the destruction of the Kakhovka dam feeds multiple hypotheses

It is a disaster of unprecedented magnitude. After the destruction of the Kakhovka dam, in territory occupied by Russian forces in Ukraine, the reservoir flowed into the bed of the Dnipro river, flooding entire territories. On Wednesday, June 7, more than 2,700 people had already been evacuated on both banks, according to the cumulative results of the Ukrainian authorities and the Russian forces. The eastern structure of the work and a large part of the infrastructure, including the hydroelectric plant, were washed away. The structure could deteriorate further, aggravating the situation.

>> Follow in our live the consequences of the destruction of the dam and the situation on the front of the war in Ukraine

Since Tuesday’s event, kyiv and Moscow have accused each other of destroying infrastructure on the Dnipro River. On Tuesday, the Ukrhydroenergo company claimed that an explosion had been triggered by the Russian occupants in the engine room, causing the structure to break. The Ukrainian army accused Moscow of having blown up the work to slow down its potential counter-offensive in the southern regions. On the Russian side, the occupation mayor of Nova Kakhovka, Vladimir Leontiev, first said that “everything was quiet” in the city, before reviewing his copy, half an hour later, and discussing “strikes”. Later in the morning, Kremlin spokesman Dmitry Peskov denounced an act “deliberate” of “sabotage”, “planned and carried out by order of kyiv”. By dismissing, therefore, the idea of ​​a strike.

Witnesses speak of “explosions”

It all started around 2:10 a.m. Monday night, when several users reported explosions on social media. Contacted by franceinfo, on condition of anonymity, a resident of Nova Kakhovka described “three to four explosions” of undetermined origin. Another writes to us that he has heard “several explosions of varying power”, which woke him up. A first around 2:15 a.m., then others, separated by an interval of “three or five minutes”. “Ten minutes of silence followed, before new explosions”, adds this man, who lives on the heights, and describes sounds “unusual”, which he is unable to identify. He specifies that these detonations were followed by the hubbub of running water, and that he was unaware, then, that the reservoir was destroyed.

What can these detonations correspond to? The Ukrhydroenergo company, through its manager Ilho Syrota, affirmed that the infrastructure was designed “to resist an atomic bomb”. Ammunition experts interviewed by the New York Times (in English) they also believe that a missile does not have sufficient power to break the dam. “The amount of exhibits a warhead can carry is limited.comments Nick Glumac, explosives specialist at the University of Illinois. Even a direct hit may not destroy the barrage.” According to him, only a gigantic explosion in a closed environment could have released enough energy to damage the structure.

“Russians and Ukrainians have excellent water engineers”, explains to franceinfo Bernard Tardieu, member of the Academy of Technologies and honorary president of the French Committee for Dams and Reservoirs. This dam, three kilometers long, is made up of a large riprap section (rocky materials), a factory, a lock and a concrete section with the gates. “It is very difficult to attack the dams because the arms of the valves are designed and used to resist horizontal thrusts”explains the engineer.

The hypothesis of explosives on the valves

Very robust, this part can still present weaknesses. “The easiest way is therefore to place loads on the arms of the valves”which ensure their rotation. “I am convinced that someone planted explosives”summarizes Bernard Tardieu, evoking “the destruction of several valves” in a very short time in Kakhovka. The engineer recalls the precedent of 1993, when Serbian forces trapped the Brana Peruca dam in Croatia. An English colonel then managed to lower the level of the reservoir, saving tens of thousands of people from a flood.

Russian forces were also installed in the area, therefore subject to flooding. The topology, moreover, particularly exposes the eastern bank downstream of the dam, and trenches dug by the Russian army were also submerged. A Ukrainian army officer, Captain Andriï Pidlisnyi, notably told CNN (in English) that his men had seen Russian soldiers fleeing and being carried away by the flood, after the collapse of the dam. He hypothesizes that the Russian general staff had not warned them, so as not to betray the element of surprise.

VSeome observers prefer to defend the idea of ​​a break in the structure, after months of carelessness and fighting. During the summer of 2022, a Ukrainian missile had already hit the pavement perched on the building. And on November 11, 2022, she was again hit by an explosion. This version of an accident, which differs from the Kremlin’s account, was defended by an anonymous specialist, quoted by the Russian news agency Tass, and by the leader of the occupation of the occupied territories of Zaporizhya, Vladimir Rogov. The Conflict Intelligence Team, a Russian group of independent experts, also writes (in Russian) that the dam did not resist, “under enormous water pressure reinforced by heavy rains last week”.

A dam in the heart of the war

Several journalists – including Evan Hill, of washington postor Christopher Miller, of New York Times – also pointed out that a section of roadway was missing the day before the flooding, although it was still in place on May 28. This would have fallen on June 2, according to satellite images released by the BBC (in English). The proof of a progressive disintegration of the dam? This argument does not convince the specialist Bernard Tardieu, who considers such damage insufficient to threaten the structure of the dam. “Blowing up any part of the bridge or causeway has no effect on restraintcomments the engineer. It just prevents you from crossing it.” Unless, perhaps, the successive explosions ended up damaging the valves of the reservoir.

VSome observers are also interested in the level of the Kakhovka dam reservoir, based on data from the Theia cluster, a project of ten French public institutions. This level suddenly decreased from the end of December 2022, before rising rapidly, from mid-February, and reaching an unprecedented level (17.55 meters). Such discrepancies are not surprising, according to Bernard Tardieu, because they are“a low reservoir, about 30 meters high, with large valves, which are probably more than 15 meters high”. As a result, the reservoir level “moves very quickly when maneuvers are performed”which explains the large tidal range (the difference between the peak and the bottom).

Nobody knows the intentions of the Russian occupier when it opened and closed the floodgates. The thrust of water on a dam does not depend on the volume of water stored, of course, but increases with the square of the height of water. But was a difference of one meter with normal (16.50 m until October 2022) enough to carry the blow? This gap is considered insufficient to cause the breakage of the structure, according to Bernard Tardieu’s analysis.

The international community remains cautious

To add to the confusion, a video emerged on Wednesday showing a small explosion above the already gutted dam. No certainty there either, but the Ukrainian authorities had already been accusing Russia for months of having undermined the dam. The International Committee of the Red Cross and the NGO Care, moreover, warned the populations of the region against a dispersion of these explosive devices, which riddle the sector and are carried downstream of the river.

While waiting to see more clearly, Western embassies continue to adopt a certain caution in their declarations, to the great displeasure of the Ukrainian authorities. Turkish President Recep Tayyip Erdogan on Wednesday suggested to the Ukrainian and Russian presidents the creation of an international commission of inquiry. Will Moscow want it? Seven days before the dam collapsed, Prime Minister Mikhail Michoustin signed a decree (in Russian) devoted to the hydraulic installations of the annexed territories. Article 10 provides that before 2028, no “technical survey” cannot be carried out “son accidents occurring as a result of hostilities, sabotage and terrorist acts”.