Katrina's Surge, Part 15

A Weather Underground 16 part series about Hurricane Katrina, by Margie Kieper.

For this second week of September, we continue to travel the coastline destroyed by Hurricane Katrina's record storm surge. This is something that has never been shown on the news or talked about, either in the overall, or in detail. What you'll be seeing here is what people on the Gulf Coast have been calling the “Invisible Coastline” for almost a year now.

Today we look the section of eastern Jackson County, that contains the main communities of Pascagoula, Moss Point, and Escatawpa, as well as a number of smaller ones.

From Google Maps, the location of this area along the Gulf of Mexico coastline impacted by Katrina:

Pascagoula, Jackson County, MS

Image courtesy of Google Maps

The surge in this coastal area ran from 18 feet on the west to 16 feet on the east, with wave runup fairly far inland. This area, like many areas along the Mississippi coastline, was completely inundated almost up to Interstate 10. Surge ran up the river estuary, with bayous of Gautier receiving a maximum of fifteen feet on the west, and areas of Moss Point and Escatawpa receiving from nine to fourteen feet. Flooding was extensive well up the river basin, and also along the Escatawpa river and the many bayous. Pascagoula and Moss Point, which are surrounded by water features on all sides, were almost completely inundated, except for small areas of high ground. These cities had the GOM on the south, the Pascagoula River estuary on the west, the Escatawpa River to the north, and various bayous and areas of protected marshland to the east. Communities along the river such as Gautier and Vancleave were also extensively flooded. Further to the east, areas that flood in just a heavy rainstorm, such as Grand Bay, Alabama, received extensive flooding as well.

Here a Mapquest image shows the area in more detail:

Mapquest – Ocean Springs to Gautier

Image courtesy of Mapquest

And here is the FEMA surge inundation map showing how much of the area was submerged:

FEMA Jackson County, MS surge inundation detail

Image courtesy of FEMA

For some reason I haven't been able to figure out, quite a bit of the "unflooded" area on the map around Hwy 90 to the northeast of Pascagoula proper (the small white area on the map), did flood, but was not indicated so on the above FEMA map -- and on the USACE HES maps is labeled a Cat 4 surge area. The Cat 4 surge did not extend this far east, so that's got to be mislabeled and likely a lower elevation than previously mapped. On the FEMA detailed inundation maps it is correctly identified as being mostly submerged, and that would have been due to their LIDAR data used to generate those maps. Just about the only area that didn't flood around there was the part of the hospital that is built high, and I think perhaps the fairgrounds and around that area.

It's very strange to write this entry, and I'm glad to have it almost last. It's odd to think of every single place in the city where I grew up, all those years, under so much water that day: the house we were raised in, the elementary, junior high, and high schools, the homes of all my friends, the beautiful homes along the beach and nestled cozily along Washington Avenue, where I biked daily, the shipyard where so many of the townspeople work, businesses, hotels, restaurants, city offices, all of it. Some incredible number of Pascagoula's residences were flooded -- something like 95% of the total homes in the city. There was wave action of over a foot all the way north in the Pinecrest subdivision, where I grew up. The flood images you'll see were taken inland near the eastern I-10 interchange, and there's wave runup there.

Here are some NOAA aerials of the Pascagoula area; first the large shipyard and refinery, then an area of the town close to the beach. Pascagoula, like Waveland, is almost all completely south of the old coastal road, Hwy 90.

NOAA aerial image NOAA aerial image NOAA aerial image

Images courtesy of NOAA

Zooming in, we see the familiar swath of debris along the shoreline. Here are two different areas of Beach Blvd and an area just inland, followed by what used to be forty condos on Spinnaker Point. Beach Blvd runs the width of the city.

NOAA aerial image NOAA aerial image NOAA aerial image NOAA aerial image

Images courtesy of NOAA

Here is a photo I took in March, of the remaining Spinnaker Point condo that is seen in the above aerial image, owned by Melanie Bosarge (I heard finally that is all torn down now, and they will do something else with the land).

Pascagoula Spinnaker Point

This is some 80-odd miles from the center of where Katrina made landfall. Again, the scope of destruction from this hurricane is so beyond anything that this series of blog entries can articulate.

I recently found this satellite image showing the size of Katrina at landfall. At this time the core of the storm's strongest winds stretched all the way from Slidell to Mobile Bay (winds on the western side of the storm were much attenuated due to entrainment of dry air in the day before landfall).

Katrina at landfall

Here's an image of what's left of a house that faced Beach Blvd, taken from Washington Avenue. I was able to take the shot because the second home, and trees, that used to face Washington are gone.

