- Flooding from the damaged Kakhovka dam has pushed Russia's lines back up to six miles, the ISW said.
- The think tank said flooding destroyed Russian positions and forced it to withdraw in some areas.
The flooding from a Ukrainian dam destroyed last week has pushed back Russia's lines in the area by as much as six miles, according to experts.
Washington DC-based Institute for the Study of War said in an update on Monday that "flooding has deprived Russian forces of previously held positions in at least 12 settlements on the east (left) bank of the Dnipro River and has pushed Russian lines back as far as 10 kilometers in some areas."
The east side of the Dnipro river is controlled by Russia, which has been accused of blowing up the dam.
The Kakhovka dam, which is upstream from the southeastern city of Kherson, was damaged on June 6, releasing a devastating flood of water downstream.
Ukraine said more than 40,000 people were affected by the flooding, and that as of Tuesday at least 10 people had been killed, with 41 more missing.
Ukraine accused Russia of blowing up the dam, while Russia has blamed Ukraine for the damage.
Last week the ISW also pointed to the impact of the dam's destruction on Russia's defensive positions.
"The flooding has destroyed many Russian first line field fortifications that the Russian military intended to use to defend against Ukrainian attacks," it said.
It added that "rapid flooding has likely forced Russian personnel and military equipment" to withdraw from key locations, pointing to the Oleshky and Hola Prystan settlements on the east bank where, it said, Russia had been firing artillery at Ukrainian forces.
"The flood also destroyed Russian minefields along the coast, with footage showing mines exploding in the flood water," it added.
Multiple Ukrainian officials said that considerable flood waters had flowed into communities on the Russian-occupied side of the river.
Ukrainian President Volodymyr Zelenskyy said last week that Russian forces were shooting at Ukrainian rescuers working in the area.
Ukrainian officials have accused Russia of blowing up the dam to hinder Ukraine's counteroffensive, which has just begun, something Russia refutes.
Ukraine's deputy defense minister, Hanna Maliar, said on Sunday that Russia blew up the dam to prevent a counteroffensive in the south, and that Russia was moving most of its combat-ready units away from the Kherson area.
But Russia accuses Ukraine of destroying the dam by shelling it.
Zelenskyy said the dam was too strong to be broken by artillery alone.
Ukraine's security service said last week that it intercepted call in which Russians admitted to blowing up the dam, saying it was destroyed in an attempt to blackmail Ukraine, which went wrong.
Three unnamed officials told NBC News last week that the US government has intelligence suggesting Russia is responsible.
Western countries have condemned Russia in broad terms, but without explicitly saying that Russia deliberately targeted the dam.