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Welcome to Manly LagoonWatch

LagoonWatch is a real time rainfall and water level monitoring system for coastal lagoons that provides early flood warning and predictions as well as a cost efficient means of flood mitigation and potentially water quality management.

This management system has been developed by Manly Hydraulics Laboratory for Manly Council with financial and technical support from the Department of Environment and Climate Change.

Lagoon Processes

Manly Lagoon responds to tides, ocean surges, wave setup and rainfall. Real time data from instruments which monitor these processes is combined in a mathematical model which then predicts the water level for twelve hours in the future for three potential weather options. The model predicts water levels for three future environmental scenarios:-
  1. 100% Annual Exceedance Probability (AEP) - A typical rainfall event with a duration of nine hours and an intensity exceeded approximately once every year. This is approximately equal to a 1 year annual recurrance interval rainfall event.
  2. 50% Annual Exceedance Probability (AEP) - A typical rainfall event with a duration of nine hours and an intensity exceeded approximately once every two years.
  3. 20% Annual Exceedance Probability (AEP) - A typical rainfall event with a duration of nine hours and an intensity exceeded approximately once every five years.

Model Results

Manly Lagoonwatch Model Results

Real Time Data Collection Network

Catchment Rainfall

Four pluviometers providing real time rainfall intensities are located at:

Water Level

There are three automatic water level/water quality recorders in the catchment at:

Manly Lagoon Catchment Map

Click on the name of the station to view the data.
Click on the name to display data CROMER ALLAMBIE HEIGHTS NORTH MANLY BELROSE FRENCHES FOREST RIVERVIEW PDE. QUEENSCLIFF MANLY DAM CURL CURL DEE WHY CHATSWOOD BOWL.

Ocean Conditions

Ocean tides are provided from MHL's tide gauge in Sydney Harbour and the offshore wave climate is provided from MHL's Waverider buoy located 10km offshore from Long Reef.

Current Conditions

The current rainfall, water level and ocean conditions for Manly Lagoon are summarised in the following plots:-

Historical Photo Gallery

Below are a number of historical photos of the Manly Lagoon area. Click on the thumbnail to view the image.

Manly foot bridge (circa 1915), site of the current Queenscliff road bridge Queenscliff Beach and the original Queenscliff Surf Life Saving Club (circa 1930) Flooding in Riverview Parade, Manly Vale on 21st November 1969 View of Manly Lagoon entrance from 9th floor apartment on 16th November 1969
View of Queenscliff Bridge and Manly Lagoon entrance on 16th November 1969 Flood waters on 4th May 1977 at corner Lakeside Cres and Pittwater Rd Nth Manly Manly Lagoon entrance on 31st August 1996 looking towards the ocean Manly Lagoon entrance looking toward Queenscliff Bridge on 31st August 1996

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