The unprecedented rain event in Townsville caused the north Queensland city's Ross River Dam to reach more than 200 per cent capacity, prompting authorities to open the spillway gates to their full capacity. The release caused 1,900 cubic metres of water per second to flow downstream, inundating several Townsville suburbs. The Ross River Dam is a gated dam and was built in 1971 for flood control and water storage, with a catchment area of 760 square kilometres. The dam had a $115 million upgrade that was finished in 2007 to install three spillway gates to control the flow downstream and increase its capacity to 233,187 megalitres. On Monday afternoon the dam was at 229 per cent capacity and slowly falling, down from a peak of 244.8 per cent. The dam is owned and managed by the Townsville City Council with operational help from SunWater. How does a gated dam work? The full supply level of a dam, when it is at 100 per cent capacity, is the approved water storage level of the dam for drinking or irrigation purposes. Loading So when the level rises above that in a gated dam, then controlled releases are conducted for flood mitigation and the dam's structural safety. For un-gated dams, operators have no control over the water that flows over the spillway once the dam's water level surpasses the full supply level. University of Queensland's School of Civil Engineering Professor, Tom Baldock, said the elevation of the dam and the size of the reservoir could create more storage space. "The storage capacity is dependent on reservoir geometry, so it's usually given a storage volume and as the level of the dam goes up, the area of the reservoir is increasing rapidly," he said. "The side slopes [of a reservoir] tend to be quite flat so you don't have to increase the height of the water to get a much bigger volume resulting from the increased surface area of the reservoir. "That means you can go from 200 to 250 per cent capacity without a very large rise in the water level — it's a non-linear rise in the water level." Data from the Australian National Committee on Large Dams said the reservoir in the Ross River Dam could hold up to 803,565 megalitres of water in flood mitigation. The Ross River Dam Emergency Action plan stated the dam's full supply level is when the elevation level (height of the river) reached 38.55 metres and the gates are fully opened when the elevation level reaches 43 metres. Loading Will the dam fail? Bureau of Meteorology senior hydrologist, Chris Leahy, said a dam was not compromised when its capacity was more than 100 per cent. "The way it works with these dams is that 100 per cent is the force of flow level for the water supply requirements for the dam, and then anything above that is used for flood storage," he said. "Flood storage will only be held in there for a short period of time — there's certainly no risk to the structural integrity of the dam at those types of levels [when it's over 100 per cent], but you'll only keep the water in there for a short time before it's discharged out." The Ross River Dam underwent an upgrade that finished in 2007. ( Supplied: Meridian Helicopters The Ross River Dam's emergency action plan said it was currently at Alert Level STAND UP-3. However, if the height of the river (EL, elevation level) goes above 43.6 metres and the flow rate exceeds 2,100 cubic metres per second, that raised the alert level to STAND UP-4. The final alert level — STAND UP-5 — means dam failures are extremely likely. There is no rating that triggers dam failure. However, the emergency action plan states under Stand Up-4, that the vicinity of the dam must be evacuated if the river height reaches 47.5 metres. Is this a record flood? The height of the Ross River at Ross River Dam peaked at 42.99 metres on Sunday night at 10:00pm, the Bureau of Meteorology said. Floodwaters flow fast over Aplin's Weir in Mundingburra near Townsville on February 3. ( Facebook: Donna-marie Audas The current flooding smashed the previous record for the dam, which reached a height of 40.73m on March 21, 2012. It also smashed rainfall records, according to the Bureau of Meteorology 1,134 millimetres had fallen at Townsville Airport in the last 10 days to 9:00am Monday morning — breaking an 80-year record. Far north, Ingham had also broken its all-time 10-day rainfall record, with 1,197 millimetres recorded.<doc-sep>Townsville residents in multiple suburbs have been urged to get to higher ground before 8.30pm as the Ross River Dam spillway gates are expected to be opened to their fullest settings on Sunday night. If the gates are opened, 2000 cubic metres of water per second will rush out of the dam toward the city's suburbs in a major flash flood. Residents evacuating to higher ground in Hermit Park, Townsville, on Sunday. Credit:AAP A warning from Queensland Police and emergency services issued at about 4.30pm urged residents to move away from the river banks and get to higher ground. Residents in Rosslea, Hermit Park, Railway Estate, Townsville City, Oonoonba, Idalia, Cluden, West End, Rowes Bay, Garbutt, Aitkenvale, Cranbrook, Currajong, Mysterton, Pimlico, Mundingburra, Douglas, Annandale, Kirwan and Thuringowa Central and South Townsville are urged to leave home and find safer ground immediately.