Pascagoula damage

Here are some additional photos of damage around the area:

Pascagoula damage Pascagoula damage Pascagoula damage Pascagoula damage Pascagoula damage

This is what had to be done to clear most of the roads -- and some places, there were homes blocking the streets. In areas closer to the eyewall, such as Pass Christian, a mountain of debris some thirty feet high had to slowly be cleared by the National Guard, using heavy machinery, just to get into the area.

Pascagoula damage

I thought I'd mention something interesting that I found online: a Moss Point teenager, Elizabeth Beatty, documented her story of life after Katrina.

Here's another response to the question, "Why don't they move away? Why do they move there in the first place?" You can whip out this 1732 map of Pascagoula and ask, "You mean before the 1730s, or after?" It's in French, but so what?

Pascagoula damage

Here are some images of the surge as it engulfed the eastern part of Jackson County:

Pascagoula surge Pascagoula surge Pascagoula surge

Some thoughts on wind and water: Here is an image of the Pascagoula Emergency Operations Center (EOC). The roof partially came off during Katrina. Just as that was occurring, a wind gust of 137 mph was measured. This wind gust did not make it into the unofficial record from the EOC because it was not valid, as it was occurring the same time as the structural failure.

Pascagoula EOC

The Bernoulli effect is, among other things, where the velocity of fluids can be increased as they are funneled through smaller spaces. It resulted in a stronger current in some areas receiving surge as the surge was funneled in-between tall buildings like the casino hotels, in Biloxi, for example. The same thing happens with air. This is a familiar phenom to anyone spending time in a high-rise of a city. Recently during a dramatic hailstorm in Minneapolis, I watched a very dense pocket of nickel-sized hail being blown upwards over at least fifty feet, from the twenty-seventh floor of a building downtown. Anyway -- wind coming off of a taller building can eddy and have an increased velocity relative to what is blowing overhead. Many personal weather stations are unknowingly located where this effect can enhance actual windspeeds that are occurring.

Here's why the EOC received winds so much higher than what were actually occurring: The courthouse building, sitting right next to it (both are on the corner of Magnolia and Convent, but the larger multi-story building was just downwind of the EOC, with Katrina's onshore winds).

Pascagoula Courthouse

What is unfortunate is that this one-time wind gust, which did not even qualify as a valid measurement, and which was completely unrepresentative of the winds experienced with Katrina, has been put on several plaques and posted in completely different areas of the county. It was not even qualified as a wind gust vs. sustained winds (which are always much lower). The highest valid unofficial gust from the EOC is documented as 108 kt (124 mph). These measurements from EOCs are unofficial because they are not from NWS stations, where anemometers are mounted at a standard height and usually free from obstructions, in order to provide accurate wind measurements.

The FIU wind tower set up at Trent Lott airport, 9 mi inland, had a max one-minute wind of 64 kt / 74 mph, and the USA mesonet, which was set up right in Pascagoula, had a max one-minute wind of 58 kt / 67 mph, and a peak gust of 66 kt / 76 mph.

Sustained one-minute winds of 64 kt is the lowest threshold that qualifies as Category 1 windspeeds. So, only because of the one 64 kt measurement, is there even evidence that Pascagoula received hurricane-force winds, and the absolute minimum at that.

I have no doubt that Category 1 winds occurred in the eastern part of Jackson County, but there is no evidence to support anything higher.

Wind gusts can commonly reach almost as high as twice the sustained windspeed, once over land, due to turbulence in the boundary layer as the storm moves inland, from friction with the rough profile of land, as opposed to the open ocean. What that means, is that one or more gusts up to around 130 mph were possible, in any given location. Because of the location of the EOC, the windspeed measured there is clearly higher than the speed of the gust that produced it, but certainly could have been a gust over 100 mph. And here and there it is certainly possible that a gust of a few seconds higher than that did occur. This is not the same as saying that the storm had 137 mph sustained wind speeds.

What is even worse, the surge height is listed as what was measured at the EOC (around 16 feet), when the surge height in the western part of the county was on the order of 22 feet, and, along Beach Blvd in Pascagoula, on the western end, 18 feet.

So people will believe the winds were about twice as high as they were, and will not realize how high the surge was, in Jackson County. Years from now, no one will remember the correct numbers, but those plaques will be out there.

