The Challenge

The Woongoolba floodplain is located to the east of the Pacific Motorway about halfway between Brisbane and the Gold Coast within the Council of the City of Gold Coast boundary. The floodplain is impacted by flooding from the local catchment that extends east from the Darlington Range as well as regional flooding from the Logan/Albert catchment. Traditional land use in the area is sugar cane farming. Originally conceived in the 1960’s the Woongoolba Flood Mitigation Scheme was aimed at ensuring that flood waters would be drained from the floodplain within four days.
With development occurring rapidly upstream of the scheme boundary, Council engaged WMS to determine the potential impacts to performance of the drainage scheme. Pressure to significantly change land use (from agriculture to residential) within the scheme boundary also exists. Additionally, opportunity exists to upgrade the scheme.

Approach and Outcomes

WMS liaised with representatives of the cane farming community in order to identify hot spots and to obtain flood spot heights to enable calibration. WMS also developed a 1D/2D numerically coupled MIKE FLOOD model using a 10 m grid and lateral coupling of 1D drains. During the model development process a near Highest Astronomical Tide and a small flood occurred. WMS was able to use these events to verify model performance. The model was then used to assess the performance of potential drainage upgrades.