Llano River Bridge Collapse in Texas 21

[JAE]

Video of the collapse due to high river:

https://www.youtube.com/watch?v=EY45z_vXbSQ

Before:

After:

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[ATSE]

"There is no scientific debate about the issue."
That is not true. How the climate changes, how it is manifested in different areas and in different seasons, the weight of dozens of complex variables... is not well understood in the same way we understand heat transfer or harmonic resonance.
While our knowledge is constantly improving regarding climate, to say that the debate is settled is a political statement, not a scientific one.
Engineers tend to make similar statistical mistakes as non-engineers, in that they:
1) tend to assign higher confidence levels (and smaller error) based on a relatively small amount of currently available data, and
2) more weight is placed on more recent events and anecdotal evidence.
[By the way, weather in my area has been real nice in the last 15 years. That must count for something, right? No earthquakes either.]
Seems like humility is lacking when it comes to complex subjects like climate. In every other area of science and engineering it is good to question and re-examine our assumptions. This is true of climate science as well - from the left and the right. If you are screaming at your computer screen right now, you might not be able to think clearly.
Anyway, back to the original post. Thanks to JAE for making us all think about failure and overconfidence during design.

 

[fel3]

thebard3…

A "100-year event" is an event that has a 0.01 (or 1%) probability of occurring in a given year. It does not mean once in 100 years. The "year" value is simply the reciprocal of the probability (e.g., a 5-year event has a 0.20 or 20% probability of occurring in a given year).

The "year" nomenclature is ostensibly a simplification to better communicate the meaning to people who don't understand probability, but it has lead to a complete misunderstanding of the frequency of events.

==========
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[Spartan5]

"There is no scientific debate about the issue."
That is not true. How the climate changes, how it is manifested in different areas and in different seasons, the weight of dozens of complex variables... is not well understood in the same way we understand heat transfer or harmonic resonance.
While our knowledge is constantly improving regarding climate, to say that the debate is settled is a political statement, not a scientific one.

https://en.wikipedia.org/wiki/Scientific_opinion_on_climate_change#Scientific_consensus

Several studies of the consensus have been undertaken. Among the most-cited is a 2013 study of nearly 12,000 abstracts of peer-reviewed papers on climate science published since 1990, of which just over 4,000 papers expressed an opinion on the cause of recent global warming. Of these, 97% agree, explicitly or implicitly, that global warming is happening and is human-caused. It is "extremely likely" that this warming arises from "... human activities, especially emissions of greenhouse gases ..." in the atmosphere. Natural change alone would have had a slight cooling effect rather than a warming effect.

I am aware of no real scientific debate regarding the following statements:
[ul]
[li]"Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia".[/li]
[li] "Atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years".[/li]
[li] Human influence on the climate system is clear. It is extremely likely (95-100% probability)that human influence was the dominant cause of global warming between 1951-2010.[/li]
[li] "Increasing magnitudes of [global] warming increase the likelihood of severe, pervasive, and irreversible impacts"[/li]
[li] "A first step towards adaptation to future climate change is reducing vulnerability and exposure to present climate variability"[/li]
[li] "The overall risks of climate change impacts can be reduced by limiting the rate and magnitude of climate change"[/li]
[li] Without new policies to mitigate climate change, projections suggest an increase in global mean temperature in 2100 of 3.7 to 4.8 °C, relative to pre-industrial levels (median values; the range is 2.5 to 7.8 °C including climate uncertainty).[/li]
[li] The current trajectory of global greenhouse gas emissions is not consistent with limiting global warming to below 1.5 or 2 °C, relative to pre-industrial levels.[19] Pledges made as part of the Cancún Agreements are broadly consistent with cost-effective scenarios that give a "likely" chance (66-100% probability) of limiting global warming (in 2100) to below 3 °C, relative to pre-industrial levels.[/li]
[/ul]
No scientific body of national or international standing maintains a formal opinion dissenting from any of these main points. The last national or international scientific body to drop dissent was the American Association of Petroleum Geologists, which in 2007 updated its statement to its current non-committal position; and stated in 2010 that: "Climate change is peripheral at best to our science […] AAPG does not have credibility in that field […] and as a group we have no particular knowledge of global atmospheric geophysics." Some other organizations, primarily those focusing on geology, also hold non-committal positions.

As scientific debate goes, it seems as if those points are "settled." Is there more research to be done? Sure! Will some of the estimates be subject to change? Certainly! But to suggest that there is still viable scientific debate happening regarding the points above is just not grounded in reality.

Considering there hasn't been any evidence to the contrary presented here, I'd be glad to getting back to discussing how these changes will affect our infrastructure and the need to properly assess the associated risks as well.

 

[thebard3]

The "year" nomenclature is ostensibly a simplification to better communicate the meaning to people who don't understand probability, but it has lead to a complete misunderstanding of the frequency of events.

Correct... and based on historical data.

