Sydney residents were ordered to flee Wednesday as heavy rain swept down Australia’s east coast, burying towns in floodwater, killing 13 and putting hundreds of thousands at risk.
A week of torrential rain has swollen rivers and reservoirs to overflowing levels, spreading havoc across an 800-kilometer (500-mile) area.
More than 30 evacuation alerts have been issued from Brisbane to Sydney, and numerous dams are overflowing, with some near Sydney on the verge of bursting.
Residents have sought sanctuary on higher ground, in makeshift evacuation centres, or by clambering into attics or onto rooftops, praying for a boat or helicopter to come to their rescue.
The state’s record-breaking rain, which flooded the north before travelling south to Sydney, was described as a “one-in-1,000-year storm.” Sharon Cadwallader, the mayor of Ballina shire council, told that the town was expecting a one-in-500-year flood before it was flooded on Wednesday.
The report makes no mention of a once-in-a-1,000-year flood, but it does detail the estimated frequency of various flood peaks, as monitored by a gauge at the city’s rowing club.
The highest point is 16 metres above sea level, which corresponds to the “probable maximum flood” level for a hypothetical one-in-100,000-year flood. A one-in-500-year flood will be 13.4 metres high, a one-in-100-year flood will be 12.4 metres high, and a one-in-10-year flood will be 10.9 metres high.
