Know the Basics

A storm surge is water that is pushed onto shore by a hurricane. It is rarely a "wall of water" as oftentimes claimed, merely rather a rise of h2o that can exist as rapid as several anxiety in just a few minutes. The tempest surge moves with the forrad speed of the hurricane —  typically 10-15 mph. This wind-driven water has tremendous power. One cubic yard of bounding main water weighs 1,728 pounds —  almost a ton.

This means a one-foot deep storm surge tin sweep your car off the road, and even a 6-inch surge is difficult to stand in. Compounding the destructive power of the rushing water is the large amount of floating debris that typically accompanies the surge. Trees, pieces of buildings and other debris float on top of the tempest surge and act equally battering rams that can cave in whatever buildings unfortunate plenty to stand in the way.

Staying Prophylactic

If you lot receive an evacuation order for a hurricane tempest surge, it is a good idea to go out sooner rather than later. The storm surge can begin to ascension a day before the storm hits, cut off escape routes when low-lying highways are flooded. This is particularly true along the Gulf of United mexican states shore. If you live about the sea, the storm surge is the most dangerous part of a hurricane's hazards. The high death tolls of theten deadliest U.Due south. hurricane disasters, including the Galveston Hurricane of 1900 (over viii,000 killed), the Lake Okeechobee Hurricane of 1928 (2,500 killed), and Hurricane Katrina of 2005 (1,833 killed), were primarily due to the storm surge.

Hurricane Katrina's storm surge pours over the 8-foot high north levee of the MRGO/Intra-Littoral Canal, directly nether the Paris Road Span in eastern New Orleans. The photo was taken by Dan McClosky, the manager of Entergy's Michoud Ability Institute. Mike Collins of Austin, Texasput together a nice in-depth clarification of this photo, which was judged equally being authentic on the hoax debunking web sitesnopes.com.

Contributing Factors

There are iii mechanisms that contribute to the storm surge

  1. The action of the winds piling up water (typically more than than 85% of the surge)
  2. Waves pushing water inland faster than it tin can drain off. This is called wave set-up. Wave set-up is typically 5-10% of the surge
  3. The depression pressure level of a hurricane sucking water higher into the air near the center (typically v-10% of the surge)

The storm surge depends greatly upon the size and intensity of a hurricane, the angle that it approaches the shore at, how deep the water is close to shore (the slope of the seabed at the coastline) and how fast the hurricane is moving. Learn more about storm surges with Jeff Masters' articles: A detailed view of the storm surge: comparing Katrina to Camille and General characteristics of storm surges.

Delineation of a 15-pes hurricane storm surge occurring at high tide of two feet well-nigh mean bounding main level, creating a seventeen foot storm tide. Note that there are 10-foot waves on meridian of the 17-human foot tempest tide, so the external loftier water mark (HWM) left on the outside of structures by this hurricane could be 27 anxiety or higher. Prototype credit: NOAA SLOSH Display Training Transmission (PDF File).

Defining Storm Tide, Storm Surge and High Water Mark

The tempest surge is how high to a higher place current body of water level the bounding main h2o gets. The number we are most interested in regarding storm surge is how many feet above mean body of water level (MSL) overflowing will occur. This number is known as thestorm tide, not the storm surge. The storm tide is the summit of the storm surge above the MSL, corrected for the tide. For example, in a location where high tide is two feet college than mean sea level, and depression tide is two feet lower than hateful sea level, a 15-pes storm surge would cause a 17-human foot storm tide if the hurricane hit at high tide or a thirteen-pes tempest tide at low tide. Keep in heed that on top of the tempest surge will be large waves capable of causing astringent flooding and battering harm—  these waves are non included in storm surge forecasts.

The waves on summit of the storm tide pause when they reach shallow water and create an externalhigh water marking (HWM) on structures. The loftier water marker tin can exist much college than the storm surge or storm tide. For example, the maximum storm surge of Hurricane Katrina was 27.8 anxiety in Pass Christian, Mississippi (measured within a building where waves couldn't accomplish). However, the highest high water marker was much higher—  34.1 feet on the exterior of a building in Biloxi, Mississippi, where a high tide of almost one foot combined with 11-foot loftier waves on superlative of the 22-human foot storm surge to create the 34.one-human foot high h2o mark.

