Levees 'cannot save New Orleans'; BBC

[Hybridstorm_November2001]

Says National Academy of Engineering (NAE) study:

http://news.bbc.co.uk/2/hi/americas/8017837.stm

[Plant grower]

And I agree 100%.

[HurricaneRobert]

The levees needed repair and reinforcement, which is something we've known for a while, so I wouldn't characterize that as "undue optimism."

Hurricane Katrina was the deadliest storm in US history, causing billions of dollar of damage and leaving tens of thousands of people homeless.

Uh, Galveston?

[Dionne]

Am I the only person that remembers the ominous warning the day before Katrina landfall? We all knew what was coming. The only real surprise was the extent of damage 60 miles inland.

Tracts of land that flooded when the levees failed have been abandoned. Just fly out of NOLA sometime and look down.....it's pretty obvious. BFE's (basic flood elevations) have been changed.

I think we're on target. There is only so much we can do. We could backfill MRGO......but then there is still Ponchartrain on the north.

[somethingfunny]

The levees needed repair and reinforcement, which is something we've known for a while, so I wouldn't characterize that as "undue optimism."

Hurricane Katrina was the deadliest storm in US history, causing billions of dollar of damage and leaving tens of thousands of people homeless.

Uh, Galveston?

I was going to make a snide comment about the BBC not being as good as they say they are, but if you go to the link they already fixed that to say "Hurricane Katrina was one of the deadliest storms in US history, causing...."

Dang. Those British really are good. I wonder if hurricane preparations would be more orderly if we had a station like the BBC over here instead of our sorry excuses for "information entertainment" trying to out-hype one another. (For instance, compare a BBC article and a CNN article on the current swine flu outbreak)

Sorry about derailing the topic.

Isn't the current levee system merely repaired to the same level as the one they had before Katrina? The article is a nice reminder, but it's nothing new....the repaired levees are still the old levees....built to withstand a standard Category 3 hurricane, nothing more.

[jinftl]

Just as tough earthquake building standards are in place in California...after the prior building methods failed during big quakes, there is a duty owed to all residents in New Orleans to make the levees as storm resistent as possible. I know there are financial considerations, but levees should be built to Cat 5 level.

Even then, there is no guarantee. Mother Nature is calling the shots. Humans have always lived in areas prone to natural disasters of one form or another....New Orleans is not alone and should not be dismissed as not worth protecting. Let local, state, and federal officals keep the city safe; let the residents keep themselves safe when a storm threatens by heeding evacuation orders.

By the way, I have seen disaster programs on what would happen if the Thames breakwater defense walls failed if a large sure can in from the North Sea due to a storm system (non-tropical). London would be at risk for major flooding in this worst case scenario. It is always easy when folks (both here in the U.S. and abroad) judge how an area has responded to a disaster when they haven't had to deal with it. It is easy to pat yourself on the back when you haven't 'been there'.

[RL3AO]

Its been changed now.

Hurricane Katrina was one of the deadliest storms in US history, causing billions of dollar of damage and leaving tens of thousands of people homeless.

[Derek Ortt]

The levees needed repair and reinforcement, which is something we've known for a while, so I wouldn't characterize that as "undue optimism."

Hurricane Katrina was the deadliest storm in US history, causing billions of dollar of damage and leaving tens of thousands of people homeless.

Uh, Galveston?

I was going to make a snide comment about the BBC not being as good as they say they are, but if you go to the link they already fixed that to say "Hurricane Katrina was one of the deadliest storms in US history, causing...."

Dang. Those British really are good. I wonder if hurricane preparations would be more orderly if we had a station like the BBC over here instead of our sorry excuses for "information entertainment" trying to out-hype one another. (For instance, compare a BBC article and a CNN article on the current swine flu outbreak)

Sorry about derailing the topic.

Isn't the current levee system merely repaired to the same level as the one they had before Katrina? The article is a nice reminder, but it's nothing new....the repaired levees are still the old levees....built to withstand a standard Category 3 hurricane, nothing more.

and had the levees been built to withstand a cat 3 (which saying they are built to withstand a cat 3 is beyond idiotic as the surge range from a cat 3 is anywhere from 10 to 30 feet in the area), the levees would have held since Katrina was a collapsing cat 3 at landfall

[somethingfunny]

That's why I said "standard" Cat 3. Surge would be "9-12 feet" (although I'm not sure where they ever got that standard in the first place unless they base all their surge projections on the East Coast of Florida)

[jinftl]

Good point...yet another instance where using storm category is flawed....rather than using a derived category as the basis, the levees should be built to withstand a surge of "X feet"....take the highest surge an area has seen and add 5' to it, for example.

