Katrina’s Surge, Part 4

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 along the remaining 20-mile stretch from the center of Plaquemines Parish, where Katrina made official landfall, north to Pointe A La Hache and Belle Chasse.

Image courtesy of Google Maps

Timeline for the storm: Katrina's winds and surge reached the southern portion of Plaquemines overnight and into the early morning hours on August 29th, with the official landfall occuring at 6:10am near Buras. Since Katrina had a large eye, and technically landfall is when the geographical center of the eye reaches land, at this time the northern eyewall of Katrina had already moved north of this location. Katrina's eyewall reached Belle Chasse shortly afterwards, and at that time NOLA started to feel tropical storm force winds. To the east, hurricane force gusts were being felt as far away as 90 miles from the center of the storm's location, at the Pascagoula EOC.

Note: Because of the asymmetrical windfield, with the western of the storm extremely attenuated, NOLA would only feel the effects of Cat 1 winds for a very short time, but areas to the north and east of the storm would experience higher winds, and for a longer time. Recall that by late afternoon news media had already been able to fly into NOLA and film standing in front of the hanging fabric roof ripped off the Superdome. Dauphin Island, AL, about 85 miles to the east of the landfall point at the LA/MS border, experienced sustained winds above tropical storm force (39 mph or 17 m/s) for 16 hours (5am through 8pm), at or close to hurricane force (74 mph or 33 m/s) for five hours (noon until mid-afternoon), and gusts close to hurricane force for three hours (9am through 11am), followed by gusts over hurricane force for eight hours (noon through 7pm).

Wind information in the 8am NHC advisory (all times in CDT), gathered during the previous hour or so, probably between 6:30am and 7:30am, was reported as follows, and showed the Cat 1 winds being reported in Belle Chasse as the storm moved through:

PASCAGOULA MISSISSIPPI CIVIL DEFENSE REPORTED A WIND GUST TO 118 MPH...AND GULFPORT MISSISSIPPI EMERGENCY OPERATIONS CENTER REPORTED SUSTAINED WINDS OF 94 MPH WITH A GUST TO 100 MPH. BELLE CHASSE LOUISIANA...JUST SOUTHEAST OF NEW ORLEANS...RECENTLY REPORTED SUSTAINED WINDS OF 76 MPH WITH A GUST TO 88 MPH. A LITTLE EARLIER...BELLE CHASE REPORTED A GUST TO 105 MPH. NEW ORLEANS LAKEFRONT AIRPORT RECENTLY REPORTED SUSTAINED WINDS OF 69 MPH WITH A GUST TO 86 MPH.

There were no reports of surge heights, but by this time, early morning, Plaquemines had been completely inundated by surge, and the surge was engulfing St. Bernard Parish and coastal areas to the north (Lake Catherine and Rigolets). However we know that a considerable amount of surge hit Plaquemines Parish from the later observation of the flood gauge north of the landfall point, in Pointe A La Hache, noted in the Slidell NWSFO Katrina report:

PONTE A LA HACHE (BGNL1) 14.14 FT...LAST OB BEFORE GAGE FAILED

Aftermath -- then, and today: Some of the images I wanted to post of this area of Plaquemines had to wait, because the Plaquemines Parish government web site was down most of the evening. But that turned out alright, because I had a hard time leaving Buras and Empire, which were hit so hard by Katrina, and I decided to post some before images of Plaquemines from Google Earth. I also found a very telling blog entry from a myspace user, tacosmama, who has been living in Buras:

even though they're going to build in belle chasse first, the united way has decided that they will definitely rebuild the ymca here in buras, where we are now. who knows when that'll be, we have permission to be here till december already. but one day, at least they will come back. someone hung up signs on the fence outside the school in buras saying to bring back their schools. buras residents have to go to school in boothville, at the school where we have volunteers working right now. and i think maybe the high school kids go to port sulfer?

disasterworld is crazy. and recovery is very, very, very slow.

Tacosmama was posting from an internet cafe in Buras, and that intrigued me. So I surfed and found Emergency Communities Projects, which involved some of the same folks who created the New Waveland Cafe. They have set up the Y Cafe in Buras, which just opened on June 14th of this year, in the ruins of a former YMCA building; Camp Hope in Violet, St. Bernard Parish, LA; and the Made With Love Cafe and Grill, also in St. Bernard Parish. I found this information from their website shocking:

Plaquemines Parish is the last frontier of Hurricane Katrina relief. On June 1, 2006, nine full months after Katrina first made landfall in Buras, Emergency Communities opened the first reliable source of hot meals for residents of the lower, more rural half of this devastated parish.

Image courtesy of Emergency Communities

For nine months after the hurricane there was no source of hot meals in lower Plaquemines, and there still wouldn't be, without this community kitchen. How is it possible that an area of our county can be so forgotten? I recommend visiting their web site, which talks about the continuing need to provide community support, even one year later, and where there is information about donating, and tee shirts, coffee mugs, and postcards you can buy which help benefit disaster victims.

Emergency Communities described Plaquemines as beautiful, and in these before images from Google Earth, it appears to be true. Hopefully levee redesign and rebuilding will make this a safe place to live in future.

Image courtesy of Google Earth

Image courtesy of Google Earth

Here are some images of the northern portion of Plaquemines Parish, again from the parish web site:

Image courtesy of Plaquemines Parish Government

Image courtesy of Plaquemines Parish Government

Image courtesy of Plaquemines Parish Government

Image courtesy of Plaquemines Parish Government

Storm Surge and Shallow Coastlines: Yesterday a description was provided of how surge can be generated at landfall from a column of rotating water that forms earlier, underneath a hurricane, while it is in deep water. This diagram from the LSU WAVCIS website, which is a Google Earth image with bathymetry of the GOM superimposed, shows how quickly the GOM transitions from deep to shallow water, how extremely shallow those coastal waters are, and how close to shore this transition occurs south of LA. This area is rich with MMS oil rigs (the green dots), which contain ADCP sensors that could have documented Katrina's rotating current as she passed through them, but unfortunately the power was shut off when the rigs were evacuated prior to the storm. The image also shows LSU WAVCIS stations in red, NOAA buoys in blue, and NOAA CMAN stations in purple.

Image courtesy of LSU WAVCIS

In a closer view, showing Katrina's approximate path towards southern LA, it can be seen that deep water reaches almost all the way to the shoreline, and at the time that deep water was warm due to a loop current eddy that had moved, that year, very far to the north, providing fuel to maintain the hurricane's intensity. So there was no time for the large and powerful rotating current under the intense storm to disperse prior to inundating the coastline, once it was pulled up onto the shallow continental shelf.

Base image courtesy of LSU WAVCIS -- closer view, overlaid with Katrina's path

The bulk of Katrina's surge, coming from the rotating water underneath the hurricane, was generated mainly under the asymmetrical RMW on the right side of the northward path. In addition, Katrina's winds had greatly attenuated on the western side of the storm; prior to landfall, the eyewall was even open to the southwest. Due to both that, the counterclockwise direction of the winds, and the geography of the coastline, it was the areas to the east and north of the landfall path that suffered the extreme storm surge.