- Thousands of Sydney residents have been warned to leave their homes as heavy rain and thunderstorms threatened to overwhelm Manly Dam on Tuesday.
- A dam in Sydney’s north was given a “get out immediately” evacuation order for 800 houses in the low-lying districts below, after a red level warning was issued. Amber-level warnings were sent to surrounding households about an hour later, when water levels had dropped.
- SES Commissioner Carlene York noted, “The rain and thunderstorms have not yet stopped.” If [the dam] passes over that region today, we may have to revert to the evacuation order that was issued before.
- Since 9 a.m., the Bureau of Meteorology has recorded between 50 and 100 millimetres of rain in the northern suburbs, moving toward the Central Coast (BOM).
- Those who live or work near Narrabeen Lagoon have also been issued with a flood warning, with people urged to leave through Pittwater Road by 7pm.
- This is all you need to know about Sydney’s dam system and what you can do to be prepared as heavy rains continue throughout the city.
What happened at Manly?
- Although Sydney’s water comes mostly from Warragamba Dam, Manly Dam and its surrounding bushland are increasingly utilised for recreational activities like as swimming and water skiing.
- It was established in 1892 to provide water to Manly and the surrounding region and has since been extended many times to meet the increasing demand. Its usage as a water supply was gradually phased out by 1929 owing to the fast population increase.
- Dam construction in the 19th century has recently been recognised as a cultural asset.
- It began to fill up on Tuesday, when it was battered by thunderstorms and heavy rain. An evacuation order was issued when the NSW SES got word that the dam’s level had risen to red. “The data was not really nearly as high as expected,” SES spokesman Greg Nash tells the New York Times.
- The current amber status indicates that the SES is still monitoring the dam’s water supply. “We will give an appropriate warning if it fulfils the conditions where it will overtop again,” Nash adds.
- Nash notes that “overtopping” refers to a circumstance in which the whole dam begins to spill over and there is a lot of flow downstream “when there is just too much water behind the dam.”
- On Tuesday, Commissioner York informed the Sydney Morning Herald that the dam’s wall was not at danger of collapsing.
