HOUSTON — Dorothy Edmundson has always been the responsible one: the middle child who took care of her brother and sister, the dental office employee who rose from hygienist to manager, the watchful mother who whisked away the school cafeteria plate of corn served to her highly allergic daughter.

So the night of Aug. 26, as the outer rain bands of Hurricane Harvey reached their north Houston neighborhood, Ms. Edmundson, 34, and her husband, Ron, set their alarms every two hours to check their street for flooding, in hopes that their vigilance would give them an edge against the storm.

It did not.

“Get up, get up, water’s coming in,” she said, waking her two daughters early the next morning as the water rose inside their home.

Since that moment, when they stepped outside into the cold, waist-deep water and Ms. Edmundson heaved her daughters up to the highest spot she could find — the roof of her flooded black Chevrolet Suburban — their lives have been upended.