High water marks on East Ship Isle, Mississippi, after Hurricane Katrina in 2005. Left: Bark stripped off a tree with salt-burned pine copse in the groundwork (note the 25 ft [seven.65 g] long survey rod for scale). Right: Massive beach and over wash erosion illustrated by damaged and snapped pine trees forth the beach. Arrows show the the high water mark left by the storm surge. Image credit: Fritzet al., 2007, "Hurricane Katrina storm surge distribution and field observations on the Mississippi Barrier Islands."

Storm Surge Survival Misconceptions

The storm surge is usually the well-nigh unsafe threat of a hurricane. Those lucky enough to survive Hurricane Katrina'south record storm surge shared their stories, shedding low-cal on some common misconceptions virtually storm surge survival.

Misconception:Call 911 and you lot can be rescued, while the water is pouring into your home.

How? No ane will exist able to go to you lot. Water rises quickly—  sometimes 6-x anxiety within minutes; cars can't drive in it and information technology is usually unnavigable by boats when information technology is coming ashore.

Misconception:  Just stuff towels under the door jambs. Then rush around to get-go picking up things that are shut to flooring level, and then you can relieve them.

Bad thought. In a infinitesimal or so the surge will flare-up open the door, and instead of continuing in a room with 4 inches of water, y'all'll be knocked off your feet and into any piece of piece of furniture is closest. You'll of a sudden be in three or four anxiety of moving water that you lot can't make whatever headway into.

Misconception:  Yous'll be able to maneuver around in the rushing water.

Probably not. Some people who drowned were not even able to get out of the room they were in when the water started pouring into the home. The speed of water in a surge tin can be equivalent to Class III or Four rapids (Course V is hardly navigable even by skilful kayakers).

Misconception:  Y'all'll know in time.

The surge is usually non a wall of water as is often causeless but rather a rapid rise of water of several feet over a period of minutes, meaning information technology can sneak in unexpectedly.

Misconception:  You tin can outrun the storm surge in your auto.

Here's an email sent to Weather Underground from a resident in the Florida Keys during the Keys evacuation gild for Hurricane Ike in 2008

I hate to bother you again, just nosotros live on Marathon in the Florida Keys on the Atlantic side, and my married man says that if we see water coming upwards from storm surge and have an inch of water in our firm, that we can outrun the storm surge in our motorcar. Tin can you please tell me if there is any way this tin can perchance be true? P.S., I don't know of anyone who lives downwardly hither who is planning on evacuating for Ike. Everyone says they are staying.

If you lot wait until the water is an inch high before trying to outrun the surge, the odds are that the surge will rise to over a pes high before you become your car out of the driveway. If the h2o is a foot high, the typical x-15 mph speed of the storm surge's current has enough force to sweep a car away. In many places along the coast such every bit the Keys, there is only i road out of a low-lying region prone to storm surges. In such cases, the storm surge will probable be moving perpendicular to the road, cutting off the only escape route.

A man wearing a tiny life jacket and clutching a neon green noodle and a pet dog floats on the remains of a house in Waveland, Mississippi, during Hurricane Katrina. The photograph was taken from the 2d floor window of a dwelling, and the water is close to the roof line of the get-go floor. The home was at an elevation of nigh 17 anxiety and the surge is close to 10 anxiety deep here. There are electric lines running down from a pole to a home from left to correct. In the distance on the right is a home with water up to the roof line. The photograph was taken by Judith Bradford. Her husband, Bill Bradford, swam out and rescued the man and his dog, and ii other people who floated by. The paradigm in a higher place is described in more detail on Margie Kieper'south Katrina tempest surge web folio.

How to Survive a Tempest Surge

It is common in many flood-prone regions backside levees to keep an axe fastened to the wall of the attic. Then, if water comes in unexpectedly, yous tin can get into the cranium and chop a pigsty through the roof to escape. Don't forget to proceed a length of rope in that location that you can use to tie yourself to a sturdy part of the house (justdon't necktie yourself to the steel beams of the business firm every bit these will sink).

The best way to survive a storm surge is to heed evacuation orders and leave before the surge arrives!

