In Australia, more than 30,000 residents of Sydney and its surrounds were told to evacuate or prepare to abandon their homes today as the country's largest city faces its fourth, and possibly worst, a round of flooding in less than a year and a half. Days of torrential rain caused dams to overflow and waterways to break their banks, bringing a new flood emergency to parts of the city of five million people.  <br />''<br />''Australia's Bureau of Meteorology manager Jane Golding said some areas between Newcastle, north of Sydney, and Wollongong, south of Sydney had received more than a meter of rain in the previous 24 hours. Some has received more than 1.5 meters.