Sand removed from Narrabeen Lagoon entrance to prevent flooding, replenish beachfront

A major excavation of sand near the entrance of Narrabeen Lagoon has begun as part of Northern Beaches Council’s ongoing management of the lagoon to reduce the risk of flooding.

Sand being removed from Narrabeen Lagoon east of the Ocean St bridge in 2018. Photo Manly Daily

A major excavation of sand near the entrance of Narrabeen Lagoon has begun as part of Northern Beaches Council’s ongoing management of the lagoon to reduce the risk of flooding.

The sand removed from the lagoon will be trucked south and used to replenish the Collaroy-Narrabeen beachfront.

Repairs to the abutments of the Ocean St bridge will be done simultaneously to minimise disruption to the community.

Major sand clearances from the entrance of the lagoon are conducted every three to four years, as swell and tides gradually push more sand into the lagoon.

Sand being removed from Narrabeen Lagoon west of the Ocean St bridge in 2018. Photo Manly Daily

The council completed the last clearance of the entrance of Narrabeen Lagoon in 2018 and has had to undertake more frequent mechanical openings in recent months as the sand has built up.

Works will be conducted using amphibious excavators to pump the excess sand through flexible pipes to a central stockpile location next to the carpark in Birdwood Park, from there it will be trucked south to Mactier St where a bulldozer will spread it along the Collaroy-Narrabeen beachfront.

Northern Beaches mayor Michael Regan said the works are an important part of managing the lagoon.

Removal of sand from Narrabeen Lagoon west of the Ocean St bridge in 2018. Photo Manly Daily

“It will reduce the risk of flooding to residents around Narrabeen Lagoon, replenish eroded areas further up the beach, as well as improve tidal exchange,” he said.

“Since we completed the last major excavations, waves and ocean swells have pushed sand back in and filled the entrance.

“Recent bathymetric surveys have revealed that tens of thousands of cubic metres of sand has returned to the entrance on the eastern and western sides of the Ocean St bridge.

“Once the major excavation is complete, the lagoon is expected to remain open for a number of years, although as always, we are at the mercy of mother nature as to how long.

Sand being dredged from Narrabeen Lagoon east of the Ocean St bridge in April 1979. Photo Manly Daily

The council says clearing the lagoon clearance and the bridge works will take around 12 weeks to complete, depending on the weather, with the lagoon expected to be reopened in mid-December in time for the holiday period.

It said that during the works, there may be minor traffic disruption near the Ocean St bridge and some periodic limits to access to parts of the lagoon entrance.

Children play on a sand pile near the entrance of Narrabeen Lagoon in 2011. Photo Manly Daily

The removal of sand from the entrance to the lagoon has become a regular occurrence in recent decades.

In 2016, 45,000 cubic metres of sand taken from the lagoon entrance was used to replenish the Collaroy beachfront in the wake of the serious erosion of sand in June that year.

The 2016 operation cost close to $1 million and saw about 100 truckloads of sand removed each day from the western and eastern sides of the Ocean St bridge between August and October.