Category 5 storm surge protection means very very different things in New Orleans and the upper Gulf Coast than it does in Miami. Such a surge could go 20+ miles inland on the Gulf Coast vs. covering the barrier islands and maybe a few miles inland (at most) in Miami. It's not a total 'get out of jail free card' for Miami though....the city would be much more prone to damaging wave action for the same reasons (slope of coast, depth of water).

The NHC absolutely forecasts surge with specific ranges of height....the question is are people and the media focusing on that...or fixating on storm category?

[Derek Ortt]

no better way to highlight how clownish saying cat 3 surge is than to take 2 very similar cat 3s... Jeanne and Katrina

One produced 6 feet of surge, the other about 28 feet

[wxman57]

That's why I said "standard" Cat 3. Surge would be "9-12 feet" (although I'm not sure where they ever got that standard in the first place unless they base all their surge projections on the East Coast of Florida)

Saffir-Simpson is only a wind scale. Surge is not a function of peak wind in a hurricane. So there's no such thing as a "Cat 3 storm surge". As Derek mentioned, a Cat 3 hitting New Orleans could produce a surge anywhere from a few feet to over 30 feet. The greatest contributor to surge height would be the size of the hurricane force wind field. The greater the radius of max wind and size of the hurricane the larger the surge. Next in line would be the shoaling factor. Shallow water offshore enhances surge. The Louisiana coast has the highest shoaling factor of any location along the U.S. Coast, about 1.8. This shoaling factor is a multiplier for storm surge.

I made a graphic to visualize the shoaling factor surge multiplier years back. Here it is:

[Derek Ortt]

do you have one of those graphics for the EC?

[wxman57]

do you have one of those graphics for the EC?

Don't have the data here, Derek. It's from the U.S. Navy's Shore Protection Manual in the section on how to manually calculate storm surge. The book is on my desk at the office. I typed the data for the Gulf coast into Excel to make the graphic. Hadn't done the east coast yet.

[MGC]

Back when the SS scale was first introduced, there was a corresponding surge and central pressure attached to each category besides sustained winds. 99% of the general public here on the coast still related surge and category. This is why so many lost their lives here on the coast. People were conditioned to accept surge and SS category. Everyone knew the scope of flooding Camille produced as a Cat-5. Many were duped into thinking that since Katrina was weakening Sunday afternoon going into Monday morning that since their property didn't flood during Camille then they would be safe for Katrina. Among them was my spouse's cousin. The family owns a beautiful piece of property on a bluff on a bayou off Bay St. Louis. The property didn't flood during Camille and they incorrectly assumed they would be safe for Katrina. About 10am Monday morning I recieved a call from her saying the water was coming into the house and they were headed to the attic. She also wanted to know where the eye of Katrina was. I told her is was coming ashore in Hancock county, the entire county. A short while later, she calls back saying the water in now inches from getting into the attic and tells me what to do with their bodies in the event they were to die. She and many never expected the surge because Katrina was not a Cat-5. The NHC along with local media must stress the surge and not the sustained winds. A whole heck of a lot of people have died in hurricane surges the past few years while few have died because of the wind. We are rating hurricanes on the wrong storm element.......MGC

[jinftl]

I wholeheartedly agree that the public storm psyche needs to move away from the SS scale...esp in regards to areas of known surge threat. I really can't find any way to blame the NHC for downplaying surge threat and focusing solely on wind damage potential.

The day before landfall, the 4pm CDT advisory specifically stated

COASTAL STORM SURGE FLOODING OF 18 TO 22 FEET ABOVE NORMAL TIDE
LEVELS...LOCALLY AS HIGH AS 28 FEET...ALONG WITH LARGE AND DANGEROUS
BATTERING WAVES...CAN BE EXPECTED NEAR AND TO THE EAST OF WHERE THE
CENTER MAKES LANDFALL. SOME LEVEES IN THE GREATER NEW ORLEANS AREA
COULD BE OVERTOPPED. SIGNIFICANT STORM SURGE FLOODING WILL OCCUR
ELSEWHERE ALONG THE CENTRAL AND NORTHEASTERN GULF OF MEXICO COAST.

Now with a predicted landfall in s.e. louisiana or mississippi, how could any one who read that be unclear?

The info is out there....what is happening is that alot of misinformation (largely based on past storm experiences) makes the rounds alot quicker and carries more weight when being given to us by a friend, family member, etc than it would be by reading or listening to the NHC advisories. Alot of it is 'wives tales' of hurricanes so-to-speak....for example, that only a Cat 5 would flood a particular area and if they didn't flood in Camille, then Katrina is not that big of deal. There is no way anyone who is getting their info from the official sources...and following through with the messages given...could dismiss the threat.

