Understanding Storm Surge and Why it is So Dangerous to Coastal Areas

As Francine bears down on the Gulf Coast, the topic of storm surge is being discussed with more frequency as well as a sense of urgency. What is storm surge and why is it so dangerous? Read on all for the details of one of Mother Nature's most powerful forces.

Storm Surge Responsible for Some of Worst Tropical Weather Damage

Many people focus on the potential impacts of rain and wind when discussing approaching tropical weather events. This is largely because wind speeds are used to determine the potential strength of a tropical weather event, including its specific storm category.

However, it is often the storm surge that leads to the most catastrophic consequences. Storm surge is defined as any rise in seawater along the coastal areas that is above normal. This type of surge is most typically caused by tropical storms and hurricanes.

The surge is caused as winds and high waves work together to cause water to pile up along the leading fringe of the forward motion. A hurricane in motion creates a large pile-up of water ahead of its track. Storm surge carries the potential of washing away buildings in its path. If strong enough, the surge can also permanently change the shape of a coastal area.

In addition to the power of the rapid push of water into areas not accustomed to seeing this surge, the strong winds coming on shore in front of the storm can cause their own damage. This damage then makes structures more vulnerable to the impacts of the incoming storm surge.

Factors Influencing Height of Storm Surge

The water accompanying a tropical weather event will rise to a specific height based on the natural slope of the coast. A more gradual slope translates to higher levels of storm surge.

The height that the surge reaches is also influenced by the shape of the coastal region. For instance, there are vast differences between straight coastlines and concave shapes. Concave coastlines featuring inlets or coves typically experience higher levels of storm surge due to the inherent funneling of the water that takes place when massive amounts of ocean water moves onshore. Conversely, a coastline that is straighter with a more abrupt slope tends to see lower levels of storm surge.

Additionally, the actual size of the incoming tropical storm or hurricane also impacts the amount of storm surge. Features that are larger in size generally create more water being churned up and sent up onto the coastal areas in its path.

Lastly, the winds whipping around within the center of circulation of the storm and the speed of the feature are also contributing factors that determine how much water will pile up prior to the landfall. All of these factors help forecasters to fine-tune their predictions about how much storm surge specific areas should expect to see with any given tropical weather event.

The highest wind speeds are often recorded within the right front quadrant of a storm in motion. This is the general area that is located to the right of the eye of the storm and also where the greatest amount of storm surge should be expected.

While forecasters also look at the predetermined coastal elements to make their predictions about storm surge, they also look at a number of other variables. These factors include the depth of the water at the point of impact, the expected tidal interactions, and the height of the waves generated by the tropical feature.

For example, tropical storms and hurricanes that make landfall at times of high tide will unleash storm surge well over what would be expected during times of low tide. This is why the timing of the storm matters so much.