 It is the 2nd of December 1959 and a photographer is preparing their camera. Today they aren't documenting a wedding or a baptism but a disaster. The city of Rajesh has been battered by a wave of floodwater, the culprit, the dam that towered above it, the name Malpase. My name is John and welcome to Plainly Difficult. Background Our story starts and will ultimately end in the French Riviera and the need for a dam just north of the city of Rajesh in the early 1950s. Although a new project, the need for a dam in the region had been frequently brought up over several decades before. A number of previous projects had failed to get off the ground as early as 1865. You see the area had an issue with the Rayran River where it is mostly dry in the summer but conversely bursting at the banks in the autumn and winter. This is where a dam would be beneficial as it could attempt to regulate the flow of water and even out the Jekyll and Hyde like behaviour of the river. A dam would have a number of other benefits providing water for agriculture, domestic use as well as creating a lake for the use in the tourism sector. Before any concrete could be poured for the dam, geological surveys had to be undertaken. With each preceding project, surveys had been completed but these were not particularly useful as each proposed dam was a completely different design from the other. Well in preparation for the 1950s project, surveys at the valley at the potential building site took place in 1946 where a fault line was discovered by the science department in Marseille who were undertaking the initial site investigations. They advised that further investigation was required by excavating sections of the river banks to check their internal composition and identify any unweathered rock. They also suggested that other sites should probably also be considered. Another survey took place in November 1949 but a company in charge of the project decided to move the foundation site 200 metres downstream without any additional geological survey at a new placement. The dam was going to be an arch dam. These had a number of advantages, most notably cost as it uses a thin dam curved structure which spreads the weight of the reservoir into presumably solid banks. In comparison the 1800s design was going to be a gravity type which is very large and expensive so the new Malpassée dam was penned by renowned French civil engineer André Cohen and the project will be funded and owned by department Va. The dam was going to be 222 metres wide and was a doubly curved equal angle arch type with a variable radius. It was also to be made out of concrete with a masonry base. It was 6.78 metres wide at the base tapering up to a 1.5 metres thick at the top and 66 metres tall with an aimed reservoir capacity of 50 million cubic metres of water. On the right bank looking upstream a 10 metre high concrete abutment was also planned due to the topography of the valley. Level control was rather simple at Malpassée with a simple spillway at the centre of the dam which would allow water to well spill over the top. There was also a draw off made from a metal pipe of 1.5 metres in diameter cutting across the foot of the arch and shut by valves. If the level exceeded 99.5 metres then a fixed wheel gate would automatically open allowing water to flow down the draw off. This system was also able to be manually controlled. Construction began in April 1952 and after two years was complete in October 1954. Upon completion it was said to be the thinnest dam at its height in the world. But although the structure was complete the filling of the lake behind the dam would be a long long task taking several more years. Filling the reservoir at an even pace is vital. Over stress too quickly and structural failure is guaranteed but filling too slowly can cause issues well but we will come back to that later on in the video. This was the reason why Malpassée although built in 1954 wouldn't even be close to full capacity until 1959. As the water level increased cracks appeared and were discovered on the right hand side of the dam but were largely ignored. By mid-November 1959 the reservoir was roughly 7 metres below the crest and the cracks had turned into clear streams of water running down the right hand side of the dam. Somehow reservoir water was escaping. Now if things were looking a little bit ropey imagine what a torrential downpour would add to the mix. Well imagine no more. The disaster. So the Malpassée dam wasn't looking too great towards the end of November 1959. The dam's right side was still leaking and now a downpour of rain had arrived and wasn't helping. One of the dam's guardians Andre Ferro requested permission to open the gate for the draw off to reduce the reservoir level on the 2nd of December. Sensible idea. However this would have encroached upon construction of the Malpassée Nice motorway about 1km downstream from the dam. The reservoir would be allowed to fill up. Remember how it had taken years to fill? Well the water depth would increase by the rain by 4 metres in just 24 hours. Ferro was finally given the okay to open the gate at 6pm but by then was probably too little too late. Over 3 hours of the gate being open only a few centimetres of depth was removed. The dam was now groaning under the weight of the water. The dam breached at 13 minutes past 9 in the evening releasing a torrent of water 40 metres high at a speed of 70km. It destroyed everything in its wake including two small villages. The motorway finally reaching 20 minutes later, Régis, flooding the western half of the town. By the time it hit the town the wall of water was still 3 metres tall and littered with concrete debris. Eventually the torrent reached the Mediterranean Sea. Complete destruction had hit the region. All road and rail connections were severed, hindering residents from escaping and rescue workers from reaching the disaster site. 155 buildings were destroyed with a further 796 damaged. Cars were washed away and shops were decimated. An estimated 423 people lost their lives in a tragedy with many more injured. Hundreds were made homeless with 79 orphaned. Sadly dam failures caused incomprehensible tragedy to an area, but as the community began to clean up and try to heal the wounds, the cause had to be found. The aftermath Well, it would become quite clear that the interrupted and incomplete surveys of the dam site would come back to bite the project in the behind. When looking at the dam face upstream, you can see the likely start point of the failure, that right abutment, the one that was leaking. It was discovered after a thorough geological survey that there in fact was a fault line downstream from the dam. This stopped infiltration water from flowing away and instead collected below the foundations of the dam. As the weight and pressure built up from the filling of the reservoir, it unseated the dam's foundations. This formed cracks which were then filled by the impounded water in the reservoir, thus weakening the structure which led to the base being stripped from the valley. And when the right hand side failed, the rest would only have to follow. Pretty disastrous, but the issues with the dam were not just geological, but human. Although the dam was a good design, but placed incorrectly, people were the cause ultimately for the failure. You see the regulators saw the Malpase dam differently to others. Because it was mainly due to be used for agriculture, it attracted less scrutiny than that of a hydroelectric dam, and thus fewer inspections were undertaken. Little was done to check out the design due to the designer being so successful in his career, with over 70 structures under his belt, pretty much all of which were problem free. The long time it took to fill the reservoir was also an issue. As in 1959, the dam was still on its first filling, which really when testing out such a structure, it should be filled and emptied a number of times, building up to its final capacity. Instead, they just decided to reach full capacity in the middle of a downpour. They should have opened the gateway earlier to reduce the level in the reservoir. Building up of water behind the dam gradually by emptying and filling successive times gives time to find any issues and fix them as they arrive. Interestingly, over a number of court cases, the design of the dam was cleared, more putting blame on the choice of location. Andre Coyne, the dam's designer died a few months after the disaster, admitting full responsibility. But as we've seen, the real cause was not just down to one man, but a whole selection of issues. The dam was never replaced, but left as a reminder of the all too common issues of corner and cost cutting. So I'm going to rate this disaster as oboes people will hear about this and a six on my legacy scale. Do you agree? This is a plain different production. All videos on the channel are creative commons, attribution, share like licensed. Plain different videos are produced by me, John, in the currently very windy and wet corner of southern London, UK. I have Twitter and Instagram, so feel free to check them out if you want to see all the random photographs I post up. If you're enjoying this outro song, please feel free to go over to my second channel, my name is John, where you can watch the rest of the video and listen to the song in full. I'd like to thank my Patreons and YouTube members for your financial support, as well as the rest of you who tune in every week to see your dose of disaster. And all that's left to say is thank you for watching. I'm MrMusicMan, place out please.