A Man’s Drone Captured Floodwater Draining Into A Spillway Following Heavy California Storms

When a man in California flew his drone over a nearby lake, he was astonished by what he saw. Looking through the drone’s camera, it seemed as though he was staring deep into a black hole. Then when he slowly descended for a closer look, he almost lost control.

David B. captured these astonishing images over Napa County’s largest lake, Lake Berryessa. The county is a sunny region best known for its amazing vineyards and beautiful views – not, however, for portals into other dimensions. And so, while piloting his drone 1,000 feet up in the air over the surface of the lake, David couldn’t have dreamed of capturing footage like this.

The water was rushing down a pitch-black hole that had opened in the middle of the lake’s surface. Indeed, it was swirling away like someone had pulled out a giant bath plug, and almost two million gallons of water were leaving the lake every minute. But where to?

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David lowered his drone closer and closer to the roaring mouth of the hole. Then, suddenly, his drone started to wobble and shake, dragged off course. Fortunately, then, he is an experienced pilot and knew exactly what he was doing.

“When I lowered the drone into the ‘Glory Hole,’ it became unstable and almost crashed into the side,” he explained. He therefore quickly guessed that the rush of draining water was creating a vacuum. This was making the drone unstable as he flew closer to it, though – so he struggled with the controls to correct the drone’s flight path. Finally, he was able to pull his drone up and out of a potentially disastrous collision course.

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If he had failed, David would have found what remained of his drone some 2,000 feet away in Putah Creek. Lake Berryessa isn’t, it’s worth noting, a natural lake at all. It’s the seventh largest man-made lake in California, having been filled in the 1950s following the completion of the Monticello Dam.

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Standing 304 feet tall, the Monticello Dam supplies water and electricity to almost 600,000 people across Sacramento Valley and San Francisco’s North Bay. The dam was named after the town it replaced, and when the waters run low in times of drought, the ruins of old Monticello are still visible in the depths of Lake Berryessa.

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The townsfolk of Monticello had cleared out in the 1950s as the floodwaters gradually inched their way towards the town. Meanwhile, some 300 graves are said to have been relocated as the floodwaters rose – though fortunately the terrifying hole that nearly swallowed David’s drone wasn’t the work of angry poltergeists.

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Lake Berryessa has a capacity of approximately 521 billion gallons of water, above which it will begin to overflow. At maximum capacity, the surface of the reservoir rises more than 440 feet above sea level. But if the dam reaches its limit, then the excess water has to go somewhere. If it didn’t, of course, the structure itself could be damaged and might even collapse.

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Ordinarily, the water level wouldn’t be a problem. After all, California is famous for its dry weather and frequent droughts, and the state only lifted its most recent set of water restrictions in April 2017. As a result, it had been more than a decade since Lake Berryessa was last in any danger of overflowing. Even in October 2016 the lake was barely half-full, with the water level sitting below 400 feet.

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Weather can be unpredictable, however. Unusually heavy rainfall hit California in January and February 2017, causing significant damage – and even toppling an ancient tree in Calaveras Big Trees State Park. It also filled Napa County’s water reservoirs to the point of bursting and put the Lake Berryessa “Glory Hole” into action.

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The oddly-named Glory Hole is a spillway that sits just a few yards from the concrete lip of the Monticello Dam, draining away excess water. Its unusual shape is the source of the bizarre visual effect that drew in David’s drone and would go on to attract hundreds of locals.

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This particular type of spillway is called a “morning glory” after the funnel-shaped flower. At its mouth, the hole is 72 feet wide and features a 200-foot vertical drop before narrowing into a 28-foot-wide pipe. Most of the time, the Glory Hole sits above the level of the water – and the freestanding pipe might even be mistaken for a very strange piece of modern art.

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It’s only when the water level rises to the 440-foot mark that the Glory Hole kicks into action, sucking away the extra water like a plug hole. In fact, “plug hole” – along with “bell mouth” – is another of the names typically given to this kind of spillway.

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At more than two million gallons per minute, the sheer amount of water spiraling down the funnel is staggering. That’s almost four Olympic swimming pools’ worth of water. As a result, the authorities are careful to block the spillway off with buoys and fences. A local website for Davis, California, also notes that “for obvious reasons, swimming near the Glory Hole is both prohibited and stupid.”

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In 1997, though, a local named Emily Schwalek spent 20 minutes desperately clinging to the concrete rim of the spillway. Sadly, she would ultimately lose both her grip and her life. That tragedy hasn’t stopped local skateboarders from using the Glory Hole’s horizontal exit in the dry months, however.

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The Lake Berryessa Glory Hole isn’t the only spillway of its type, either. Japan’s Nekogahara Pond has a morning glory spillway, as does Shing Mun Reservoir in China and the English Ladybower Reservoir. Covão dos Conchos in Portugal, meanwhile, features a spillway that might be mistaken for a natural formation and which creates a gorgeous effect when the dam overflows.

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Bizarre and beautiful though they may be, these systems are, moreover, vital to preventing disaster. Elsewhere in California, the Oroville Dam suffered a breach after the same heavy rains, and soon it became clear that the long-disused spillway had been damaged and could collapse.

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The situation meant that large areas had to be evacuated in case of a sudden tidal wave. In fact, some 200,000 people were forced to flee for their lives when it was discovered that a 30-foot-deep hole had opened up in the spillway. Fortunately, no collapse occurred, and the evacuated residents were soon able to return to their homes.

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Although spillways have long been considered a simple engineering necessity, new technology can reveal the true beauty of these structures. In fact, the sight at Lake Berryessa attracted numerous visitors keen to see the Glory Hole from the ground and the air. It’s hardly a surprise, though, as the spectacle is quite simply breathtaking.

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