A survey of the USA’s vulnerability to hurricane-driven storm-surge damage found that more than four million homes worth over $700 billion are at risk along the Atlantic and Gulf Coasts. Storm surge — the massive mound of water that builds up and comes ashore as a hurricane moves over the ocean or Gulf of Mexico— is typically the most dangerous aspect of hurricanes. The report, released this morning by research and consulting firm CoreLogic of Santa Ana, Calif., found that Florida is the state most prone to storm-surge damage, with about 1.4 million homes at risk, worth a total value of $188 billion.