HOUSTON — A Holocaust survivor waded waist-deep in flood water. Dozens of people were trapped in a 14-story residence for seniors. A disabled man sat alone at home, without the aide who usually helps him, watching the water rise and unsure if anyone would come.

Harvey was terrifying for millions of people along the Gulf Coast. But it was particularly difficult for the region’s seniors and disabled, many of whom struggled to escape as the water rose. Now, some wait in shelters for chemotherapy, dialysis, pain medication, a pillow. Rescue teams are still evacuating people from their homes.

Inside her apartment in a Houston Housing Authority senior residence on Friday, Ida Szydlik insisted that she hadn’t been scared as the water rushed into her building over the weekend, filling the first floor. “We were just frightened for the other people,” said Ms. Szydlik, 97, as she began to cry. “I was in prayer, but I wasn’t scared, I was too busy praying that this would all go away.”

It is impossible to be sure how many older people have been affected by the storm, and many experts say it is too early to know how nursing homes are dealing with the impact.