The survival of people in local camps and low-lying areas depended not on official evacuations but on whether they were paying attention, on their own, to weather alerts in the middle of the night.

Before the floods came, Camp Mystic’s sprawling 700-acre campground was dotted with green-roofed, cobblestone cabins and rows of cypress, live oak and pecan trees. After, bed sheets tangled in broken branches. Muddy clothes, an overturned canoe and other belongings from campers remained.