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Llano River Bridge Collapse in Texas
21

Llano River Bridge Collapse in Texas

RE: Llano River Bridge Collapse in Texas

Incredible video. Not an engineering failure, per se. I'm fairly sure it wasn't designed to withstand that level of flooding.

RE: Llano River Bridge Collapse in Texas

...I thought in the forum title "engineering" applied to both "failures" and "disasters". Oh well, it still makes for some great video footage.

RE: Llano River Bridge Collapse in Texas

That's just incredible to see the bridge structure and concrete slabs "flowing" downstream. Doesn't look like a lot of clearance under the bridge in the top picture so maybe a failure in planning? Wouldn't have cost much to raise it up 5 feet.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Llano River Bridge Collapse in Texas

Washington Post reports this was the highest water level recorded there in 83 years. I am unable to determine when the bridge was built, but was probably designed to withstand a 100 year event.

Brad Waybright

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

RE: Llano River Bridge Collapse in Texas

100 year storms now are not what they were 83 years ago... Computer models are always changing as more data enters the system.

Mike McCann, PE, SE (WA)


RE: Llano River Bridge Collapse in Texas

"Wouldn't have cost much to raise it up 5 feet."

How about 10 feet? Where do you draw the line? Most likely, it was adequate for a 500 year flood event. Depending on the foundation conditions, that extra 5 feet could cost quite a bit.

It also may not be as simple as just raising the bridge portion. What made the Sunshine Skyway bridge collapse much worse is that the bridge profile grade was on a crest, so drivers could not see that a span had collapsed in time to avoid driving off into the river.

RE: Llano River Bridge Collapse in Texas

It was reported that the Llano River had risen 35 feet prior to the bridge failing. I suspect that that went well beyond what engineers would have considered to have been a "100 year event".

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Llano River Bridge Collapse in Texas

The video seems to show the upstream side falling, so it's more likely that the footings got eroded, rather that the bridge deck getting pushed off it supports. That would suggest that the height was irrelevant; it was simply the shear volume and speed of water running over the footings.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Llano River Bridge Collapse in Texas

I suppose all buildings along the Gulf Coast could be designed to withstand a Cat. 5 hurricane, too. At what point does spending an extra X% to protect a structure from an extremely unlikely event become an unjustified expense? When safeguarding lives is involved, quite a bit of extra expense is justified (not the case here, as there was plenty of time to close the bridge before collapse). When essential services would be interrupted, there is also justification to spend some extra cash to lessen the likelihood of failure. That may or may not be the case here; I don't know what other access routes are available, nor what level of event the bridge was designed for or had freeboard for.

RE: Llano River Bridge Collapse in Texas

There is a point here that might be missed, but would the essential services people have to assume the reliability of the bridge, and it might be expected they might assume wrong?

RE: Llano River Bridge Collapse in Texas

There are categories for essential and critical bridges that require design for more extreme events. I don't have any information on whether that particular bridge qualifies for either of those categories, or what level of event this flood may have been.

RE: Llano River Bridge Collapse in Texas

Well, I assume it will take at least two years to replace this bridge, not considering arguing about paying for it.

How much is the lack of usage going to cost the local economy?

Mike McCann, PE, SE (WA)


RE: Llano River Bridge Collapse in Texas

I've grown up in this area. I've hunted and fished in this area in the 1960s-1980s. This area and the surrounding Austin metro area has grown over the past 50 years. I doubt the designers realized the amount of impervious cover that was going to be created in the Austin and Hill Country region.

RE: Llano River Bridge Collapse in Texas

"At what point does spending an extra X% to protect a structure from an extremely unlikely event become an unjustified expense?"

That supposes that this latest hurricane was "an extremely unlikely" event. One issue that the likelihood statistic is only based on the last 200 years or so. Another is that it's well known that the requirements have invariably gotten watered down because of the gnashing of teeth at the cost to implement designs for the actual extreme requirements.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Llano River Bridge Collapse in Texas

It appears that some people here is under the impression that the flooding in the Llano, Texas area was somehow related to Hurricane Micheal. I was not aware that it had moved from Georgia and the Carolina's to Texas. My understanding was that while Michael was a near-category 5 hurricane, that it is was very compact and fast moving so I'm not sure how much of an impact it had on a location hundreds of miles from the Florida pan-handle.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Llano River Bridge Collapse in Texas

"That supposes that this latest hurricane was 'an extremely unlikely' event."

Not necessarily. I was attempting to shed some light, in general terms, on the decision-making process used to set the design criteria for civil infrastructure. I haven't seem anything thus far indicating how the level of flooding in this instance would be classified. Nor have I seen what level of flooding event the bridge was designed for. Without those two pieces of information, it's impossible to say whether this was a design failure, the result of inadequate design criteria, or an extremely unlikely event which was not reasonable to anticipate, nor spend hundreds of thousands or millions of dollars to mitigate a tiny risk.

