Katrina's Surge, Part 5

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

For the remainder of the month, we're traveling 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's journey takes us to St. Bernard Parish, which has the horrific distinction of being the only parish or county completely inundated from Katrina. Most of the parish was flooded directly from the surge, in the early dawn of August 29th, 2005, but the section that was spared was subsequently flooded in midmorning, along with NOLA's Ninth Ward, when the Industrial Canal levee walls failed. And, similar to Plaquemines, the water had no way to drain out of the parish immediately afterwards.

Violet LA

Image courtesy of Google Maps

Out of the thousands of buildings in the parish, only a handful were salvageable afterwards. Out of 26,900 homes, less than a half dozen were left habitable. Think about that number; some of you reading the blog may not be living in a city with that many residences.

St. Bernard Parish, like Plaquemines Parish, meets the Gulf with a spiderweb of marshland, made more fragile every year by the many canals that have been built and that modify the natural flow of water over the wetlands:

Mapquest -- St. Bernard Parish

Image courtesy of Mapquest

Especially controversial is the Mississippi River Gulf Outlet (MRGO, aka "Mister Go"), which was built over the objections of the parish, was never utilized for anywhere near the amount of traffic it was designed for, and was constantly being raised as an issue of concern with regards to hurricane surge.

The consensus after extensive studies is that water was funneled to the west through MRGO and into the Gulf Intracoastal Waterway (GIWW), contributing to the levee breaks at the Industrial Canal.

Like Plaquemines Parish, St. Bernard is protected on practically all sides by various levee systems. A large portion of the parish is below sea level. The most substantial levee is the one along the Mississippi River, and this levee did not fail during Katrina. West of the parish lies the Ninth Ward of Orleans Parish, and the levee walls of the Industrial Canal. Running northeast of the Industrial Canal, a series of levees along the GIWW bordered St. Bernard along the north. Levees along MRGO ran NW to SE along the eastern side of the parish. Another set of levees ran east-west to the south of the line of populated communities, meeting with the levees along the Mississippi River.

St. Bernard was first flooded from the east and north as the levees were overtopped and damaged (MRGO levees sustained the heaviest damage from the storm). After the break in the Industrial Canal, water poured in from the west.

The IPET report contains high water marks (HWM) for St. Bernard as follows (heights have been approximated here):

  • 14 ft at the Industrial Canal
  • 15 ft along GIWW levee
  • 18 ft where MRGO meets GIWW
  • 21 ft MRGO levee midway
  • 19 ft MRGO levee south
  • 17 ft inland of that, to the west
  • 11 to 13 ft running W to E, in a line south of the populated areas, inland, along the east-west levee
  • 10 ft along the MS river levees

This FEMA map shows the extent of the parish that was flooded (the yellow area), and the part that was not flooded (the light green area...basically too small to see on this scale):

FEMA St. Bernard Inundation Map

Image courtesy of FEMA

Eyewitness accounts indicate the water rose extremely quickly, trapping many people in their homes. Here is an eyewitness account from Chalmette, a city on the western end of St. Bernard, from the IPET report:

This eyewitness reported that power went out about 0500 on Monday morning Aug 29th 2005. She saw rainwater in the street, but no floodwater at about 0800. Sometime shortly thereafter the floodwaters came and in about 15 minutes they were up to the ceiling in the lower floor. They stayed at that level for about 10 days. The wind abated about 1600 hrs, which is approx when they could get a boat to rescue her and her husband and son. She stated that they have 10-foot ceilings in the house. She has videos and will share when she is able to get them copied. All clocks in the house stopped around 9:05, being about 8 feet above the floor. The water was black in appearance.

The water that flooded St. Bernard was contaminated by a very large oil spill -- millions of gallons -- from a storage tank in the industrial portion of the parish. Also, after the water was pumped out, the parish had over a foot of oily mud remaining. This made cleanup in St. Bernard more complicated and difficult than in other locations, after the storm.

Below is a NOAA aerial image of Violet, in St. Bernard Parish, followed by a USGS image of the typical structure that remained after marinating for several weeks in the toxic water mixture.

NOAA Violet LA

Image courtesy of NOAA

USGS St. Bernard Parish

Image courtesy of USGS

A very detailed and complete description of where things stand in St. Bernard was just published a couple days ago, on August 14th, titled Struggling to Survive after Katrina, by Jonathan Rauch, and can be read in full at ReasonOnline. Some of the extraordinary excerpts from this article are below:

A year after the storm, St. Bernard Parish is struggling to survive. The recovery has gone little better than the initial response. The deluge of water was followed by an alluvium of indecision and a blizzard of red tape.