No matter how it's interpreted, it doesn't change the substance of my point. Two 1% probability events in close proximity do not indicate the statistical probability has changed.

Brad Waybright

It's all okay as long as it's okay.

 

[berkshire]

I remember a teacher doing probability when I was in high school using a coin for his lecture. He said " There is a 50 /50 chance of the coin landing heads or tails. BUT THE COIN DOES NOT KNOW THAT."
B.E.

You are judged not by what you know, but by what you can do.

 

[BridgeSmith]

Spartan5, you may dismiss everything that you don't want to take the time to examine as much as you like. You can regurgitate the same old, tired, debunked rhetoric from the climate change alarmists 'til the cows come home, but it doesn't make it true. You can tout the thousands of government-funded studies that found a way to come to the conclusions that got them more government funding, but real science is about what is provable, not about popular opinion or the volume of blather produced.

Any attempt to tie this flooding event to global warming is ridiculous political rhetoric, not worthy of level of discourse that should be expected in a professional forum. If you can't sort out the obvious distinctions between trends in the global climate and regional variations in weather patterns, I find little reason to debate the subject further.

fel3, berkshire, and theBard3, thank you for the explanations of probabilities as it relates to 100-year events, etc. As I was on the road today, I was thinking of a response along the same lines. If you flip a coin 8 times (representing the prediction a 25-year event with 200 years worth of data) and it comes up heads 6 times, that does not mean that the chance of getting heads is 75%. It's a statistical anomaly, primarily attributable to an insufficient sample size.

 

[microwizard]

Climate change denial events are becoming more frequent.

I wonder how much of our infrastructure will be washed away before people accept the truth. That is the real "failure and disaster".

 

[LionelHutz]

I find it hard to buy into the rhetoric that storms are worse today then they have been historically. I try to pay attention to historical data of similar events when a storm occurs. During many of these media touted "worst ever" weather events I see that similar weather events have also occurred 60-200 years ago. For example, Florence really wasn't an abnormal hurricane only possible today. There have been a number of other recorded hurricanes as strong or stronger that have hit that area dating back to the last 200 years.

We have recently built-up many areas more that in the past. So there are more structures and people for these storms to impact. This just makes the impact and devastation of the humans and infrastructure worse then what has occurred historically. But, that impact is often confused with it being a worse storm event.

East Pacific - I believe there have been 2 category 5 hurricanes this year. Apparently 1994 had 3 stronger ones. Just saying...

 

[IRstuff]

from

http://www.stormfax.com/huryear.htm

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[waross]

I note that the Stormfax graph may list only Hurricanes that hit the US.

Original Data is from
The Deadliest, Costliest, and Most Intense United States Hurricanes 1900-2000
[Revised and expanded 2018

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[BridgeSmith]

Nice graph, IRstuff. Interesting how your graph shows an increase in hurricanes, while the oneshere,here, and here at the one I posted earlier, the hurricanes are declining. Ask yourself how the number and strength of hurricanes was determined before the age of weather radar and satellites...

 

[IRstuff]

Oh, I wonder how Beaufort came up with his scale of storm strength in 1805??? Do you suppose he used the wet finger approach? Of course, they adapted the scale for anemometer readings in 1850, given that the anemometer was invented in 15th century.

As for the articles cited, they're comparing apples to oranges, almost literally, since the hurricanes they're talking about are more apropos for latitudes where apples are common fruit, as opposed to tropical hurricanes, where oranges are more common.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[ATSE]

Okay friends, I'll admit my mistake.
What I meant to say is the following.
Engineers tend to make similar statistical mistakes as non-engineers, in that they:
1) tend to assign higher confidence levels (and smaller error) based on a relatively small amount of currently available data, and
2) more weight is placed on more recent events and anecdotal evidence.
3) mix correlation with causation, or get causal arrows flipped.
For my friends who believe themselves to be experts in data analysis, here's a basic question that we should all get about the same answer:
How many data points do you need to predict a future event with 98% certainty that you are within 2% error, assuming no accurate priors?
Then ask yourself how might you aggregate and sort the data from various cities across the last, say 300 years? Clearly we can draw a few hundred different curves.
And lastly, ask yourself, why is it that the vast majority of individuals that assign extreme weather-related events as a direct result of climate change also have similar political views?
No doubt the climate is changing; can't quantity all the reasons, nor are predictions that I've seen very accurate. But we're just human, and even smart people have biases.
Engineer takeaway: reason is your companion, but the Code is your friend. Let the Code guys and gals define the extreme events.

 

[IRstuff]

"Let the Code guys and gals define the extreme events."

And how are they different from the engineers that tend to make similar statistical mistakes as non-engineers?

The news had quite a bit about how South Florida's building codes got washed down from what they should have been.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[zeusfaber]

And lastly, ask yourself, why is it that the vast majority of individuals that assign extreme weather-related events as a direct result of climate change also have similar political views?

I wonder if that's a statement born of a North American experience of the debate?