In hindsight, it's easy to say they should have spent the money, since it will now cost millions more to replace it. However, spending an extra million or so, of a finite budget, to potentially save this bridge from an event it isn't likely to ever see within its useful life, would have meant other bridges didn't get safety upgrades that could save lives. Maintaining infrastructure on a limited budget requires tradeoffs and making hard decisions about how to allocate resources. It must be done prudently, weighing risk against cost, and placing a high premium on the safety of those using that infrastructure.

RE: Llano River Bridge Collapse in Texas

While it wasn't a hurricane, it was a boatload of rain; totaling 4 to 8 inches over 4 days, equivalent to the rainfall for a entire normal October. The net result was the Llano river level rising 37 ft in less than 2 days.

This type of storm, and the hurricanes, continue to get more frequent and more severe.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Llano River Bridge Collapse in Texas

"This type of storm, and the hurricanes, continue to get more frequent and more severe."

Yeah, I heard the same fear-mongering from the IPCC, too. The problem is that the evidence doesn't actually support that assumption.

RE: Llano River Bridge Collapse in Texas

"4 to 8 inches over 4 days" consists of a series of light showers where I am. We just had that, and it helped to turn the grass green, but certainly no flooding. Must have been more than that, or the topography is really strange.

RE: Llano River Bridge Collapse in Texas

That depends on the how the runoff gets to the river. The end result was 37 ft river rise in about a day, which could certainly be due to poor ground absorption. 1-inch rain in a short time in parts of Los Angeles would result in flooded streets.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Llano River Bridge Collapse in Texas

It all depends on what's normal for the area. Apparently, 4-8" is a typical monthly total for that area. Here, 4" would be nearly 6 months worth of rain, and 8" close to our yearly average. Needless to say, 2" of rain at one time causes major flooding. It all depends on the capacity of the river channel and the drainage area. That said, major flooding from a typical monthly rainfall amount in 4 days, did seem odd, so I looked at the monthly averages for Austin. There are a few months where the monthly average precipitation tops 4", but the highest is 4.37" in May, following the driest 6 months of the year. October is toward the end of the 'wet season', and it's not just the 4-8" in the 4 days, it's whether the ground was already saturated when that heavy rain fell.

RE: Llano River Bridge Collapse in Texas

In Orange Co (CA), the official rainfall for the year (Oct 2017 to Oct 2018) was less than 1.8 inches (the historical normal is closer to 13 inches). Now we appear to be starting out on a better note this season as we had a thunderstorm on Saturday that dropped 0.4 inches of rain in 24 hours (no reported flooding). It's also been reported that we will have an El Niño condition in the Pacific this winter which could mean a wetter than normal rainy season. We can only hope...

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Llano River Bridge Collapse in Texas

John,
Sorry to be a contrarian, and I do hope you get some rain, but an El Nino means less rain for Australia, and we need it. We like the La Nina condition better.

RE: Llano River Bridge Collapse in Texas

Quote (msquared48)

100 year storms now are not what they were 83 years ago... Computer models are always changing as more data enters the system.

https://www.noaa.gov/media-release/noaa-updates-te...

Quote:

A NOAA analysis released today finds significantly higher rainfall frequency values in parts of Texas, redefining the amount of rainfall it takes to qualify as a 100-year or 1000-year event.

The study, published as NOAA Atlas 14, Volume 11 Precipitation-Frequency Atlas of the United States, Texas, found increased values in parts of Texas, including larger cities such as Austin and Houston, that will result in changes to the rainfall amounts that define 100-year events, which are those that on average occur every 100 years or have a one percent chance of happening in any given year. In Austin, for example, 100-year rainfall amounts for 24 hours increased as much as three inches up to 13 inches. 100-year estimates around Houston increased from 13 inches to 18 inches and values previously classified as 100-year events are now much more frequent 25-year events.

NOAA Atlas 14 rainfall values are used for infrastructure design and planning activities under federal, state and local regulations. They also help delineate flood risks, manage development in floodplains for FEMA’s National Flood Insurance Program and are used to monitor precipitation observations and forecasts that can indicate flooding threats by NOAA’s National Weather Service.

RE: Llano River Bridge Collapse in Texas



Quote:

38 Robinson City Park in Llano will flood. Many homes in Scotts Acres on south side of Llano will be severely damaged and lowest mobile homes destroyed in water up to 6 feet, some washing downstream. Many homes near Castell to below Llano will be damaged. The FM 2900 bridge in Kingsland will flood. Much of Kingsland Lodge in Kingsland will be destroyed. Many homes downstream in Marble Falls will flood as flow backs up Backbone Creek.