<doc-sep>Queensland: Flames rise above trees in Deepwater bushfire top stories direct to your inbox SUBSCRIBE Invalid email Sign up to receive our rundown of the day'sdirect to your inbox When you subscribe we will use the information you provide to send you these newsletters. Sometimes they'll include recommendations for other related newsletters or services we offer. Our Privacy Notice explains more about how we use your data, and your rights. You can unsubscribe at any time. Once-in-a-century floods have forced more than 1,000 people to flee their homes and resulted in crocodiles appearing in suburban streets around the Queensland city of Townsville. About 1,900 cubic metres of water was released on Sunday night by authorities as dam reservoirs swelled beyond capacity due to monsoon rains. More than 1.16 metres (3.8ft) of rain was dumped in Townsville over the last seven days, with a further 100mm expected on Monday, the Bureau of Meterology said. The army was called into the northeastern Queensland city to help evacuations after the water release caused “dangerous and high velocity flows” along the Ross River. Queensland state Premier Annastacia Palaszczuk told Australian Broadcasting Corp TV: “Once in a century event happening here. I have never seen the likes of this before.” Which homes are at risk as Ross River Dam floodgates are opened? Numerous Townsville suburbs were flooded after dam gates were opened on Sunday 8pm local time (10am GMT). Less than an hour after authorities took action, the Queensland Fire and Emergency Services wrote on Facebook: “The message advises that dam gates are now fully open and residents will experience a sudden rise of fast moving water from the Ross River. Townsville floods MAP: Current weather warnings for heavy rain in place across Queensland “The following areas will experience imminent flash flooding as a result of significant, sudden rises in the Ross River: Rosslea, Hermit Park, Railway Estate, South Townsville, Oonoonba, Idalia, West End, Rowes Bay, Garbutt, Townsville City, Cluden, Hyde Park, Aitkenvale, Currajong, Pimlico, Mysterton, Mundingburra, Douglas, Annandale, Kirwan and Thuringowa Queensland is a tropical area of Australia used to flooding and monsoon rains but the current situation is rare. Even after the dam’s release it was still at 229 percent capacity, holding 532,000 gigalitres of water or the rough equivalent of Sydney Harbour. More than 15,500 homes in Townsville are still without power, according to Erggon Energy as reported by 7 News Townsville. Townsville floods MAP: Areas at risk of heavy rain Evacuation centres have been set up across outside of the city where people flocked to in recent hours. Many people were unable to salvage anything before leaving and were only able to rescue their pets. 7 News Townsville reporter Amelia Adam tweeted: “Just interviewed a family at an evac centre. They said they went through Cyclone Yasi and bushfires in Canberra and they were a walk in the park compared to what they went through last night. Many people have been faced with some horrific things.” Townsville is a major port city for Australia in the north and the country's top exporter of copper, zinc, lead and sugar. Townsville floods MAP: An aerial view of the flooding<doc-sep>The floodgates of Townsville’s Ross River Dam have automatically opened, with residents of numerous suburbs in the firing line. Meanwhile, the city’s airport has closed. LATEST UPDATES THE Ross River Dam floodgates are fully open, with hundreds of thousands of megalitres spilling over. Townsville City Council and Queensland police are urging residents in the nearby suburbs to prepare for imminent flooding from a rapidly rising Ross River. Disaster plan reveals what happens if the Ross River Dam fails Up to 20,000 Townsville homes could go under water, police warn Townsville floods declared a catastrophe by Insurance Council Townsville floods: Townsville Mayor, Queensland Premier, emergency services and Bureau update community on disaster Suburbs to be affected include Rosslea, Hermit Park, Railway Estate, Townsville City, Oonoonba, Isalia, Cluden, West End, Rowes Bay, Garbutt, Aitkenvale, Cranbrook, Currajong, Musterton, Pimlico, Mundingburra, Douglas, Annandale, Kirwan and Thuringowa Central and South Townsville areas. The warning comes after the Bureau of Meteorology released a serious warning for the area warning