Scientists have documented an abnormal and dramatic surge in sea levels along the U.S. gulf and southeastern coastlines since about 2010, raising new questions about whether New Orleans, Miami, Houston and other coastal communities might be even more at risk from rising seas than once predicted. The acceleration, while relatively short-lived so far, could have far-reaching consequences in an area of the United States that has seen massive development as the wetlands, mangroves and shorelines that once protected it are shrinking. An already vulnerable landscape that is home to millions of people is growing more vulnerable, more quickly, potentially putting...