36 Disastrous life threatening flooding will damage numerous homes and businesses above Castell to Lake LBJ. Numerous resorts at and below Kingsland near the Llano River mouth will flood severely. Boats, docks and any gear that isn't removed from the river will be destroyed. Lower homes on Lake Travis flood severely. Flow exceeds the USGS 1:50 year flood level.

32 Disastrous flooding well into the flood plain will cut off and potentially drown thousands of livestock. Homes, resorts, commercial buildings, boats, docks and marinas will flood disastrously above Castell to Marble Falls on Lake LBJ. Roads and bridges near the river will be severely flooded and dangerous to motorists. Exceeds the USGS 1:25 year flood.

30 Disastrous flooding will reach lowest residences below Castell to below Llano. Flow will be to the slab of the city of Llano water treatment plant on the right bank just above Highway 16. Numerous resorts at Kingsland and in Lake LBJ will have severe flood damage. Boats, docks and facilities lining the lower Llano and Lake LBJ near Kingsland may be severely damaged or destroyed.

26 Major flooding will threaten lowest homes from upstream near Castell to below Llano. Major damage will occur downsteam in Kingsland to boats and docks. Secondary and primary roads and bridges in the flood plain will be extremely dangerous to motorists. Lowest homes and businesses in the Highland Lakes below Kingsland will be flooded.

23 Major lowland flooding makes primary and secondary roads and low bridges near the river and tributaries dangerous. Boats and docks are severely inundated downstream near and in Kingsland. Lowest resorts near the Llano River mouth in Kingsland flood.

20 Flow will be damaging to docks and boats downstream in Kingsland. The lowest secondary roads and bridges will be severely flooded and dangerous. Near the USGS 1:5 year flood level.

16 Moderate lowland flooding threatens docks and boats in the flood plain downstream in Kingsland. Secondary roads and bridges will be flooded and dangerous to motorists. Flow exceeds the USGS 1:2 year flood level.

12 Moderate lowland flooding makes secondary roads and low bridges in the flood plain dangerous to motorists. Equipment should be moved from low docks and boat ties loosened downstream in Kingsland.

10 Minor lowland flooding can swamp boats in the lower Llano River in Kingsland.

Quote:

Historic Crests
(1) 41.50 ft on 06/14/1935
(2) 39.10 ft on 06/23/1997
(3) 32.60 ft on 09/10/1952
(4) 28.65 ft on 11/04/2000
(5) 22.07 ft on 11/17/2004
(6) 20.51 ft on 02/04/1992
(7) 20.50 ft on 06/27/2007
(8) 12.63 ft on 06/01/2016
(9) 12.13 ft on 05/29/2015
(10) 11.24 ft on 07/06/2002

https://water.weather.gov/ahps2/hydrograph.php?wfo...

RE: Llano River Bridge Collapse in Texas

Quote (HotRod10)

"This type of storm, and the hurricanes, continue to get more frequent and more severe."

Yeah, I heard the same fear-mongering from the IPCC, too. The problem is that the evidence doesn't actually support that assumption.
It's seems like there is ample evidence that extreme precipitation events are on the increase. Not limited to the specific statistical analysis that's relevant in this case which shows: In Austin, for example, 100-year rainfall amounts for 24 hours increased as much as three inches up to 13 inches. 100-year estimates around Houston increased from 13 inches to 18 inches and values previously classified as 100-year events are now much more frequent 25-year events.

That seems pretty straightforward. What is it we are missing?

RE: Llano River Bridge Collapse in Texas

So, perhaps the rainfall patterns in Texas are changing. If they are, what does it mean?

That the bridge was underdesigned? No, not necessarily. The design would have been based on the information available at the time, and we haven't been presented with what the design criteria was.

That the changes are due to global warming? Assuming that global warming is a real, long term trend, and not a normal cyclic fluctuation (and assuming it's not a completely fabricated phenomenon), it's only wild speculation, with no scientific foundation, that rainfall in Texas would be affected.

Actually, the heavy rainfall that caused this flooding on the Llano River was the result of a Pacific hurricane named Sergio.

RE: Llano River Bridge Collapse in Texas

Quote (Spartan5)

100-year estimates around Houston increased from 13 inches to 18 inches and values previously classified as 100-year events are now much more frequent 25-year events.
Perhaps previous estimates were in error? Please consider this is a question, not a statement.

Brad Waybright

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

RE: Llano River Bridge Collapse in Texas

"What is it we are missing?"

The fact that, as IRstuff pointed out, we only have 200 years worth of data to work with, and only about the last 100 years for which we have actual measurements. To set the criteria for what constitutes a 100-year (or even 25-year) event with any accuracy, you need far more 100 or even 200 years worth of data. Also, statistically speaking, 2 or even 3 "100-year events" can happen within a few years of each other; that doesn't suddenly make them 5-year events.

