ON THE MEKONG RIVER — When the Chinese came to the village of Lat Thahae, perched on a muddy bend of a Mekong River tributary, they scrawled a Chinese character on the walls of homes, schools and Buddhist temples. No one in this isolated hamlet in northern Laos could read what it said. But the...

MAPLE VALLEY, Wash. — Standing amid cottonwood trees and a thicket of other vegetation, Jon Hansen looks out over a sunlight-dappled ribbon of crystal water running over a rocky bed. He’s standing on a site that until recently was filled with houses and mobile homes — properties that flooded six times in 20 years when...