On most blocks one encounters no people, hears no human sounds. There are no dogs or cats. The odd car prowls by, picking its way amid potholes. By day, people come and work on their houses. By night, the sense of desertion is overpowering. Even a graveyard feels less desolate, because it is not meant for living.

"There was not a livable house in this parish," says Henry J. (Junior) Rodriguez, the 70-year-old parish president. Officials say that only 40 to 50 structures escaped serious water damage; five or six homes, out of 26,900, were inhabitable.

Everyone in St. Bernard has a story, but it is the same story: I lost my home and everything in it.

Before Katrina, the parish's population was 67,000. Today, parish officials estimate that 20,000 people are present during the day, and 8,000 to 10,000 by night, though many locals say those numbers seem high.

Asked if the community can reassemble itself, Vaughn says, "The longer it goes, the more I would have to say it's shattered. It's just taking too long." Others offer much the same assessment. "It's going so slow it's unbelievable," says Larry Ingargiola, the director of the parish's office of homeland security and emergency preparedness.

Below is another of the NOAA aerial images showing the flooding in Chalmette. The link is provided to the detailed image. In many of the St. Bernard images, there is blowdown in forested areas; as Katrina moved directly to the east of this parish, it is likely that some strong winds were felt in the rural eastern areas, from the northern eyewall (on the order of Cat 2 or Cat 3 intensity).

NOAA Katrina Images Chalmette

Image courtesy of NOAA -- link

Storm Surge -- Modeling:

The model used by the USACE in the IPET report to hindcast Katrina's storm surge is the ADCIRC model for southeast Louisiana. Below are some frames from the hindcast (values moving towards red and fuschia indicate high surge values).

ADCIRC Katrina hindcast

Image courtesy of ADCIRC

The IPET report, in one of the appendices (IV-5-28 to IV-5-30), has a writeup of the ADCIRC hindcast, focusing on the effects in Louisiana (link to the report to view the referenced diagrams):

Description of the Physics of the Hurricane Katrina Storm Surge

The progression and physics of the Katrina surge event is shown in a sequence of surface water elevation contour maps with superimposed wind vectors (knots) between 8/29/0700 UTC and 8/29/2300 UTC shown in Figure 5-7a to 5-7k and with water currents (ft/s) in Figures 5-8a to 5-8k. A more detailed view of the surface water contours and currents showing Lake Ponchartrain and metropolitan New Orleans is shown in Figures 5-9a to 5-9k. It is clear that storm response over southern Louisiana is highly localized and varies rapidly over even a few kilometers. Surge is dominated by physical features such as levees, river berms, raised roads as well as by breaks in these features, inlets, channels and rivers. Furthermore the shallower the water, the more effective a given wind stress is at increasing surface water gradients and in piling up water against obstructions.

On 8/29/0700 UTC (2:00 a.m. CDT) Katrina has just been downgraded to a Category 4 storm with the eye approximately 80 miles south of the initial landfall location. Figures 5-7a, 5-8a and 5-9a show the predominantly easterly winds blowing water into Breton and Chandeleur sounds as well as into Lake Borgne. In particular, water is being stopped by the Mississippi River levees and by the St. Bernard/Chalmette protection levee where surge is building up to 10 ft.

Water level is also raised on the southwest end of Lake Pontchartrain where the railroad berm holds the water while water levels are suppressed in eastern Lake Pontchartrain. The combined water level rise in Lake Borgne and the drawdown of water in eastern Lake Pontchartrain causes a strong surface water gradient across the inlets which connect these two water bodies, Chef Menteur Pass and the Rigolets Strait. This gradient moves a current which drives water into Lake Pontchartrain which is further reinforced by the easterly winds. This process initiates the critical rise of the mean water level within Lake Pontchartrain. Finally, note that the predominantly easterly and northerly winds to the west of the Mississippi River force a drawdown of water away from the west-facing levees in these regions.

On 8/29/1000 UTC (Figures 5-7b, 5-8b and 5-9b) Katrina is located 30 miles south of its initial landfall location and the winds over the critical regions are still predominantly from the east. Surge is building up to more than 18 feet along the Mississippi levees between Buras and Pointe A La Hache.

