As two dams collapsed and stormwaters tore through the streets of the Libyan city of Derna, carrying bodies and buildings with them, Ruba Hatem Yassine, her pregnant sister and several older relatives clambered up a neighbor’s ladder to the roof to flee the grasp of the rushing flood below.

From there, they scampered from rooftop to rooftop along their narrow street, Yassine, 24, recounted Wednesday, two days after her terrifying ordeal. Eventually they sought shelter in a small storage unit on one of the rooftops, and watched for hours as the water overwhelmed the city.

They could hear their neighbors — trapped in half-destroyed homes by rising water or under rubble — screaming, "Save us, save us,” Yassine said, speaking by phone from a friend’s home in the nearby town of Marj. Once the floodwaters had somewhat subsided, other survivors helped her family of nine come down from the roof to safety.