Hell and high water – part 2

Katrina was hell and Sop’s story of his trip to hell and back gave our resident construction-specialized CPA the PhD in storm surge evident in his post yesterday and comments this morning.

Storm surge was not something one sees growing up in the tornado alley that cuts across north Mississippi. Judge Senter, I’ve noted, also comes from that part of the State – accounting in some part, no doubt, for his clear understanding of the damage wind alone can do.

surge_small21No one has to grow up in a coastal area to understand storm surge..

Storm surge is simply water that is pushed toward the shore by the force of the winds swirling around the storm. This advancing surge combines with the normal tides to create the hurricane storm tide, which can increase the mean water level 15 feet or more. In addition, wind driven waves are superimposed on the storm tide. This rise in water level can cause severe flooding in coastal areas, particularly when the storm tide coincides with the normal high tides. Because much of the United States’ densely populated Atlantic and Gulf Coast coastlines lie less than 10 feet above mean sea level, the danger from storm tides is tremendous.

However, IMO, there is a distinct difference in the common use of the words storm surge and the description and graphic from the National Hurricane Center – a distinction, simply stated, in water pushed toward the shore and the often resulting flooding. The distinction is “wind driven waves” and the lack of same as water goes inland.

mac-house-location-v21
Red star indicates the location of McIntosh property. The Gulf of Mexico is further south of the tan line marking the location of Popps Ferry Road.

Wind driven waves deliver a power punch as the water comes on shore; but, as Sop has explained to me off-blog, as the water goes inland “think of filling a bathtub”.¬† The McIntosh property was four miles inland, reportedly, and more if you drive from the Beau Rivage, the start-point of my effort to locate the property on a map.

With water on both sides, the area experienced stronger wind than it would have had otherwise; but, not the wave action that caused the destruction at the shoreline.

The property took on rain water as the wind created openings in the structure hours before enough water from the surge had flowed inland to the level of flooding required to enter the structure.

Two videos  found on You Tube are helping in understanding the difference between wind driven surge water and the rising water of flooding.

[vodpod id=ExternalVideo.807844&w=425&h=350&fv=%26rel%3D0%26border%3D0%26]

more about “Hurricane Katrina Video 28 Foot Storm…“, posted with vodpod

[vodpod id=ExternalVideo.807847&w=425&h=350&fv=%26rel%3D0%26border%3D0%26]

more about “Hurricane Katrina DURING the storm Bi…“, posted with vodpod

3 thoughts on “Hell and high water – part 2”

  1. The first vid has embedding disabled but this is the link:
    http://www.youtube.com/watch?v=gd8WiiXNxho

    The surge at the first location was 25 feet (not the 28 claimed in the description). By way of contrast the surge in the back bay area of Biloxi was between 18 and 19 feet which accounts for the survival of the structures (for the most part) in the neighborhood where the McIntosh family lives. I understand there was around 4 feet of water inside the McIntosh residence when the flooding hit that area, I’m guessing somewhere between 9 and 10Am that morning

    Great post.

    sop

  2. About the closest thing to a MS Gulf Coast scenario we had here in LA occurred mostly in Plaquemines Parish.

    Understand many of the homes in Plaquemines Parish were inside levees that ranged from 13 to 17 feet high. Of course many the levees in Plaquemines were not breached but overtopped. The distinction is critically important because the levees resulted in an increase in the the time needed for storm surge flooding to occur. You had hurricane winds hitting homes in Plaquemines for up to 5 hours before any flooding occurred.

    I point this out because insurance companies like State Farm denied the claims in Plaquemines just like the ones on the MS Gulf Coast where there were no levees.

  3. Here is a very simple way to compare the Gulf surge near the beach with the less severe flooding at the northwest corner of Biloxi Bay:
    Compare the total destruction of the Bay-Pass Bridge and the Biloxi-Ocean Springs bridges on Highway 90 to the relatively minor damage to Popps Ferry Bridge in Biloxi Bay. The main damage to Popps Ferry Bridge was from breakaway boats hitting it and sinking under it.

    The McIntosh home and dozens of others were on the peninsula between Big Lake and the Tchoutacabouffa River, west and north of Popps Ferry Bridge.

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