Storm surge is basically the wind blowing water toward the shore at a rate at which it overwhelms levees and seawalls designed to protect the shore. The size of the storm, barometric pressure and the direction the storm is coming from are factors in causing the sea to surge. With a storm surge of 28 feet, combined with a broken levee, the city of New Orleans was quickly underwater. The storm surge in the Naples-Fort Myers area was expected to be 10 to 12 feet. The other problem with a storm surge is that they are fast: A 10-foot storm surge at sea level can submerge the first floor of a building in a matter of minutes.

Source: Los Angeles Times September 10, 2017 22:25 UTC