Welcome to Narrabeen 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 (MHL) and the Unisearch Water Research Laboratory for the Narrabeen Lagoon Joint Floodplain Management Committee for both Warringah Council and Pittwater Councils.

Lagoon Processes

Narrabeen 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 six hours in the future for three rainfall options. The model predicts water levels for three future environmental scenarios:-

Abating Conditions - Assumes no more rainfall and abating ocean conditions. Wave heights abate to one metre over the next 10 hours and surge levels drop to normal tides.
Persisting Conditions - Assumes average rainfall for the previous 3 hours will continue for another 3 hours then cease, and recorded ocean conditions persist for the next 10 hours.
Extreme Conditions - Assumes a 50 year annual recurrance interval rainfall for the next 3 hours and elevated ocean conditions with surges increasing at 25mm/h to a maximium of 0.6m and waves approaching 6m over the next 10 hours.

Model Results

Real Time Data Collection Network

MHL maintains a number of environmental recording stations in the Narrabeen Lagoon catchment area. Near real time data can be accessed by selecting the yellow station label on the following map or by viewing the data in the Current Conditions section below.

Catchment Rainfall

Seven pluviometers providing real time rainfall intensities are located at:

Avalon
Mona Vale
Cromer
Belrose
Middle Creek
North Manly
Narrabeen Creek

Water Level

There are six automatic water level recorders in the catchment. Two are in Narrabeen Lagoon and the others record infows from neighbouring areas. The stations are:

Narrabeen Bridge
Narrabeen Caravan Park
Middle Creek
Fern Creek
Mullet Creek
Narrabeen Creek

Narrabeen Lagoon Catchment Map

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 Narrabeen Lagoon are summarised in the following plots:-

Historical Photo Gallery

Following is a number of historical photos of the Narrabeen Lagoon catchment area. Click on the thumbnail to view the image.

Narrabeen Terminus Shops during March 1942 flood event Narrabeen shops again during March 1942 flood event Narrabeen shops again during March 1942 flood event

View of Narrabeen Lagoon entrance in November 1988 View of Narrabeen Lagoon from Collaroy Plateau Carpark near Pittwater Road Bridge during February 1990 flood event Robertson Street, Narrabeen during February 1990 flood event


Narrabeen Terminus Shops during March 1942 flood event	Narrabeen shops again during March 1942 flood event	Narrabeen shops again during March 1942 flood event


View of Narrabeen Lagoon entrance in November 1988	View of Narrabeen Lagoon from Collaroy Plateau	Carpark near Pittwater Road Bridge during February 1990 flood event	Robertson Street, Narrabeen during February 1990 flood event