Her village, Stanislav, was under Russian occupation until last fall. It has been bombarded repeatedly by Russian forces since they were forced to retreat when Ukrainian troops recaptured territory in the Kherson region.

Evidence of the fighting is all around her. Burned-out tanks and armored vehicles line the road on the way to her home. Just outside the village, the tail of an unexploded S-300 Russian missile rises out of an emerald-green lagoon. Another missile is embedded in a field of red poppies and wildflowers.

But it was not an explosion that awoke Ms. Kamenetska on Wednesday. It was her husband, who pointed out the window at what he thought was a house floating past. By Wednesday afternoon, a dozen houses dislodged by flooding upstream could be seen from the shores of southern Kherson, like bobbing buoys across the delta.

The Ukrainian military warned residents along the coast about the “rapid flow of debris, fragments of various objects, boats, even building structures” being carried by floodwaters, adding that land mines may have been moved in the deluge.

Before the war, she said, the river brought communities together as a common source of food and recreation. Now, it is a front line that divides Ukrainian friends and families — the west bank held by Ukraine and the east bank held by Russian forces.

“For me, it’s despair that we can’t help people who have been waiting there,” Ms. Kamenetska said, referring to those stranded by floodwaters on the Russian-controlled side. “They were waiting for liberation but now they’re suffering.”

Mykola Shuliuk, 68, lives a few miles away from Stanislav in the coastal village of Lupareve, in the neighboring Mykolaiv region. Though his village was never occupied by Russia, it was on the front line for months, when he spent long stretches hiding in basement bunkers.

Mr. Shuliuk, who helped clean up the fallout at the site of the Chernobyl nuclear disaster in the 1980s, said that the effects of the dam disaster would only worsen.

“I just saw cars, horses, cows were floating,” he said. “It’s a horror.”

He wore old army fatigues, a hat celebrating the sinking of the Russian warship Moskva early in the war, and sneakers with the colors of the Ukrainian flag on the sides.

“This is a catastrophe not only for us but for the whole world,” he said. “It’s about flora, fauna, animals, fish, everything.”

Echoing statements from Ukraine’s leaders, he said he had no doubt that Moscow was responsible for the destruction of the dam, which is under Russian control. Russia has offered contradictory accounts about what happened at the dam, blaming Ukraine for the disaster without offering evidence.

Andriy, a Ukrainian soldier engaged in active service who gave only his first name, said he had been unable to reach his father, who is living under Russian occupation in Nova Kakhovka, a city adjacent to the dam.

“It’s terrible,” he said. “I can’t even watch the videos. The House of Culture, the zoo, the river bank where the college graduates used to celebrate the last day of studies around this time of the year — all are under the water.”

Evelina Riabenko and Anna Lukinova contributed reporting.