Close to 200,000 people have been ordered to evacuate from areas surrounding the Lake Oroville Dam in California amid fears of severe flooding.<br /><br /> The National Weather Service urged people living downstream of the tallest dam in the US to flee to higher ground on Sunday, after authorities said that a damaged auxiliary spillway was on the verge of collapse.<br /><br /> “Immediate evacuation from the low levels of Oroville and areas downstream is ordered,” the Butte County sheriff said in a statement posted on social media. “This in NOT A Drill. This in NOT A Drill. This in NOT A Drill.”<br /><br /> Weeks of heavy rain had left Lake Oroville – the second largest reservoir in California – nearly full, leaving rural communities along the Feather river in danger.<br /><br /> However, relief over the end of a devastating four-year drought in California was short-lived after authorities and engineers began carefully releasing water from the dam after noticing that a large patch of concrete had been eroded from the spillway.<br /><br /> Looks like a significant increase in the hole in the #oroville dam spillway overnight. pic.twitter.com/DOSbJKAS2g— Mick West (@MickWest) February 9, 2017<br /><br /> Helicopters were seen dropping rocks onto the spillway in an attempt to plug the hole in the concrete that threatens to cause a collapse.<br /><br /> “What we are working with is approximately a 30-foot (10 metre) wall of water coming out of the lake. Not the lake draining but a 30-foot wall of water. That is why we took the appropriate measures that we did and implemented the evacuation process,” California Fire Incident Commander Kevin Lawson told reporters.<br /><br /> Hundreds of cars could be seen along Highway 99 as residents tried to make their way South or West to safety.<br /><br /> Evacuated Oroville is a ghost town https://t.co/ctCqo25zNv pic.twitter.com/ovBTePFkbT— Los Angeles Times (@latimes) February 13, 2017<br /><br /> When the reservoir reaches capacity, up to 150,000 cubic feet (4,250 cubic metres) of water can be released down the spillway.<br /><br /> Unfortunately, due to erosion, damage to the concrete path for the water run-off put releases on hold.<br /><br /> If lake elevation tops 900 feet (275 metres), water can be released down the emergency spillway on the adjacent hillside. <br /><br /> The fear is that water pressure from the large amount of rainfall could cause a further breach.<br /><br /> Graphics #OrovilleDam #Oroville how water is flowing down emergency spillway. Fear is water pressure may force larger breach nbcbayarea pic.twitter.com/YKEJP5qeol— Jeff Ranieri (JeffRanieri) February 13, 2017<br /><br /> Built between 1962 and 1968, the Oroville Dam lies about 150 miles (241 km) northeast of San Francisco.<br /><br /> It stands at 230m high, besting the famous Hoover Dam by over 12m.<br />