Engineers tend to ... mix correlation with causation, or get causal arrows flipped

An observation worth bearing in mind while doing the "asking yourself" recommended in the first quote.

(Rats. I'd promised myself I wouldn't get embroiled in this spat).

A.

 

[JAE]

(Rats. I'd promised myself I wouldn't get embroiled in this spat).

I quit after my original first post!


Check out Eng-Tips Forum's Policies here:
faq731-376

 

[Spartan5]

ATSE, I think one of the biggest mistakes that engineers tend to make is to not stay in our lanes. That's in part why I think it is explicit in our code and regulations that we are only to practice in the areas that we are proficient. It is inherent in engineers to have confidence in what we think we know. So we think that because we took a 200 level class in statistics, we can profess to have sufficient knowledge to offhandedly dismiss a comprehensive peer reviewed work having a clear and detailed methodology (NOAA Atlas 14 in this instance).

It is what allows people to dismiss the actual honest to god science as "old, tired, debunked rhetoric" that's not provable. That's the same argument that one of my PE "mentors" made about evolution. "Prove it!" Haha, right? For some people, maybe not haha. Creationism is something which was revealed to them and they choose to believe rather than to accept the science. This mentor was a special kind of creationist who believed that the planet was only 6,000 years old. When faced with the reality that it was billions of years old, the response was the same. "Prove it!" Carbon dating? Flawed. The geologic record? Misinterpreted. The statistics that supported it all? Contrived. I kid you not... when mentioning plate tectonics in a discussion about an earthquake this person responded, "plate tectonics is just a theory." I guess the main thing he taught me was that you don't have to be smart to be an engineer.

What's the point of all of that? Acceptance vs. Belief. Discovery vs. Revelation. When I see that no scientific body of national or international standing maintains a formal opinion dissenting from of the main points regarding climate change that I posted above, I accept that science. Likewise evolution. Likewise the age of the planet. Likewise plate tectonics even. The science is what the science is. As such, I'm going to stay in my lane. Alternatively, in the case of climate change, I can accept what is revealed to me by Exxon Mobil and the petrochemical geologists and political hacks and everyone else who has a vested interest in the status quo that got us here.

It's remarkable that this discussion regarding precipitation intensity took the same tack as the climate change debate writ large. The first approach to dismissing the science was outright denial that the climate was changing ("The problem is that the evidence doesn't actually support that assumption."). When it became clear that it was indeed changing, then it transitioned to obfuscation; i.e. "So, perhaps the rainfall patterns in Texas are changing. It's always been changing. This is all completely normal." And it's interesting to me how the statement that set all of this off "This type of storm, and the hurricanes, continue to get more frequent and more severe." made no mention whatsoever to the climate change debate. It was injected by someone who wanted to argue against it and take the opportunity to make wholly unsupported claims that it was (to paraphrase) "debunked fear-mongering rhetoric."

 

[BridgeSmith]

"Oh, I wonder how Beaufort came up with his scale of storm strength in 1805???"

I wasn't talking about the strength scale; I was referring to the lack of tools available to accurately measure the strength of the hurricanes that did occur during those earlier years.

"...since the hurricanes they're talking about are more apropos for latitudes where apples are common fruit, as opposed to tropical hurricanes, where oranges are more common."

When did I assert that my statement only applied to tropical hurricanes? For that matter, when did you?

 

[BridgeSmith]

"The first approach to dismissing the science was outright denial that the climate was changing ("The problem is that the evidence doesn't actually support that assumption.")."

Perhaps you should have looked more closely at the statement I was responding to, before making incorrect assumptions about it. My response was to the statement "This type of storm, and the hurricanes, continue to get more frequent and more severe." Over hundreds and thousands of years, regional and global climates experience change. There is much evidence that this does indeed occur, and I would not attempt to dispute that. However, the evidence does not support the contention that there is really a regional or global change in the number or severity of hurricanes or other storms.

BTW, using double quotes, which denotes a direct quote of someone, and then inserting your own (incorrect) interpretation of what the person said, is bad form, and a sure sign of desperation.

 

[Spartan5]

Perhaps you should have looked more closely at the statement I was responding to, before making incorrect assumptions about it. My response was to the statement "This type of storm, and the hurricanes, continue to get more frequent and more severe." Over hundreds and thousands of years, regional and global climates experience change. There is much evidence that this does indeed occur, and I would not attempt to dispute that. However, the evidence does not support the contention that there is really a regional or global change in the number or severity of hurricanes or other storms.

There is evidence of a regional change in the intensity of storms. I posted it. You acknowledged it (twice; "So, perhaps the rainfall patterns in Texas are changing." "Regional rainfall patterns change."). You seem like you might be disoriented by some cognitive dissonance you experiencing.

Even in your post above, you say there is evidence of change... then the very next sentence you say the evidence doesn't support that there is a change.

So out of one side of your mouth you're saying there is always change (dismissing/diminishing it), and the other you say there is no evidence of change (denying it). Which is it?