Kakhovka Dam Destruction

Introduction

As we move into Summer 2023, meltwater and seasonal rains are filling the Dnipro River. The river serves as a natural regional border between the east and west of Ukraine, bifurcating the nation from the border with Belarus in the north until it empties into the Black Sea just east of Odessa in the south. The six dams along it serve as an important source of agricultural irrigation, flood control, and hydroelectric power. They also serve as vital lines of communication and movement for military forces, and the dams are vulnerable to damage by a defending or retreating force, with grave consequences. In southern Ukraine, the Dnipro serves as a front-line separating Ukrainian troops from the occupying Russian forces south of the recently recaptured city of Kherson and outlying areas.

This report aims to document some of the explosive threats that may come to bear on these pieces of vital infrastructure by analyzing the collapse of the Kakhovka dam and hydroelectric power station on 6 June 2023. While this report makes a formal assessment of the probable cause of the Kakhovka dam collapse, it should be noted that no party has claimed responsibility, and there is limited direct forensic evidence available. All conclusions therefore rely on assumptions of motive, intent, and access which may later be proved false.

Kakhovka Dam on 6 June

In the early hours of 6 June, residents reported explosions around the Nova Kakhovka Hydroelectric Power Plant dam which serves as a flood control gravity dam across the river, a hydroelectric power station, and a bridge for both rail and vehicle traffic. Seismic signals, detected by regional monitoring stations were deemed consistent with explosions by NORSAR (an international nuclear test ban monitoring organization.) Satellite images and reporting by multiple news organizations documented the collapse of the dam and the subsequent degradation of the structures supporting it as the reservoir behind the dam broke through and caused additional destruction.

In the composite image below created by Bomb Techs Without Borders from imagery published by Reuters; colorized image shows original dam, roadway and rail infrastructure.  Only the hydroelectric power station and part of the sluice gates remain; the road, rail line and most of the dam (blue outline) was destroyed, including the small ithsmus adjacent to the shipping locks (red outline.)

Assessment

This was not the first attack on this dam. In November 2022 there was an explosion with undocumented damage for which both Ukraine and Russia claimed the other responsible. CCTV video of the incident, obtained by BBC News shows a large surface explosion, consistent with a surface detonation or an exceptionally large subsurface device. Given the size of the fireball, dust cloud and the location (blue circle above) this could have been a large air delivered device (missile/bomb) or a surface placed charge. Damage at the time was not reported to have affected the bridge, dam, or power station. Video screen capture of the November 2022 explosion shown in the image below.

Kakhovka Dam (viewed from the southeast) – November 2022 attack location and CCTV of explosion in inset. Camera icon approximate location of CCTV. Source: AP News/BBC composite

Both countries have destroyed river crossings for tactical or strategic purposes since the beginning of the war. With neither country possessing a robust amphibious, riverine, or airborne lift capability these bridges and dams are vital to armies which move troops primarily via roads and highways.

Given that Russian forces controlled the dam, and the destruction appears to first have occurred at the junction of the sluice gate structure and the hydroelectric power plant; the most probable cause was purposeful demolition by retreating forces, with the purpose to slow Ukrainian advances across the Dnipro River. While an air attack cannot be ruled out, it seems improbable since it would be simpler to do it in person and would guarantee success of the operation. For many of the same reasons, we would rule out a subsurface attack. In addition, CNN reporting showed satellite images which confirm the road section at this junction was destroyed in the days leading up to the collapse. We assess that this indicates purposeful planning as it would be important to not just destroy the dam below the bridge but also the rail and road structure. Our conclusion is that the dam’s destruction was brought about by purposeful destruction of the roadway, followed by internal demolition of key structures which led to the further deterioration of the entire dam.

Military Dam Busting Operations

Because of their strategic importance to a country, dams have been military targets as long as they have existed. Destruction of a dam not only negates its value; but can also tie up important resources (concrete, oil, materials, people, equipment) used for its repair or reconstruction. The famous Operation Chastise of WW2 accomplished this with the successful, though costly, nighttime raid on the Möhne dam in Germany in May 1943. Conceived at a time where bombs had no guidance, bombsights were of dubious reliability, and where previous attacks using air dropped torpedoes had failed; the story is a success of ingenuity at a critical point in the war. But the losses were heavy, and there was no mistake of the intent of the attack. Even in its success, it is unlikely a modern belligerent would commit such a force to the destruction of a single dam. With modern precision munitions, such a large force commitment would not be necessary to score a critical direct hit and could be done from a much safer distance. Though there is no evidence used here, with the largest conventional munitions (such as the MOAB) or tactical nuclear weapons, a direct hit may not even be necessary.

A Note on Underwater Explosives

Water, incompressible and dense, is an excellent partner for use with explosives against both surface (ships) and subsurface (submarine/divers) targets. And while an explosive could be placed in the river to float downstream and detonate once against the wall of the dam, the structure of dams, which are by necessity thicker the deeper they are, makes them more resilient to attack than hollow items such as metal ships and submarines. Concrete is almost three times as dense as water, and any charge would have massive forces to overcome to breach the structure. Even early torpedo attacks on dams during WW2 that were direct strikes only inflicted minor damage.

