DERNA, Libya — Locals now call Wadi Derna “the dam of death.”In a moment’s notice, the structure unleashed tens of millions of cubic meters of floodwater on Derna’s residents. The torrents swept generational homes and entire families into the Mediterranean sea — leaving onlooking survivors in a state of shock and horror. A road that connected the valley is now shredded — the two sides of asphalt reaching over the edge to each other. “We will never forget what happened here,” says Safwat Ashraf, a 24-year-old teacher. Safwat says he heard women and children screaming who had sought shelter in the school.