Sharon Smith has to plunge her toilet to get it to flush. On rainy days, wastewater spills into her yard from nearby drainage ditches. Twice in the last year her house has flooded, leaving behind the sickening smell of sewage, she said. Her carpets are ruined, the floorboards are buckling, the bathroom wall is pulling away from the tub, she said. In the laundry room, the worst-hit part of the house, the smell of mold lingers. “I want to move, because this flooding is ridiculous,” said Smith, 59. For decades, residents of Centreville, a nearly all-Black town of 5,000 in...