According to the US Department of Commerce and the National Ocean Service, storm surge refers to an abnormal rise in the levels of seawater, caused solely by a storm.
This rise is measured as the height of the water that goes above the levels predicted by the regular astronomical tides.
A storm’s wind pushes water onshore, which is primarily what is responsible for the surge; how strong the amplitude of the surge is can depend on several things, including the size, speed or intensity of the storm and what direction the coastline is oriented towards in terms of the storm’s track.
The local bathymetry – a word which refers to the bed or floor of a body of water – can also have an impact on how high the surge will be. Research here investigates what the impacts of fluctuations in the bathymetry are upon a storm surge.
The storm surge should not be mixed up with storm tide, which refers to the total amount of seawater observed during a storm, the combination of the astronomical tide and the storm surge together.
Since the astronomical tide is determined by the strength of the moon and sun’s gravitational pull, you’ll notice the highest storm tides typically occur in the midst of a storm that also coincides with a new or a full moon.
What are storm surge zones?
As a storm surge can cause huge threats to life and property, you will find that locations prone to having them have plans in place to protect their citizens.
A Storm Surge Planning Zone refers to an area where life or property might be affected by a storm surge that is one and a half feet or higher.
The zones will be created using Sea Lake and Overland Surge from Hurricanes – or SLOSH, as it is amusingly known – model grids, which utilize physical features including coasts, rivers, bays, bridges and general water depth.
When a threat has been identified, each zone – or specific parts of a zone – will then be evacuated in accordance with who is closest to the track of the storm and its predicted surge. In most places, there are typically five zones, identified as follows:
- Zone A – greatest risk for storm surge during Category 1 storms and higher
- Zone B – risk of storm surge in Category 2 storms and higher
- Zone C – risk of storm surge in Category 3 storms and higher
- Zone D – risk of storm surges in Category 4 storms and higher
- Zone E – risk of storm surges in Category 5 storms
In the event of a storm surge that merits evacuation, it is imperative you know whether or not you are living in a designated evacuation zone.
For instance, in the state of Florida, you can use this search engine to find out where your evacuation zone is, and plan any travelling you might have to do ahead of time.
How far does storm surge travel?
The distance a storm surge moves depends on the category of the storm that is occurring, as well as several other factors.
Once a storm surge reaches the land, the giant wall of waves is capable of moving for miles inland, destroying anything that gets in its way. It can eventually move for tens of miles away from the shoreline.
Why is a storm surge so deadly?
The giant waves of ocean water created as a result of storm surges are to blame for the majority of deaths during deadly hurricanes, including during the horrific Hurricane Katrina back in 2005.
These storm surges can send thirty foot floods inland, wiping out people, properties… just about anything in their wake.
Though different to the walls of water caused by tsunamis, these are equally as destructive, weighing approximately 1,7000 lb per cubic yards. Entire beaches can be eroded, inland rivers and lakes can be flooded, skyscrapers can be brought tumbling to the ground.
The sudden changes and rapid development of hurricanes can create surges that cause levels of destruction the likes of which the world has never seen – it all depends on the weather, the wind, where on the map the surge is taking place and probably a bit of pure luck, too.
So, not only can catastrophic damage be done to infrastructure, buildings and bodies of water on land, but surges are also responsible for thousands of deaths every time one occurs.
How can storm surge be prevented?
Although it is impossible to stop a storm surge, because they are natural occurrences caused by things we humans cannot control, we can make adjustments that should prevent them from causing as much damage or taking away as many lives.
These include the implementation of structures by governments or communities generally, for instance constructing hard infrastructure such as a surge barrier or soft infrastructure like mangroves or coastal dunes.
Other helpful preventative measures include improving the practise of coastal construction more generally, as well as utilizing social strategies such as early warning systems, predetermined evacuation zones and routes, and better education about storm surges more generally.
In terms of preparation the average person can do, it is important that you:
- Check your entire house and land (your whole property) for possible dangers in the event of a flood, repairing any vulnerabilities you find
- Check all of your supplies, primarily for food, medications, batteries, flashlights and a radio not dependent on electricity
- Learn how to shut off your home’s gas and electricity systems as local authorities may instruct you to turn these off
- Make sure your whole family has an emergency plan for the event of a surge and that everybody knows where they should be during one
Is a storm surge a natural disaster?
The storm surges themselves are not technically considered natural disasters, because they are simply a consequence of other events happening, like hurricanes, which are indeed natural disasters.
That being said, they are an incredibly dangerous side effect of such catastrophes and their ability to destroy should not be underestimated.