Huge task to defeat floods
DEVELOPERS will dig holes big enough to swallow half the Melbourne Cricket Ground to flood-proof a $1.2 billion residential estate planned on the Gold Coast floodplain.
The pits will become picturesque lakes but will not be completely filled with water to protect luxury apartments during an extreme flood event.
Planning documents lodged with the council show four lakes will be built on the 73hectare masterplanned community just south of the Titans’ home ground at Cbus Stadium, Robina.
Developer Breakwater said precincts would be constructed on “building platforms” raised above the Q100 Nerang River flood level to reduce the height of floodwaters on adjoining land.
“Platforms will be created by using approximately 800,000 cubic metres of earth,” a spokesman said. “This is based on a cut-fill balance within the site to create new lakes and channels.
“Breakwater’s new lakes will not be completely full of water, leaving additional flood storage capacity during the higher frequency but lower Q2, Q5 Q10 and Q50 flood events and some additional capacity during the Q100 event.
“This additional capacity will reduce the height of floodwaters on adjoining land.”
The MCG has an internal volume of 1.7 million cubic metres, and the 800,000 cubic metre dig for each platform to create the homes for 3700 residents illustrates the massive earthworks program.
“Floodwater will pass through the Breakwater site in new channels and will leave the site via existing bridges and culverts under the rail line,” the spokesman added.
“The channels will be incorporated into flood lands and landscaping and will only carry water during storm or flood events.”
The developer said similar approaches were used in Sage at Merrimac, Emerald Lakes and Robina Riverwalk.
The lake system will be connected to wetlands and a treatment plant is needed to maintain the quality of the stormwater discharged into it.
Ownership of the finished parklands and lakes would be given to the council so the areas could be used by the public.
“However, the responsibility for maintaining water quality to a high standard will stay with (the developer), and then the body corporates for each privately owned building.
“In the past, lakes have been dedicated to council creating a maintenance burden on the whole community, or have been kept in private ownership, creating gated communities where only the residents enjoy the lakes.
“Our approach ... will solve these two problems by opening the parkland and lakes to the public while not burdening council with the cost of maintaining lake water quality.”