Flood studies


Riverine and creek flooding is caused when the runoff from major storms exceeds the channel capacity of a river or creek and overflows onto the surrounding floodplain. With adequate rainfall monitoring and flood warning systems: riverine and creek flooding can be predicted in terms of extents and timing. It can generally be known in advance when and where a river or creek is likely to overflow its banks, so advance warnings and preparations can be made accordingly. The City of Mackay is built on the banks of the Pioneer River, as are the satellite townships of Finch Hatton, Mirani, Marian and Walkerston. Levee systems have been implemented to provide a level of flood protection from the Pioneer River in some locations.

Overland Flooding

Overland floods, or flash floods, occur when runoff from storms exceeds the capacity of the underground and overland drainage systems. When this occurs, water begins to flow over the surface of the land along natural flow paths or valleys towards the nearest creek or river. Overland flows usually occur with little or no warning following intense rainfall, often associated with short duration thunderstorm activity. They can be localised or widespread depending on the path or extent of storm activity.

Coastal inundation

Ocean tides can affect normal sea levels and cause flooding along the coastline and lower reaches of the Pioneer River and other creek systems, especially when combined with high rainfall. However, the tidal effects along an estuary or river diminish with distance inland. Storm surge is another mechanism that can affect water levels along coastal areas. Storm surge occurs through a combination of low barometric pressure, strong winds and large waves. It is generally uncommon for extreme rainfall events and extreme storm surges to occur simultaneously, albeit the 1918 event in Mackay is an example of this occurring.

In progress and future studies

It is not feasible for council to complete flood studies over the entire region at one time. Instead, council has an ongoing program of works to map coastal and flood hazards across the region. Flood studies, particularly in urban environments require details of the stormwater network. Collection of this data can be time consuming and is reliant on weather conditions. For this reason, the general process for completing flood studies is for data collection to occur during the financial year before the flood study commences.

The section below provides a summary of the flood studies that are currently being completed and future planned studies. It is important to note that the timing and order of future flood studies are subject to change.

Studies currently in progress

Council has prepared drainage studies for the North Mackay, West Mackay and Andergrove/Beaconsfield sub-catchments and is currently seeking submissions and comments from the public by November 23, 2020. To view the studies please visit council’s Connecting Mackay page. A form is provided at the bottom of the page to provide feedback.

Following consultation, council will respond to submissions outlining how the submitters’ comments have been addressed. The studies will then be taken to council for consideration. Following adoption, the studies will be used in council’s development planning, flood hazard and emergency management systems and be provided to the Insurance Council of Australia.

Planned flood studies

Council are working with the Department of Natural Resources, Mines and Energy to collect aerial Light Detection and Ranging (LiDAR) data over the LGA. This information will provide an update to the 2015 LiDAR dataset over the urban areas of the region and be used to provide ground surface information for future flood studies. Pending the availability of updated LiDAR information, Council plans to complete the following

  • 20/21: Detailed survey of stormwater infrastructure within the McCready’s Creek Catchment
  • 21/22: McCready’s Creek flood study incorporating parts of Blacks Beach and Rural View
  • 22/23: Glenella Flood Study