The flood plains of Sacramento are a geologic world away from the more cinematic California of coastal crags and lofty peaks. Yet that sometimes overlooked region could be home to one of California’s great disasters waiting to happen, according to a February report from First Street, a prominent climate risk prediction firm. The firm’s models suggest that the mounting risks of catastrophic flooding will drive Sacramento County — the heart of California’s fourth-largest metro area, at about 2.4 million people — to lose, in the average scenario, 28% of its population by 2055. … Few places in the U.S., if any, are more at risk of catastrophic flood than Sacramento. … In modern times, water has been corralled into aqueducts and dams and not allowed to pool into the fertile soil, drying out the wetlands and leaving hard, dusty earth that offers no buffer against floodwater.