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Monday, February 13, 2017

Oroville dam ~ fears of huge overflow - massive evacuation ... at California

Oroville Dam is an earthfill embankment dam on the Feather River east of the city of Oroville, California, in the United States. At 770 feet (230 m) high, it is the tallest dam in the U.S. and serves mainly for water supply, hydroelectricity generation and flood control. Built by the California Department of Water Resources (DWR), Oroville Dam is one of the key features of the California State Water Project (SWP), one of two major projects passed that set up California's statewide water system. Construction was initiated in 1961, and despite numerous difficulties encountered during its construction, including multiple floods and a major train wreck on the rail line used to transport materials to the dam site, the embankment was topped out in 1967 and the entire project was ready for use in 1968. Since its completion in 1968, the Oroville Dam has allocated the flow of the Feather River from the Sacramento-San Joaquin Delta into the State Water Project's California Aqueduct.. .. ..

Miles away in China, the Yellow River or Huáng Hé,  is the third-longest river in Asia, following the Yangtze River and Yenisei River, and the sixth-longest in the world at the estimated length of 5,464 km (3,395 mi).  The river basin was the birthplace of ancient Chinese civilization, and it was the most prosperous region in early Chinese history. However, because of frequent devastating floods and course changes produced by the continual elevation of the river bed (due in part to manmade erosion upstream), sometimes above the level of its surrounding farm fields, it also has the names China's Sorrow.

Back home in India, it is all about water – which has flamed the States to become warring factions and placed at Parliament and doorsteps of Apex Court.  In a land fuelled by perceived notions, a movie Dam 999 further fuelled the hysteria. Away from Cauvery river sharing  snowballed  another river issue, it  originates from the Sivagiri peaks (1800m MSL) of Sundaramala in Tamil Nadu; runs a  total length of about 244 Kms, flows northwards for 48 kms and at Thekkady joins the west-flowing Mullayar – it is the river Periyar on which the dam constructed is a bone of contention – the Mullaperiyar dam.  It is a masonry gravity dam on the Periyar River, located 881 m (2,890 ft) above mean sea level on the Cardamom Hills of the Western Ghats in Thekkady, Idukki District of Kerala.  It was constructed between 1887 and 1895 by the British Government to divert water eastwards to Madras Presidency area (the present-day Tamil Nadu).   After a few minor earthquakes in 1979 in regions surrounding the dam, security issues were raised over its security. Since then, both the Kerala and TN governments have been at loggerheads over the security issue.
 
Now on the subject matter of the post – the Oroville dam – there have been mass evacuations,  to prevent flooding as the reservoir behind America’s tallest dam reached capacity and its main spillway was severely damaged.    On Saturday, water levels rose so high that an emergency spillway was used for the first time. Officials initially believed the measure worked. But on Sunday afternoon, as more water from record storms flowed into Lake Oroville, officials detected a hole in the emergency spillway. That prompted the evacuation order.  Officials worry that a failure of the emergency spillway could cause huge amounts of water to flow into the Feather River, which runs through downtown Oroville, and other waterways. The result could be flooding and levee failures for miles south of the dam, depending on how much water is released.

Nearly 200,000 people remained under evacuation orders on Monday (13.2.2017) as California authorities desperately battle to stop a collapse at the nation's tallest dam that could unleash a 100 foot tsunami if it fails. Concerned officials warned that in the worst case scenario a complete structural breakdown at the emergency spillway of Oroville Dam would unleash a torrent of water that would engulf Oroville within an hour. The ensuing flood from the 770-foot dam would put the city of Oroville and several other low-lying communities along the Feather River under 100ft of water. And amid the frantic evacuations, it emerged overnight that federal and state officials and some of California's largest water agencies rejected concerns 12 years ago about the precarious state the dam - which was built between 1962 and 1968.

An aerial of the Oroville Dam reveals the dangerous flooding at the spillway that has left the area in imminent danger of a catastrophic flood !   A massive hole is causing major erosion around the Oroville Dam in California – the  hole formed Tuesday and has continued to grow since then. If Oroville Dam were to suffer a massive breach, water would get to the town of Oroville within an hour, according to GIS maps maintained by CalFire. Within two hours, the small town of Briggs would be affected. In three hours, Gridley would be hit. Water would reach Live Oak in five hours.. it  would take eight to 12 hours for the water to get to Marysville and Yuba City. If the dam completely failed, flood depths could reach more than 100 feet in Oroville and up to 10 feet in Yuba City.

The dangerous situation sparked the California National Guard to put out a notification to all 23,000 soldiers and airmen to be ready to deploy if needed. The last time an alert for the entire California National Guard was issued was the 1992 riots.  And early on Monday morning, relieved officials said that water had stopped pouring over the dam's emergency spillway after they essentially rose 50-feet over a few days. They announced that although not nearly out of the woods, the situation had improved. However, another storm is predicted to hit the area by Friday, putting more strain on the dam and potentially sparking a catastrophic failure.

There naturally was panic as residents queued up evacuation. What they couldn't fit in their trunk they piled as high as they could in their downstairs Yuba City apartment and joined the line of traffic attempting to leave the city where they had moved just three weeks ago. Panicked and angry residents sat in bumper-to-bumper traffic hours after the evacuation order was given. A Red Cross spokeswoman said more than 500 people were at an evacuation center in Chino, California. The shelter had run out of blankets and cots, and a semi-tractor trailer with 1,000 more cots was stuck in the gridlock of traffic fleeing the potential flooding, said Red Cross shelter manager Pam Deditch.

Acting Director Department of Water Resources Bill Croyle said officials will be able to assess the damage to the emergency spillway now that the lake levels have been lowered.  Croyle said the department will continue releasing as much as 100,000 cubic feet per second from the main spillway to try and reduce the dam's level by 50 feet ahead of storms forecast to reach the area Wednesday. After years of drought Northern California has endured several months of exceptionally wet weather. Oroville and other lakes are brimming and have begun releasing water to make room for more runoff.

With regards – S. Sampathkumar
13th Feb 2017

Inputs & photos on Oroville dam from MailOnline

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