of a “risk to life and property”. People in the affected suburbs above are being urged to reach higher ground and move away from riverbanks. The Ross River Dam spillway will release approximately 1900 cubic metres of water per second out of the dam, which as of 7pm was at 245.8 per cent capacity - a total of 573,059 megalitres. MAP OF POTENTIALLY AFFECTED PROPERTIES (PDF 900KB) The Bureau of Meteorology is warning of dangerous and high velocity flows in the Ross River from Sunday night into Monday, after Townsville was hit with record breaking rainfall. The seven-day total to 9am Sunday was 1012mm, beating the previous seven day record of 996mm in 1998. This rainfall also beats the 10 day record of 925mm in 1953, with the bureau predicting many other locations will have record breaking rainfall totals. The Ross River at Aplin Weir is currently at 3.11 metres and rising, with major flooding, and is forecast to reach around four-metres late Sunday evening with further rises possible. AIRPORT CLOSED Townsville Airport has closed, with all flights in and out cancelled. The airport released a statement via Twitter urging passengers to contact their airlines for further details regarding their flight options. The decision to keep the airport closed will be reassessed in the morning. The action has been taken as the city’s flood crisis worsens. Water is released from Ross River Dam. Picture: Zak Simmonds PALM IS. WATER WARNING Residents in the Palm Island Aboriginal Shire Council area are being urged to boil all drinking water until further notice. The emergency alert was issued after the current deluge impacted the water treatment plant. People in the area are being urged to spread the message and to tell family and friends, and to monitor the Palm Island Aboriginal Shire Council website for further updates. SCHOOLS TO REMAIN CLOSED All state schools in Townsville and surrounding areas will remain closed tomorrow due to significant flooding. Education Minister Grace Grace said the decision to close all state schools in the flood zone was made to ensure the safety and welfare of staff and students. 1As the weather event moves further south, the department will also monitor developing conditions in the areas from Bowen to Proserpine,” she said. “I strongly urge parents to continue checking the Department’s School Closures website for the most up-to-date information about the status of schools in affected areas over the coming days as the situation is subject to change. “The safety of all of our staff, our students and their families will always be our highest priority.” There are 42 state schools closed, 21 Catholic and Independent Schools closed and 119 Early Childhood Education and Care Services closed. The school closures website – a live website that is constantly updated – can be found here. Parents should check local weather conditions and road access, and place their safety — and that of their children — above all else. A spokesman for Premier Annastacia Palaszczuk confirmed the Government had cancelled plans to hold a community cabinet on the Sunshine Coast this week due to the flooding disaster unfolding in North Queensland. Flooding at Giru, southeast of Townsville. Photo: Les Moffitt MORE RAIN TO COME WILD weather and saturating rain in the state’s north is set to continue into Wednesday, with the possibility of tornadoes. Townsville’s rainfall totals are an all time record, even surpassing the “Night of Noah” event of 1998. The Bureau of Meteorology say seven day totals in Townsville have reached 1,012mm as of 9am this morning, smashing the previous record of 886mm. BOM state manager Bruce Gunn said wild weather will continue with severe weather warnings for almost all of the Gulf of Carpentaria coast including Torres Strait Island for abnormally high tides and another severe warning current for much of North Queensland. He said the affects of the monsoonal trough was still to come with damaging winds expected and potential for tornadoes. “The possibility of wind gusts also exist with the onshore flow and there is some chance of tornadoes forming in that onshore flow as the convergence lines feed into the monsoon … there’s enough favourable wind sheer to make that possible,” Mr Gunn said. Emergency alerts have been issued for Hyde Park, Aitkenvale, Kurrajong, Rosslea, Pimlico, Mysterton and Mundingburra. Residents are being advised that the heavy intense rainfall on top of elevated flood levels is likely to cause flash flooding. Authorities urge residents to move to higher ground immediately if they are concerned. Evacuation centres are open at Heatley Secondary College on Fulham Road, and Ignatius Park College on Ross River Road. An emergency alert for residents of Hughenden in the state’s northwest has been also been issued. Flood water from the Flinders River is expected to cause flooding on the north side of the river. PHOTOS: Monster monsoon continues to lash Townsville OVERNIGHT: Officials fear today is D-Day for Townsville, as extreme rainfall and a catastrophic flood disaster engulfs the 185,000-strong north Queensland city. Locals witnessed incredible scenes of flash-flooding and 500 evacuations in nine of the hardest-hit suburbs — where 20,000 homes could be impacted in a worst-case scenario.<doc-sep>
