Collaroy storm damage

WRL coastal engineers document the worst erosion at Collaroy since 1974

WRL manages one of the world’s longest-running beach erosion research programs, at Narrabeen-Collaroy on Sydney’s northern beaches. Such long-term measurements of coastal variability are extremely rare and provide a unique insight into beach variability at different scales – from rapid erosion caused by extreme storms to changes over years and decades due to more subtle shifts in the wave climate.

Last week WRL coastal engineers had the amazing opportunity of documenting the worst erosion event observed at Collaroy since 1974. WRLs team of coastal forecasters monitored an extreme event emerging on the horizon as early as six days prior the June 4th East Coast Low event. This early forecast enabled the team to collaborate with the NSW Office of Environment and Heritage and UNSW Aviation to mobilise unprecedented coastal monitoring capabilities and capture rare high-resolution observations of how coastlines evolve during extreme events.

Changes in cross-section measured at Narrabeen Beach as part of the long-term coastal monitoring program. An incredible 50m shift in beach is observed over just 3 days due to the storm event.

40 year time-series of beach sand volume at Collaroy. Following the storm, the beach is now in its most eroded state since measurements begun.

Pre and post UAV (drone) surveys at the section of Collaroy Beach hardest hit by the June 2016 East Coast Low.

Pre storm data collected by the WRL coastal team and collaborators include:

  • Shoreline positions measured remotely every 30 minutes by the of Narrabeen-Collaroy coastal imaging station;
  • Airborne LiDAR surveys at 20 critical and sites located between Sydney and Coffs Harbour (undertaken four days prior to storm by the UNSW School of Aviation);
  • High-density UAV (drone) point-cloud data of the entire Narrabeen-Collaroy embayment, including the dunes and beach face;
  • RTK-GPS cross-shore profiles at long-term monitoring locations (Narrabeen-Collaroy, Bilgola,  Mona Vale  and Dee Why);
  • Three-dimensional survey of the entire Narrabeen Collaroy embayment using an All-Terrain-Vehicle mounted with RTK-GPS;
  • High-frequency LiDAR scans of a single transect located in front of the Flight Deck Building at Narrabeen;Offshore bathymetry measurements using a jet-ski at Narrabeen-Collaroy, Bilgola and  Mona Vale beaches (undertaken by the NSW Office of Environment and Heritage); and
  • Nearshore deployment of WRL’s mini waverider buoy by OEH in 10m water depth in front of the Flight Deck Building at Collaroy.

During the storm event, WRL’s coastal monitoring team were quick to utilise all available datasets for real-time assessment of the rapidly evolving beach conditions. When the extreme conditions subsided, it was found that the beach shifted an incredible 50m in width due to the storms, which is the most eroded in 40 years of measurements.

The unique data collected by the WRL team in collaboration with UNSW Aviation and the NSW Office of Environment and Heritage will provide invaluable insights on how beaches evolve due to extreme events and will help fine-tune the tools coastal practitioners need in order to help manage events like these in the future.

Drone footage of severe coastal erosion on Sydney's Northern Beaches

Drone data of Collaroy after the June 2016 east coast low

Narrabeen Coastal Imaging - Timelapse of the June 2016 Storm Event

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