About ten months ago, I was worrying about the Mosul Dam across the Tigris River in far off Iraq. It was constructed on Saddam Hussein's watch but also on a really dodgy foundation. At the moment 10 billion tonnes of water are behind the dam and at least 1 million people are downstream hoping everything will be okay.
just 3 years ago] - dang that climate change! The Oroville Dam is the US's tallest and is made of concrete-faced rubble. The lake behind is full to brimming and so water was let off down a concrete spillway. That GUSH of water - 35,000 cu.ft/sec = 1,000 tonnes/sec has eaten a huge hole in the spillway and the water has topped out the emergency spillway next door. The emergency spillway is just a concrete lip - never used in the 50 years since the dam was topped out 50 years ago - at the top of a rock-and-dirt hillside falling 230m to the Feather River below. If the water flow undercuts the emergency spillway lip then water will start to lower the hill top possibly catastrophically: a 10m lowering of the lake is conceivable and the lake is 6,000 hectares in extent; that's a lot of acre-feet of water. Water is coming into the reservoir at an estimated rate of 5,000 tonnes/sec. Weather is forecasting several more storms coming in this week.
Maurice McCabe but does cover Oroville on Page 5. I've clipped a pic from RTE to show the was-concrete spillway and the emergency spillway to the left. The dam itself is massively off-camera to the right. Millions of salmon fry in the spawning gravels downstream - they're screwed (sorry). You can pick up enough links to satisfy your further curiosity at Metafilter.
Let's us hope that we don't have a Vajont 1963 , or even an Eigiau 1925 over there.