Townsville dam spillway gates open fully, with flood zone facing further inundation Updated The gates of Townsville's dam have opened to their full setting, with the city council warning several suburbs should prepare for imminent flooding from a rapidly rising Ross River. Key points: Townsville sets a new seven-day rainfall record as flood emergency continues The opening of the spillway releases about 1,900 cubic metres of water per second Flooding from the dam release could affect 21 suburbs The Ross River Dam is releasing approximately 2,000 cubic metres of water per second, but was at 247 per cent capacity at midnight. The Bureau of Meteorology has increased its overnight rainfall prediction to 450 millimetres over the dam catchment by the end of Monday. The council says dangerous and high-velocity flows will occur and residents in the suburbs of Rosslea, Hermit Park, Railway Estate, Townsville City, Oonoonba, Idalia, Cluden, West End, Rowes Bay, Garbutt, Aitkenvale, Cranbrook, Currajong, Mysterton, Pimlico, Mundingburra, Douglas, Annandale, Kirwan, Thuringowa Central and South Townsville areas should prepare for imminent flooding. The council says an evacuation centre at Ignatius Park College at Cranbrook is now at capacity. Other centres are still operating at Burdell, Heatley, Alligator Creek and Bluewater. Bureau of Meteorology hydrologist Andrew Preece said with the dam gates fully open, the threat to Townsville homes was unprecedented. "What that means is we'll see dangerous and high-velocity flows in Ross River, resulting in risk to life and property," he said. "We'll see unprecedented areas of flooding in Townsville, a number of access routes cut, over the next 24 hours or so." Townsville Mayor Jenny Hill said dam operators were unable to stop the spillway gates from opening automatically. "Sadly, we received a huge burst of rain at about 1.30 this afternoon for about three hours, that just tipped us over," she said. "We thought we'd been able to manage it, but the rainfall we had, there was nothing we could do." Police said they had received a number of calls from people asking to be evacuated in Idalia and neighbouring Oonoonba. 'Tough night' ahead Premier Annastacia Palaszczuk toured the area on Sunday, saying it was "just torrential rain up here". "There has never been rain like this and the dam is going to get all the catchments of further water coming in, so we need everyone to take care," she said. "We're not out of this yet — it's not just the next 24 hours — this is going to go on for many days to come. "But the concern tonight of course is when those gates open — those low-lying areas — so please everybody listen to the alerts. "This is going to be a tough night — torrential conditions, the rain is coming down, the wind is gusty, it's not a night to be out on the road at all, but we need people to be safe." SES North Queensland regional manager Daryl Camp said rescue services were ready to help anyone. "We have pre-positioned resources all around the city so that we can still respond — fire and rescue, swift-water and rural fire — all over Townsville, so it doesn't matter where you are, we can still offer a response." The Townsville Airport has been shut for safety reasons as the city experiences the unprecedented flood disaster. All flights in and out of the north Queensland city have been cancelled, with diversions for any flights due to land. Heavy rainfall and destructive winds predicted The Bureau of Meteorology (BOM) issued a severe weather warning at 7:37pm Sunday predicting heavy rainfall, destructive winds and significant flash flooding between Ingham and Bowen, potentially extending as far south as Mackay from Monday. BOM said the monsoon trough was expected to shift slowly south over the next day or two to extend from Bowen, west to Hughenden and into the Gulf Country. Further heavy rainfall has been predicted for already saturated catchments in the area for the week ahead. BOM forecaster Dean Narramore said at 11:30am Sunday, there had been some extraordinary rainfall numbers coming in for the Townsville area, with a number of locations receiving over a metre of rain over in the last seven days. "Particularly a number of locations to the west of Townsville where we've seen 1.4 to 1.6 metres of rain — for some locations this is approaching their yearly average in just a week," Mr Narramore said.