From a scientific point of view, it is always important to be as accurate as possible. But from the ordinary person's perspective -- things were so extreme already; why exaggerate them? People need to know that 70 mph winds can do quite a bit more damage than they think. And they need to understand the power of moving water. I have images that I haven't posted of huge concrete buildings reduced to ruin by the surge, wanting to show things on a more personal level. Nothing, but most especially a home, is built, or can be built, to withstand surge, except perhaps a specially-constructed concrete bunker with no windows.

Below you can see images of the Baptist Assembly building that was supposedly hurricane-proof but was razed where it sat on Henderson Point (many times "hurricane-proof" is touted for buildings that are mistakenly built for wind, not water, in areas vulnerable to surge). Notice the lower two floors have been completely washed out by the force of the surge, taking walls and everything except the concrete infrastructure and supports. Another is the Biloxi aquarium building on Point Cadet, with the walls where the surge pushed through reduced to a pile of concrete rubble.

Baptist Assembly building, Henderson Point, Pass Christian Scott Aquarium, Point Cadet, Biloxi

If these buildings didn't survive, how can your home be a safe haven.

If looking at these images along this long stretch of coastline has anything to tell us, it is to be aware of the power of storm surge, and the inevitability of destruction where surge occurs. You can't stop it, and you aren't safe from it. The Sun Herald recently ran a series of stories on people who were lucky enough to survive the surge. There were some common and representative misconceptions that were touched on in these stories:

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

How? No one will be able to get to you. Water rises quickly -- six to ten feet within minutes; cars can't drive in it, and it is usually unnavigable by boats when it is coming ashore.

--Just stuff towels under the doorjambs. Then rush around to start picking up things that are close to floor level, so you can save them.

Bad idea. In a minute or so the surge will burst open the door, and instead of standing in a room with four inches of water, you'll be knocked off your feet and into whatever piece of furniture is closest, and will suddenly be in three or four feet of moving water that you can't make any headway into...just before the refrigerator, quickly rushing through the water towards you, knocks you cold.

--You'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 surge can be equivalent to a Class III or IV rapids (Class V is hardly navigable by expert kayakers and canoers, and Class VI is not navigable at all).

--You'll know in time.

Usually not. As I said, surge comes on little cat feet. Most people that were not completely taken by surprise simply happened to look out the window at the right time.

People who survived did one of several things: they floated out an open window, and managed to hang onto debris, a tree, or some other structure above the water, until the surge receded, hours later. Or, they were able to pull themselves into an attic, or make it up to a second floor, where water did not reach, and luckily the home was not swept away.

In some areas of the country, where people live in flood plains near rivers, and behind levees, for example the Grand Forks / Fargo area of Minnesota and North Dakota, it is common to have an axe fastened to the wall of the attic. Then, if water comes in unexpectedly, and, always, quickly, and if you have time to make it into the attic, you can get out and onto the roof without drowning, if you have time to hack a hole in the roof.

The best thing is to leave before the surge arrives. You may feel safest in your home, but no one's home is a match for moving water.

The last entry in this series, covering Mobile County, Alabama, including Dauphin Island, will be out sometime this week. I'll also mention the remarkable things that Katrina did to buoys in the Gulf, and address the question, were people properly warned of the surge danger?

Hurricane Katrina Storm Surge:

Weather Underground Storm Surge Articles

Storm Surge Safety Actions

  • Minimize the distance you must travel to reach a safe location; the further 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 route. Do not get on the road without a planned route, or a place to go.

  • Choose the home of the closest friend or relative outside a designated evacuation zone and discuss your plan with them before hurricane season.

  • You may also choose a hotel/motel outside of the vulnerable area.

  • If neither of these options is available, consider the closest possible public shelter, preferably within your local area.

  • Use the evacuation routes designated by authorities and, if possible, become familiar with your route by driving it before an evacuation order is issued.

  • Contact your local emergency management office to register or get information regarding anyone in your household whom may require special assistance in order to evacuate.

  • Prepare a separate pet plan, most public shelters do 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.

  • Take all prescription medicines and special medical items, such as glasses and diapers.

  • If your family evacuation plan includes an RV, boat or trailer, leave early. Do not wait until the evacuation order or exodus is well underway to start your trip.

  • If you live in an evacuation zone and are ordered to evacuate by state or local officials, do so as quickly as possible. Do not wait or delay your departure, to do so will only increase your chances of being stuck in traffic, or even worse, not being able to get out at all.

  • Expect traffic congestion and delays during evacuations. Expect and plan for significantly longer travel times than normal to reach your family's intended destination.

  • Stay tuned to a local radio or television station and listen carefully for any advisories or specific instructions from local officials. Monitor your NOAA Weather Radio.

Source: NOAA