Coastal Processes FAQ - What is the difference between storm tide and storm surge?

Storm Tide

Storm tide is the actual level of water in the sea and adjacent tidal waterways during a storm event. The storm tide level results from the additive combination of normal astronomical tide and the increase in water level due to the storm surge.

Storm Surge

Storm surge is the water that is pushed (actually pulled) towards the shore by the force of the winds associated with a coastal storm. Another minor component of storm surge is the inverted barometric factor resulting in a slight increase in water level due to the effects of the low pressure associated with both extra-tropical and tropical cyclones. The “pushing” (pulling) of water onto the coastline by the winds is the major component.

Storm surge and storm tide present the greatest potential for property damage and loss of life from hurricanes and tropical storms. Historically, nine out of ten hurricane fatalities are attributed to storm surge and extreme storm tide levels.

Storm Tide Facts

• Over 6,000 people were killed in the Galveston Hurricane of 1900 — most of these fatalities were attributed to the storm tide.
• Hurricane Camille in 1969 produced a 25-foot storm tide in Mississippi.
• Hurricane Hugo in 1989 generated a 20-foot storm tide in South Carolina.

Timing of Storm Occurrence and Tide Levels

When a coastal storm hits, the astronomical tide level can be at or between a high or low tide stage (water elevation). If a storm strikes during the lunar (or spring) tides, the water level may be higher than normal or lower than normal. The highest storm tide would result if maximum storm surge levels coincide with the time of the highest astronomical tide along a coastline.