain locations to provide a natural shield against the waves.

The logs will have an auger system, like a giant corkscrew, attached to the bottom of them which will go about 2m into the ground, and can be moved if required.

The log wall will be altered as necessary over the coming years to minimise the problems caused by breaches during storm events.

A large dune near the public toilets will also be restored using some of the sand removed from the channel. The area will also be fenced off, some planting done and new paths on to the beach will be created.

The council sign said the dune will be rebuilt to its original height over time.

Opus is carrying out the work for the council. It should be finished in October.

Local resident Kiley Pullman said a pile of logs was delivered to the beach on Monday and major sand moving started on Thursday.

Sand from the northern end of the beach was being put on a trailer and driven by tractor down the beach to where it was being dumped near the dunes.

She said the stream had quite a few change over recent times and the bank had become very steep.

"I quite like the idea of restoring the dune and doing some planting."

Long-time local resident Malcolm Pullman said the beach was reaching its visitor capacity.

"What they've lost, if they get some of that back and the stream doesn't duck off and annoy anyone else we've won - and the surf break stays the same or improves."