Water always find its way, as the lie of the sand on a popular Tutukaka surf beach proves.

Work carried out at Sandy Bay - at a cost of upwards of $70,000 - to shore-up eroding sand dunes and reroute a stream's outlet has been ripped apart for the second time this summer.

Whangarei District Council has admitted the ''soft'' remedial work was a failed experiment.

Since work late last year to repair the degraded bank and redirect the stream to the north end of the beach, two major easterly storms that coincided with king tides have undone the remediation attempt.

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Logs and chains meant to catch sand and create new banks are now exposed and floating in the shallow stream. The recently formed banks have been chewed away by high tides and stream volume.

A wooden slat retention fence, intended as a sand trap to help create dunes in front of the bank above the beach, is also exposed.

The council has invited coastal engineer and dune expert Andre Labonte to review the situation and make recommendations.

Mr Labonte said trying to redesign nature's course and modify the ocean's effect on environments already affected by people was ''challenging''.

''One of the challenges at Sandy Bay is that it is so heavily used all year round, because you have to manage public access,'' he said.

Mr Labonte said Matapouri Bay's northern remediation was an example of new dunes holding better if revegetated as well, and boardwalks on to the beach preventing dune grasses from being trampled.

Past modifications at Sandy Bay had not helped, he said. ''They make it hard to re-establish a permanent solution.''

He was unwilling to further comment as it would pre-empt his report.

WDC parks manager Sue Hodge said the council had consulted with the community about options to repair the dune erosion which caused the stream to run through the middle of the beach instead of along its previous course.

The community was keen for a "soft" engineering solution to better fit with the landscape and environment that makes Sandy Bay so popular.

The logs-and-chains option was trialled rather than a hard-engineered, permanent and highly visible option like rock revetment wall.

Hutton and Cameron did the $70,000 sand remediation work last year to a design by Opus. At the same time $219,000 was spent on the carpark.