Storm Surge Rubber Actions

  • Minimize the distance you lot must travel to reach a safe location; the farther you drive the higher the likelihood of encountering traffic congestion and other problems on the roadways.
  • Select the nearest possible evacuation destination, preferably within your local area, and map out your road. Do non get on the road without a planned road, or a place to get.
  • Choose the home of the closest friend or relative exterior a designated evacuation zone and discuss your program with them before hurricane season.
  • You may also choose a hotel/motel outside of the vulnerable area.
  • If neither of these options is bachelor, consider the closest possible public shelter, preferably within your local expanse.
  • Use the evacuation routes designated past authorities and, if possible, become familiar with your route by driving it before an evacuation society is issued.
  • Contact your local emergency management office to annals or become data regarding anyone in your household whom may require special assistance in order to evacuate.
  • Gear up a separate pet plan as most public shelters practise not accept pets.
  • Prepare your home prior to leaving by boarding up doors and windows, securing or moving indoors all yard objects, and turning off all utilities.
  • Before leaving, fill your car with gas and withdraw extra money from the ATM.
  • Accept all prescription medicines and special medical items, such as spectacles and diapers.
  • If your family unit evacuation plan includes an RV, boat or trailer, get out early on. Do non wait until the evacuation social club or exodus is well underway to beginning your trip.
  • If you lot live in an evacuation zone and are ordered to evacuate by land or local officials, practice and so as quickly every bit possible. Do not expect or delay your departure, to do so will only increase your chances of existence stuck in traffic, or even worse, not being able to get out at all.
  • Expect traffic congestion and delays during evacuations. Look and program for significantly longer travel times than normal to reach your family's intended destination.
  • Stay tuned to a local radio or television station and heed carefully for any advisories or specific instructions from local officials. Monitor your NOAA Conditions Radio.

Know Your Summit

If yous live nearly the coast, or are thinking of buying property near the declension, it's very much in your fiscal and survival interests to know exactly what elevation your dwelling house is at. If you are a home possessor, your overflowing insurance certificate should tell y'all what your elevation is, based on the best available USGS surveys for the area. In some cases, though, this information is non very precise. For example, in the New York City surface area, elevations as of 2008 on USGS topographic maps were simply surveyed to an accuracy of ten feet. Forth the Hudson River and some portions of Long Island, the accurateness was only twenty feet. These topographic maps have a considerable error range, too, with 90% of the data rated as accurate to plus or minus one-half the contour interval. This means that ninety% of the points forth a 10-foot contour line lie in the 5-15 foot range. This is a pretty broad range if you're trying to approximate your vulnerability to a tempest surge. Efforts are existence fabricated in many areas to perform loftier-resolution mapping using light amplification by stimulated emission of radiation measurements from aircraft combined with GPS. These data sets by and large have an accuracy of 0.15 meters (half-dozen inches), but the information is limited in coverage and difficult to discover on the Cyberspace. Probably the all-time solution is to apply existing low-resultion information (iii-xxx meters in the U.South.) and interpolate the data to your location. Keep in mind that the errors volition often be large using these techniques. Below are some ways yous tin decide your home's elevation.

The current all-time available pinnacle source information for the USGSNational Elevation Dataset over the mid-Atlantic region. Lidar data typically has an accuracy of 0.15 meters. Image credit: Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region report by the U.South. Climate Science Program.

Higher Accurateness

    Rent a surveyor to get an pinnacle accurate to an inch. Cost: $200-$500.
  • Loftier-accuracy lidar information is available at the NOAA Coastal Services Center. The sea level ascent viewer allows you lot to visualize community-level impacts from coastal flooding and bounding main level rising.
  • United States Geological Survey (USGS)National Elevation Dataset. Accuracy: 3-xxx meters. A zoomable interactive map lets you click on your location and encounter the interpolated elevation. Don't exist fooled though, when you lot click and see an elevation of v.28 feet in a region where the resolution of the data is just 10 meters (ane/3 arc second, 33 feet). The real height could easily be ane human foot or thirty feet.
  • EPA ocean level rising pages for the U.S. Atlantic declension. Shows the modeled areas of elevations below 1.5 meters and 1.5-2.5 meters. No roads are overlaid, so information technology's a fleck hard to tell what cities are impacted.

Bottom Accuracy

  • Google Earth: The best elevation accuracy of Google Earth in the U.S. is 10 meters.
  • GPS: Global Positioning System (GPS) is not a skilful choice since the vertical accurateness of nearly mitt-held GPS units for home utilize is only 15 meters (49 anxiety). If you accept admission to a commercial grade differential GPS system (a minimum of $v,000), one can get an accuracy of a few centimeters.