KHERSON, Ukraine — Oleksiy Kolesnik waded ashore and stood, trembling, on dry land for the first time in hours, rescued after spending the predawn sitting on top of a cabinet in his flooded living room.
“The water came really quickly,” said Mr. Kolesnik, who was so weak he had to be helped out of a rubber boat by two rescue workers. “It happened so fast.”
Fetid, coffee-colored floodwaters, with plastic bags and bits of straw swirling around in the eddies, lapped at a street in Kherson, the regional capital, where rescuers staged a complete evacuation of a neighborhood cut off from the rest of the city by inundated streets.
Dogs in pet carriers barked. People spilled out of the rubber boats, exhausted, carrying at most a purse or a backpack and sometimes a cat or dog. The scene, overlooking a flooded square, was just one small snapshot of the vast disruption created by the destruction of the Kakhovka dam on the Dnipro River on Tuesday.
Kherson, a hub of Ukraine’s agriculture industry in the south, sprawls on bluffs on the western bank of the Dnipro River. Many neighborhoods were untouched by the flood. But low-lying areas by Wednesday were a panorama of water and floating debris. In one place, a refrigerator bobbed in the water.
Across the city and throughout southern Ukraine, officials rushed to solve a flurry of problems from the sweeping flood and the draining of the Kakhovka reservoir used for drinking water and irrigation — all along a front in the war.
On a late spring day, the rescue operation in Kherson unfolded without panic, but with an air of resignation at the vast task of pulling hundreds of people from their homes and finding them shelter elsewhere.
Rescuers ventured out in boats to pull stranded, frightened people from roofs or upper floors of homes. An occasional boom from artillery rang out.
Authorities were evacuating all residents of one neighborhood, called Ostriv, or Island, that had also been one of the city’s most dangerous areas for shelling.
In one spot, a red armchair floated in the flood. Elsewhere, trash bobbed in the filthy water.
“We were getting used to the shelling but I’ve never seen a situation like this,” said Larisa Kharchenko, a retired nurse who thought she might sit out the flood yesterday, when water was knee-deep in her yard but not yet in her home. By Wednesday, it was spilling through her door.
“Somebody needs to arrest Putin,” she said, referring to President Vladimir V. Putin of Russia.
In some areas of the Ostriv neighborhood, water reached the roofs of houses. “It just keeps coming,” said Ms. Kharchenko.
Alla Snegor, 55, a biology teacher, stepped out of a boat and looked back at the flooded city streets. She said she was trying to stay out of the water.
“Think of what is in this flood,” she said. “Pesticides, chemicals, oil, dead animals and fish, and also it washed away graveyards.” She said she had been boiling tap water before drinking it on Wednesday, in case the city’s waterworks had been infused with floodwater.
Serhiy Litovsky, 60, an electrician, said he was most worried about the long struggle ahead for southern Ukraine, one of the world’s richest agricultural zones but reliant on irrigation — most from the quickly draining reservoir.
“Without irrigation, it will be a desert here,” he said. “Without water, nobody will live here. The legacy of this will last dozens of years.”
The scale of the disruption was hard to fathom, he said. “Without war, this would be a major catastrophe. But this came along with the war.”