On 8/29/1100 UTC (Figures 5-7c, 5-8c and 5-9c) Katrina is nearing landfall and surge continues to build up against the levees of lower Plaquemines Parish reaching elevations up to 19 ft. The surge in this region has started to propagate up the Mississippi River and also extends broadly into Breton Sound. Further north, surge continues to build up against the St. Bernard/Chalmette protection levee due to the now north-easterly winds, up to 13 feet.

On 8/29/1200 UTC (Figures 5-7d, 5-8d and 5-9d), the eye location has caused a significant shift in the wind patterns. Surge has started to be blown off the southernmost east-facing levees of Plaquemines Parish although surge continues to build up further north along the river levees. Surge has now reached 16 ft along the St. Bernard/Chalmette protection levee and is being driven through the GIWW into the IHNC and Lake Pontchartrain. In addition, the northeasterly winds over Lake Pontchartrain are building up surge against the lake levees of Jefferson Parish and Orleans Parish. In addition the continued strong surface water gradient aided by the winds between Lake Borgne and Lake Pontchartrain continue to drive water from Lake Borgne into Lake Pontchartrain. This process is still enhanced by the drawdown in the northeast corner of Lake Pontchartrain.

On 8/29/1300 UTC (Figures 5-7e, 5-8e and 5-9e), the surge that built up against the lower Mississippi River levees is rapidly propagating in a north-easterly direction towards the Chandeleur Sound. The component of the surge propagating up the Mississippi River reaches 16 ft. Surge is now also being driven from the west in southern Plaquemines Parish near Venice. Surge is peaking along the St. Bernard Parish/ Chalmette protection levee and in the funnel defined by levees along the GIWW and the MRGO. Within Lake Pontchartrain, surge is now strongly focused on the south side of the lake and a well defined drawdown exists along the north shore. It is noted that surge has not built up along the concavity in the Mississippi River along English Turn, due to the change in the direction of the winds.

On 8/29/1400 UTC (Figures 5-7f, 5-8f and 5-9f), Katrina is now located over Lake Borgne. The surge originating along the levees of lower Plaquemines continues to propagate across Chandeleur Sound towards the Mississippi Sound in a northeasterly direction. Surge is attenuating along lower Plaquemines on the east side of the river as is the surge that is propagating up the Mississippi River itself, due to winds from the west and north. Water continues to pile up from the west along the levees near Venice. Surge along the St. Bernard/Chalmette protection levee and in the GIWW/MRGO funnel are attenuating. Water is being blown from the north of Lake Ponchartrain and continues to build up along the southern shores of Lake Pontchartrain to around 9 ft. Water is accumulating from the east and overtopping the CSX railroad between Lake Borgne and Lake Ponchartrain.

On 8/29/1500 UTC (Figures 5-7g, 5-8g and 5-9g), Katrina continues to move north. The surge that propagated from Southern Plaquemines Parish has now combined with the local surge being generated by the strong southerly winds and is dramatically increasing water levels between Bay St. Louis and Biloxi with peaks reaching 24 ft. Water is blown from the west to the east in Lake Ponchartrain. In addition water is overtopping the CSX railroad west of Lake Borgne and the Mississippi Sound. Water is also driven in a westerly direction across Mobile Bay.

On 8/29/1600 UTC (Figures 5-7h, 5-8h and 5-9h), Katrina is near its second landfall. Surge along the State of Mississippi shoreline is spreading inland and continues to build up driven by the winds from the south to levels reaching 29 ft. Water still is being blown from west to east across Lake Ponchartrain and water continues to move from Lake Borgne into Lake Ponchartrain from the east, overtopping the CSX railroad and U.S. 90.

On 8/29/1700 UTC (Figures 5-7i, 5-8i and 5-9i), surge continues to propagate inland along the State of Mississippi shore. Winds are still blowing from the west across Lake Pontchartrain causing a drawdown in the west and a surge in the east and water very forcefully penetrates from Lake Borgne.

On 8/29/20 UTC (Figures 5-7j, 5-8j and 5-9j), Katrina has moved well inland. Surge along the State of Mississippi coast is subsiding. However high water remains in Lake Pontchartrain as well as Lake Maurepas. In addition, water is withdrawing from Lake Borgne. This process continues as is shown on 8/29/23 UTC (Figures 5-7k, 5-8k and 5-9k). However note that Lake Pontchartrain is at 7 ft and is only slowly subsiding due to the lack of strong water surface elevation gradients between Lake Pontchartrain and Lake Borgne.

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

Hurricane Preparedness

National Hurricane Center

Centers for Disease Control & Prevention