Divers placing charges in a dam's environment would encounter a nearly impossible task, not only hazarding the mission but their own lives. This is why, should one want to dismantle a bridge, one would place explosives on the metal girders and not the concrete piers. This does not mean a dam is impervious, and structures such as the metal sluice gates, turbine intakes, bypass channels are all vulnerable, though attacking these structures from the water would have a low probability of success and not likely lead to the type of destruction seen in Kakhovka.

Much like an iceberg, dams have most of their structure hidden underneath the water and are incredibly large structures. They withstand earth-altering forces by holding back water in equilibrium with their own structure and utilize escape mechanisms for when those forces grow to threaten the dam's integrity. Bridge and structure demolition attempt to target critical points of failure, using the weight or balance of the structure to continue the disassembly. Direct hits or explosive placement are critical; just as it was in WW2 it is today. To analyze this, we will first look at dam structure.

Dams are some of the largest, most robust structures made by man, capable of withstanding trillions of tons of pressure through extreme variations in environment. Below are cross sections of the Kakhovka dam (spillway and power generation) along with photos of the area believed destroyed during construction.

Dam and spillway diagram - Cross-section of the Kakhovka Dam: 1 – spillway dam; 2 – anchor trench; 3 – metal sheet pile; 4 – wave breaker; 5 – riprap; 6 – notch tooth structure with a metal sheet pile / Photo credit: Hydropower and comprehensive use of water resources in the USSR

Power generation station - Cross-section of the Kakhovka Hydroelectric Power Station: 1 – foundation slab; 2 – metal sheet pile; 3 – bottom water outlet; 4 – reinforced concrete bridge / Photo credit: Hydropower and comprehensive use of water resources in the USSR

The Kakhovka Hydroelectric Power Station under construction

Because the spillway is mostly concrete dam structure and metal spillways, primary access for charge placement would be from above via the railway, or by boat if placing charges along the pilings and sluice gates. In the case of the power generation station, due to its robust size, most critical points (turbine casement, outflow tunnels) are difficult to access from the exterior. An attack on the sluice gates would expect to cause nuisance flooding, and not the catastrophic structural failure observed.

Based on previously mentioned reporting, the roadway was destroyed just days before the main failure (see image below from AP News.)  For a retreating force, wishing to deny the use of both the river crossing and the power station; severing the roadway and railway prior to setting off other demolition charges would make tactical sense as it prevents ingress into the station and would allow the force to gain sufficient standoff from what would be expected to be a catastrophic structural collapse.

Kakhovka Dam just prior to 6 June with roadway destroyed, sluice gates adjacent to power generation appear open or damaged due to large amount of water flow (Source: AP News) – Inset: roadway section prior to destruction (Source: Google Street View)

Conclusion

The Kakhovka dam served as both a critical piece of Ukrainian infrastructure and a vital river crossing. An enormous concrete, metal, and earthen structure, the dam would have been nearly impossible to destroy from the surface. The catastrophic damage at the site indicates a very large amount of high explosives would be required given the dam’s dimensions and construction. Given conditions at the site, it is highly unlikely that divers would have been able to emplace the necessary explosive charges to produce this result. It is likewise improbable that an airstrike could have delivered sufficient explosive ordnance to cause this damage. It is therefore most likely that the dam was deliberately destroyed from the inside with a large amount of emplaced explosives as part of a planned withdrawal.

Sources:

(1)   Kherson-Mykolaiv-Battle-Map, Institute for the Study of War with American Enterprise Institute's Critical Threats Project, https://www.criticalthreats.org/wp-content/uploads/Kherson-Mykolaiv-Battle-Map-Draft-June-142023.png

(2)   Satellite image of Kakhovka dam on 7 June, Reuters, https://ichef.bbci.co.uk/news/976/cpsprodpb/131AE/production/_130045287_dam_crop_rtr.jpg.webp

(3)   Ukraine war: The moment an explosion rocks dam near Kherson, 12 November 2022, BBC News, https://www.bbc.co.uk/news/world-europe-63607625

(4)   Here are the key theories on what caused Ukraine’s catastrophic dam collapse, CNN, https://www.cnn.com/2023/06/08/europe/nova-kakhovka-destruction-theories-intl/index.html

(5)   Cross-section of the Kakhovka Dam and Cross-section of the Kakhovka Hydroelectric Power Station, Defense Express, Ukrhydroenergo: Russian Occupation Forces Inflicted Maximum Damage to the Kakhovka Hydroelectric Power Station, https://en.defence-ua.com/news/ukrhydroenergo_russian_occupation_forces_inflicted_maximum_damage_to_the_kakhovka_hydroelectric_power_station-6939.html

(6)   Kakhovka Dam satellite image, AP News, https://apnews.com/article/ukraine-russia-dam-collapse-before-after-photos-b504eb2ce21e2c30cbcf902fbd718b71

(7)   Seismic signals recorded from an explosion at the Kakhovka Dam in Ukraine, NORSAR, https://www.jordskjelv.no/meldinger/seismic-signals-recorded-from-an-explosion-at-the-kakhovka-dam-in-ukraine  

(8)   The Incredible Story of the Dambusters Raid, Imperial War Museums, https://www.iwm.org.uk/history/the-incredible-story-of-the-dambusters-raid