Storm Surge, Storm Tide, Hurricane Hazards

Storm surge is a phenomenon caused by the extremely low pressure and strong winds around the eye of a hurricane or typhoon that cause a dome of water to form at levels higher than the surrounding ocean surface. Large swells, high surf, and wind-driven waves ride atop this dome as it impacts land areas causing extensive damage to facilities and the shoreline environment. This buildup of water can produce severe flooding in coastal areas, particularly when storm surge coincides with normal high tides. Any land mass in the path of storm surge will be affected to a greater or lesser extent, depending upon a number of factors. The stronger the storm and the shallower the offshore waters, the higher the storm surge.

Storm surge is the most deadly of a hurricane's associated hazards. A powerful tropical cyclone is usually described in terms of its wind speeds, but coastal flooding causes many more deaths than high wind. Boats ripped from their moorings, utility poles, and other debris atop hurricane surge often demolish buildings not destroyed by hurricane-force winds. Even without the weight of debris, water is a powerfully destructive force. Storm surge can severely erode beaches and highways, and undermine bridges.

Section of coastline before and after Hurricane Hugo's storm surge hit Folly Beach, SC (Images: NOAA Magazine)

Storm surge, exacerbated by the effect of breaking waves, has the potential to destroy everything in its path. Along the immediate coast of a hurricane's landfall, storm surge is the greatest threat to life and property.

Storm Tide

A storm tide is the combination of storm surge and the normal astronomical tide. If storm surge arrives at the same time as a high tide, the water height will be even greater. For example, if a normal astronomical tide is 2 feet and a storm surge is 15 feet, then the resulting storm tide will be 17 feet in height.

As a hurricane nears land, the mound of water, topped by battering waves, moves ashore along an area of the coastline as much as 100 miles wide. The combination of storm surge, battering waves, and high winds can be life-threatening.

Hurricane