PEPINSTER, Belgium—Paul and Madeline Brasseur were at home with their two sons in the Belgian town of Pepinster when the water “came all of a sudden” late in the evening. It “was like a tsunami,” the way it entered the house and kept rising instead of retreating, said Paul Brasseur, 42. The family went upstairs and kept seeking safety during the night as the water climbed steadily below them. They ended up on the roof, watching. “We started to see buildings collapsing, people on the rooftops, buildings collapsing, falling into the water,” Brasseur said. Eventually, making their way from rooftop to rooftop, they ended up perched on one with 15 other people, waiting hours for help to come. A boat arrived to rescue the children, but it began taking on water while a makeshift jetty started to collapse. Brasseur held his sons back. “We held out, for those nine hours,” …