Ruba Hatem Yassine, her pregnant sister, and many elder relatives climbed a neighbor's ladder to the roof as two dams burst and storm floods ripped through the streets of the Libyan city of Derna, bringing corpses and structures with them.Ms. Yassine, 24, described how they escaped by scrambling from rooftop to rooftop along their tight street two days after their terrible incident. After hours of watching the water rise over the city, they decided to take refuge in a tiny storage container on one of the roofs.