Northern beaches smashed by 1 in 10 year storm

A ONE in 10-year downpour that dumped more than 100mm of rain over the northern end of the peninsula in just three hours forced authorities to open Narrabeen Lagoon to the ocean.

A ONE in 10-year downpour that dumped more than 100mm of rain over the northern end of the peninsula in just three hours early Tuesday forced authorities to open Narrabeen Lagoon to the ocean.

Northern Beaches Council called in a digger and bulldozer to cut a 70m channel through North Narrabeen Beach after concerns grew that the deluge would cause flooding in low lying streets around the lagoon.

Residents had been complaining to council for several weeks about rising water levels and that something must be done to immediately release the water.

Northern Beaches Council workers at North Narrabeen Beach preparing a channel to open Narrabeen Lagoon to the ocean

Areas around Warriewood and Mona Vale received the highest rainfalls with 112mm recorded at Mona Vale Golf Course between 3am and 6am.

Two-thirds of the course was covered in stormwater run-off up to 1.5m deep for most of yesterday.

The rain, which prompted a severe weather warning from the Bureau of Meteorology, was caused by a slow-moving low pressure trough that brought localised heavy rain to parts of the Sydney metropolitan area.

The council’s environment general manager Ben Taylor said the entrance to the lagoon was opened due to the heavy overnight rain.

A channel through the sand links Narrabeen Lagoon with the ocean. Picture: Jim O'Rourke

It had been closed since early January after large swells pushed sand across its entrance.

“The lagoon is normally opened when levels are between 1m and 1.3m above sea level,” Mr Taylor said.

“The lagoon is now at 1.1m above sea level and heavy machinery (was used) to open the lagoon.”

Council also said the downpour was a one in 10 year event for the northern beaches.

Mayor Michael Regan said council had been monitoring the lagoon so it could act as soon as the required level for a successful opening of the entrance was reached.

“Many councillors have been hearing from residents on this issue and working with council to ensure this was done at the right time,” Cr Regan said.

Mona Vale Golf Club's pro Gerard Kelly is hoping golfers will be back on the course on Wednesday. Picture: Julian Andrews.

Mona Vale golf course professional Gerard Kelly said he had never seen so much water on the course in his 27 years at the club. “It’s really disrupted things,” Mr Kelly said. “We had a big day booked today, including one group of 40 golfers, but we’ve had to close the course.”

A watery view from the 11th tee at Mona Vale golf course.

Course superintendent Sam Neylon said the flooding was mainly caused by run-off from Pittwater Rd.

“It collects here because we are the lowest point in the area,” he said.

Mr Neylon said he expected the course would be open today, but would not be playable until Saturday.

If members of the public have any concerns, please call the council’s customer service team on 1300 434 434.

For more information on Narrabeen Lagoon management click here.