FLOOD WARNING SYSTEM
for the
MAROOCHY & MOOLOOLAH RIVERS

Maroochy River at Picnic Point (Maroochydore)

Contained in this document is information about: (Last updated November 2017) Flood Risk Previous Flooding Flood Forecasting Local Information Maroochy ALERT System Flood Warnings and Bulletins Interpreting Flood Warnings and River Height Bulletins Flood Classifications Other Links

Flood Risk

The Maroochy River basin has a catchment area of 630 square kilometres and is located about 100 kilometres north of Brisbane on Queensland's Sunshine Coast. The catchment lies on the eastern side of the Blackall Ranges and is bounded in the south by the Buderim Mountain divide between the Maroochy and Mooloolah Rivers, and in the north by a lowland divide between the Maroochy and Noosa River flood plains.

The Mooloolah River system drains a relatively small catchment with an area of 196 square kilometres that extends 25 kilometres inland from the coast. It flows east-northeast from the Blackall Range, discharging to the sea between Mooloolaba and Point Cartwright.

The Maroochy and Mooloolah River systems are susceptible to episodes of rapid flooding which can cause considerable damage to public and private property throughout the catchment. Continuing increases in population have accentuated the potential flood risk to life and property, and this trend is unlikely to abate given the current growth in the area.

Previous Flooding

Records dating back to 1893 indicate that major flooding has occurred fairly often in the Maroochy River. Significant flood events were reported in 1893, 1951, 1974 as well as in February 1992. During the latter event, flash flooding occurred in the smaller streams early on Friday 21st February, particularly in the area upstream of the Bruce Highway. At that stage, the main impact was the closure of several low level roads. By late Saturday 22nd, flooding in the lower reaches of the system caused inundation of about 225 homes to depths of up to 80 centimetres. The worst affected area was Pacific Paradise, adjacent to the mouth of the Maroochy River.

Records dating back to 1972 indicate that major flooding has not occurred frequently in the Mooloolah River, however flooding has occured periodically over the past 30 to 40 years. Significant flood events were reported in 1972, 1989, 1992 as well as in January 2011.

Flood Forecasting

In conjunction with the Sunshine Coast Regional Council Council, the Bureau of Meteorology operates a flood warning system for the Mooloolah and Maroochy Rivers based on the network of rainfall and river height stations shown on the map. The establishment of a real time ALERT flood reporting network has significantly upgraded the flood warning service that was in operation during the February 1992 event.

The Bureau's Flood Warning Centre issues Flood Warnings and River Height Bulletins for the Maroochy River catchment during flood events. River height predictions are given when moderate flood levels are likely to be exceeded at Dunethin Rock or Picnic Point.

Local Information

The Sunshine Coast Regional Council is able to provide further information on flooding in your area of the Mooloolah and Maroochy River catchment.

Maroochy ALERT System

The Maroochy River ALERT flood warning system was completed in the 1994 as a co-operative project between the Bureau of Meteorology and the then Maroochy Shire Council. The system comprises a network of rainfall and river height field stations located in the Sunshine Coast hinterland which report via VHF radio to a base station computer located in the Council office at Nambour. The field stations send reports for every 1 millimetre of rainfall and every 50 millimetre change in river height. 

In consultation with the Sunshine Coast Regional Council, the Bureau issues Flood Warnings for the Maroochy River. 

The base station computers located in the Sunshine Coast Regional Council office collects the data and has software that displays it in graphical and tabular form. The data is also received by the Bureau's Flood Warning Centre where it is used in hydrologic models to produce river height predictions. 

Flood Warnings and Bulletins

Interpreting Flood Warnings and River Height Bulletins

Flood Warnings and River Height Bulletins contain observed river heights for a selection of the river height monitoring locations. The time at which the river reading has been taken is given together with its tendency (e.g. rising, falling, steady or at its peak). The Flood Warnings may also contain predictions in the form of minor, moderate or major flooding for a period in the future. River Height Bulletins also give the height above or below the road bridge or causeway for each river station located near a road crossing. 

One of the simplest ways of understanding what the actual or predicted river height means is to compare the height given in the Warning or Bulletin with the height of previous floods at that location. 

The table below summarises the flood history of the Maroochy River catchment - it contains the flood gauge heights of the more significant floods.

Historical flood heights for all river stations in the Maroochy River Floodwarning network, as shown on the map, are available from the Bureau of Meteorology upon request.

Flood Classifications

At each flood warning river height station, the severity of flooding is described as minor, moderate or major according to the effects caused in the local area or in nearby downstream areas. Terms used in Flood Warnings are based on the following definitions.

Minor Flooding : Causes inconvenience. Low-lying areas next to watercourses are inundated. Minor roads may be closed and low-level bridges submerged. In urban areas inundation may affect some backyards and buildings below the floor level as well as bicycle and pedestrian paths. In rural areas removal of stock and equipment may be required. Moderate Flooding : In addition to the above, the area of inundation is more substantial. Main traffic routes may be affected. Some buildings may be affected above the floor level. Evacuation of flood affected areas may be required. In rural areas removal of stock is required. Major Flooding : In addition to the above, extensive rural areas and/or urban areas are inundated. Many buildings may be affected above the floor level. Properties and towns are likely to be isolated and major rail and traffic routes closed. Evacuation of flood affected areas may be required. Utility services may be impacted.

Each river height station has a pre-determined flood classification which details heights on gauges at which minor, moderate and major flooding commences. Other flood heights may also be defined which indicate at what height the local road crossing or town becomes affected by floodwaters. 

The table below shows the flood classifications for selected river height stations in the Maroochy River catchment.   

All heights are in metres on flood gauges. (B) = Bridge  (R) = Road

The above details are correct at the time of preparing this document. Up-to-date flood classifications and other details for all flood warning stations in the network are at: