Disaster plan reveals what happens if the Ross River Dam fails
A DISASTER plan has revealed what would happen if the Ross River Dam was unable to control the release of water or it failed.
Townsville
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A DISASTER plan has revealed what would happen if the Ross River Dam was unable to control the release of water or it failed.
The vast majority of the city would be inundated if the Ross River Dam failed, but that’s been characterised as an “extremely rare event”.
If the city was flooded, residents in inner-city areas including Belgian Gardens, North Ward, Townsville City, South Townsville, Railway Estate, Hermit Park, and Hyde Park would be directed towards the high ground of Castle Hill.
People in Stuart, Cluden, Oonoonba, Idalia, Rosslea, Mysterton, Pimlico, Cuarrajong, Garbutt, Mount St John, Bohle and the northern beaches would be directed south towards the “high ground line” of the Bruce Highway.
Flooding could potentially be caused by a “flood release from a dam” which occurs when catchment inflows raise the storage level above the “Full Supply Level” of 38.55m, resulting in a discharge from the spillway of the dam.
As of 6am February 2, 2019 the Ross River Dam was at 193% capacity, with a volume of 449,879ML.
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Townsville City Council documents state the Ross River Dam had been designed to conform to modern design standards, so that its failure is “highly unlikely”.
The plan also deals with the event of a terrorist attack on the dam and a meteorite strike.
In the event the Ross River flooded or the dam failed, the council would send a text and voice message to residents warning of flooding.
>> Before and after: Stunning photos of Ross River Dam
Black zone
An area known as the “black zone” would be first impacted by flows of the Ross River.
The Black Zone depicts areas with flood emergency issues for flows of 570 m3/s from Ross River dam – dam water level of 41.1m AHD under standard operating conditions.
Areas within the Black Zone include parts of Rosslea and parts of Railway Estate which may also be impacted when tidal levels are elevated.
With standard operating conditions for the dam gates, the probability of this event is 5 per cent in any given year. It should be noted that rainfall downstream of Ross River Dam will also influence flooding, potentially beyond the zone depicted.
Brown zone
The Brown Zone represents the areas of Townsville impacted by flows at the upper limit of the gate operations for Ross River Dam. The Brown Zone depicts areas with flood emergency issues for flows of 960 m3/s from Ross River Dam – dam water level of 42.5m AHD under standard operating conditions. As dam water levels rise above this level, the gates will fully open as part of the standard operating conditions required by the dam safety regulator. Areas within the Brown Zone include parts Rosslea, Railway Estate, Oonoonba and Idalia.
Pink zone
The Pink Zone represents the areas of Townsville impacted by large flows from Ross River Dam once the gates are no longer able to control the releases downstream.
The Pink Zone depicts areas with flood emergency issues for flows of 2,100 m3/s from Ross River Dam – dam water level of 43.8m AHD under standard operating conditions. Areas within the Pink Zone include parts of Rosslea, Railway Estate, Oonoonba, Idalia, Hermit Park, Hyde Park, Pimlico, Currajong, West End, Mundingburra, Aitkenvale, Annandale, Douglas, Kirwan, and South Townsville. With standard operating conditions for the dam gates, the probability of this event is 0.05 per cent in any given year.
Green zone
The Green Zone represents the areas impacted by flows in the event of a failure of Ross River Dam. The Green Zone depicts areas with flood emergency issues for a collapse of the dam embankment followed by a massive outflow from the dam. Much of the urban area of Townsville around and to the east of the Bohle River is within the Green Zone, other than higher ground around Mount Louisa, Castle Hill and Mount Stuart (Annandale/Douglas). The probability of the dam failure is difficult to quantify, however it would be an extremely rare event, with a probability far lower than that for the Pink Zone event
The Ross River Dam was this morning at 87 per cent and rising. There was no indication of a flooding disaster in the immediate future.
The dam is at its highest level since 2013 when it peaked at more than 100 per cent.
Check out the evacuation plan here and the Emergency Action Plan—Ross River Dam here.
Originally published as Disaster plan reveals what happens if the Ross River Dam fails
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