What needs to stop happening...and i would think it would be easier with the recent memories of storms like Katrina at play....is for folks to hear the advisories and forecasts and then 'self-edit' them to fit their experience and understanding of storms.

The type of storm that concerns me the most in some respects is a 'non-major' that threatens with a forecast surge of 15-20 feet...like ike....people will run from a Cat 5...will they run from a Cat 2 with a 20' surge? Will people focus on the Cat 2 part (which really is more reflective of winds) and discount the 20' surge message? Will they make their decision to stay based on factors having nothing to do with the storm at hand....i.e., folklore and past experiences...even though officials are urging them to leave given the surge threat? If there are survivors left in the worst hit area who did not leave, they would be an invaluable source of information into the psyche and storm threats.

Back when the SS scale was first introduced, there was a corresponding surge and central pressure attached to each category besides sustained winds. 99% of the general public here on the coast still related surge and category. This is why so many lost their lives here on the coast. People were conditioned to accept surge and SS category. Everyone knew the scope of flooding Camille produced as a Cat-5. Many were duped into thinking that since Katrina was weakening Sunday afternoon going into Monday morning that since their property didn't flood during Camille then they would be safe for Katrina. Among them was my spouse's cousin. The family owns a beautiful piece of property on a bluff on a bayou off Bay St. Louis. The property didn't flood during Camille and they incorrectly assumed they would be safe for Katrina. About 10am Monday morning I recieved a call from her saying the water was coming into the house and they were headed to the attic. She also wanted to know where the eye of Katrina was. I told her is was coming ashore in Hancock county, the entire county. A short while later, she calls back saying the water in now inches from getting into the attic and tells me what to do with their bodies in the event they were to die. She and many never expected the surge because Katrina was not a Cat-5. The NHC along with local media must stress the surge and not the sustained winds. A whole heck of a lot of people have died in hurricane surges the past few years while few have died because of the wind. We are rating hurricanes on the wrong storm element.......MGC

[MGC]

Well, for whatever reason many did dismiss the warning and elected to stay. Many payed with their lives. I just hope that the surge potential can be better communicated. I shutter at the though of an Ike type system hitting New York or another 1928 hurricane that floods Miami Beach.....MGC

[Ptarmigan]

I think this whole SS Category system is giving people a false sense of security. For example, Ike was Category 2 and yet it produced storm surge as high as 25 feet. Alicia was a Category 3 and produced storm surge of 10 to 15 feet. It is all about the size that causes the storm surge. Ike was large, while Alicia was medium size. If Hurricane Wilma was at its record peak and the area where Katrina or Ike hit, the storm surge would be lower than that of Katrina or Ike. As for why New Orleans flooded, Katrina was a large hurricane and New Orleans got 70 to 100 mph winds, yet they got storm surge of 12 to 16 feet and they ended up being flooded. This is largely due to the floodwalls and levees being poorly maintained and built.

[jinftl]

Agree....i can only hope that one positive consequence of the last few years is that so many people have become more storm savy than ever. People need to listen to the evacuation orders and forecast surge heights...and act accordingly. Every storm is different and if officials say go....go!

Don't want to totally discount the effect of wind....although i do agree it is surge that generally kills and destroys the most. There are noteable and graphic exceptions to that....just think the photos out of Homestead of block after block of destroyed homes from Andrew. A quarter million people....comprising 100,000+ homes....were made homeless from wind damage. Not blue roof cases or lost tiles...we're talking homeless.

Well, for whatever reason many did dismiss the warning and elected to stay. Many payed with their lives. I just hope that the surge potential can be better communicated. I shutter at the though of an Ike type system hitting New York or another 1928 hurricane that floods Miami Beach.....MGC

[Derek Ortt]

Well, for whatever reason many did dismiss the warning and elected to stay. Many payed with their lives. I just hope that the surge potential can be better communicated. I shutter at the though of an Ike type system hitting New York or another 1928 hurricane that floods Miami Beach.....MGC

In the 1926 hurricane that struck Miami (1928 hit Palm Beach and Lake Okeechobee... another ticking time bomb that was probably half a category from going off during Wilma (SS category would have mattered there since the Lake is very small and shallow)) most people did not die from the surge (which was only about 10 feet on Miami Beach (of course higher on the mainland). most died as they tried to evacuate Miami Beach DURING THE EYE. They didn't make it across the bridge in time