An extreme flood at Lake Illawarra would threaten more than 1400 homes and caravans and might cost the community upwards of $50 million, a study has revealed.Properties in the lakeside suburbs of Primbee, Windang, Albion Park Rail, Yallah, Oak Flats and Kanahooka would be among the worst hit if the flood-prone lake overflowed.The long-awaited draft Lake Illawarra Floodplain Risk Management Study and Plan, now on public display, makes a number of recommendations to reduce flood risks around the lake.Authorities in Wollongong and Shellharbour will consider new education programs and revamped planning guidelines, including minimum floor heights for new developments.Eleven high-risk properties have been earmarked for voluntary house raising. Early warning systems may also be expanded to send emails or text messages to all residents living in the flood zone.Other options, including modifications to Windang Bridge, were not recommended.Historically, foreshore flooding at the lake has caused property damage and even evacuations.While most lakeside properties escaped the worst of the devastating March floods, Lake Illawarra Authority chairman Doug Prosser said new housing developments around the lake increased the risk of future damage.An extreme flood event is the worst-case scenario considered in the study, which was prepared for the Lake Illawarra Authority and Wollongong and Shellharbour city councils.It also considers a one-in-100-year flood scenario, which would threaten more than 600 homes and caravans and cost the unprepared community more than $7 million.Most of the affected homes fall within the Wollongong local government boundaries.Wollongong City Council's acting infrastructure and works director John Shepherd said the study was especially important for Windang residents, who ran the risk of being cut off in a serious flood.The council already had a flood education program in place, he added. "When a floodplain study or plan is adopted by council, council provides a letterbox drop with relevant information to householders and flood kits on what to do during times of flooding."Submissions on the draft study and plan close on August 5.A public information session will be held from 5pm today at the Rail Community Centre at Albion Park Rail.