The Causeway is 150 years old and features a horse-drawn tram service, one of the last of its kind in Australia.
The new design, released for consultation ahead of a detailed design phase, will have a different alignment to the existing structure.
The new alignment will keep the existing Causeway temporarily available for community use while the new build takes place.
The total project cost will be finalised in the design phase but the State Budget for 2019-20 committed an initial $20 million to the project.
Minister for Transport, Infrastructure and Local Government Stephan Knoll said the government has secured the future of the Causeway.
“The new and improved Granite Island Causeway, along with the Island itself, will continue to be an iconic tourism drawcard for the region,” he said.
“Earlier this year we finalised the Causeway’s temporary repairs so we could maintain access to Granite Island and now we’re getting on with the job of delivering a long-term solution.”
Member for Finniss David Basham said the Causeway had been an iconic piece of tourism infrastructure in South Australia for more than 150 years.
“The Victor Harbor Causeway is one of the biggest tourism drawcards in Victor Harbor and the broader Fleurieu Peninsula region,” said Mr Basham.
“Securing the future of the Granite Island Causeway goes a long way to securing the future of the tourism industry in the region which is so important to our local economy.”