Anyway, my comment was primarily aimed at the assertion of hurricanes becoming more frequent and more severe, which is not supported by the facts.

RE: Llano River Bridge Collapse in Texas

2

Quote (HotRod10)

So, perhaps the rainfall patterns in Texas are changing. If they are, what does it mean?

It means that you were wrong when you claimed that the statement "This type of storm, and the hurricanes, continue to get more frequent and more severe" was fear-mongering and unsupported by evidence. There's the evidence for you. There is evidence that it's not just Texas. Do you want to read more studies?

Hurricane Sergio, by the way, was the record setting eighth Category 4 hurricane to form in the East Pacific this year. The old record of seven Category 4 having only been set in 2015. All just a strange coincidence I guess.

RE: Llano River Bridge Collapse in Texas

Quote (HotRod10)

To set the criteria for what constitutes a 100-year (or even 25-year) event with any accuracy, you need far more 100 or even 200 years worth of data.
Sez who?

Have you ever cracked open a copy of Atlas 14? The statistical analysis is all there (with confidence intervals) in hundreds of pages of details. It's not like they are licking their finger and sticking it in the wind.

http://www.nws.noaa.gov/oh/hdsc/PF_documents/Atlas...

RE: Llano River Bridge Collapse in Texas

"There is evidence that it's not just Texas. Do you want to read more studies?"

Regional rainfall patterns change. Regional rainfall patterns have changed throughout recorded history. There is historical evidence of changing regional rainfall patterns as far back as you care to go. It's not evidence of anything other than the Earth is constantly changing, as it has since it was created.

"All just a strange coincidence I guess."

Technically, it's a statistical anomoly, but you can buy into the junk science if you choose.

"Sez who?"

My college statistics teacher...and the book he taught from.

RE: Llano River Bridge Collapse in Texas

2
To clarify, there is no scientific body that rejects the fact the that climate change is occurring. There is no scientific debate about the issue. Even the oil companies begrudgingly agree. The moon landing wasn't fake, the earth isn't flat, and climate change isn't a hoax.

RE: Llano River Bridge Collapse in Texas

The climate is always changing, regionally and globally. Of course no credible scientist would deny such an obvious fact. However, a sustained global warming trend is not a fact; it's a hypothesis still in search of supporting evidence. Beyond that, the supposition that a warming climate produces more frequent and severe storms and hurricanes, is speculation not supported by the evidence. There is actually a substantial amount of evidence to the contrary.

RE: Llano River Bridge Collapse in Texas

Quote (HotRod10)

Technically, it's a statistical anomoly, but you can buy into the junk science if you choose.
At first you claimed that talk of changes in extreme precipitation events was fear-mongering not supported by evidence. Then you wavered and said well maybe it's just Texas. Finally there was the hard pivot to "Things change. Things have always changed. There is evidence things have changed as far back as you can go. There is constant change." But I'm the one that has bought into something?

What have I presented that's the junk science you claim I have bought into?

Though I'm not even really sure what your position is at this point, I'm curious; aside from anonymous professors and their unnamed textbooks, do you have anything to contribute from reputable sources (say something not founded by a political hack with no education in the field of climate science)? Substantial amounts of actual science is what I'm specifically looking for here. Climate Depot is a cesspool. Granted, there might be a grain of knowledge there... somewhere... maybe. But I've never been one to dive into a septic tank just because someone might have dropped a gold ring in it.

RE: Llano River Bridge Collapse in Texas

Quote (HotRod10)

Also, statistically speaking, 2 or even 3 "100-year events" can happen within a few years of each other; that doesn't suddenly make them 5-year events.
A 100 year event, by definition, indicates probability to occur in any given location during a 100 year span. Many 100 year events should be expected to occur in various locations during a 100 year span. Since this storm didn't hit Louisiana, and one might hit there next week does not qualify to assert that two 100 year floods within 2 weeks occurred.

Brad Waybright

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

RE: Llano River Bridge Collapse in Texas

You know, it makes me curious when they started using the concept of a 100-year flood. Anybody know when that was? More to the point, did they even use that concept 50 years ago? Or was it a matter of "the water hasn't ever come up this high, so let's put the bridge here".

RE: Llano River Bridge Collapse in Texas

Recurrence intervals on storm events for flood events have been used at least since the 1930's. No idea its use before then, though it wouldnt surprise me if it was used prior to the 1930's. The math of it isnt too complex. I've seen it on historical drawings/projects I've worked on. For wind, seismic events, I think the use of recurrence intervals is a little more recent.

RE: Llano River Bridge Collapse in Texas

3
"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.

RE: Llano River Bridge Collapse in Texas

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

RE: Llano River Bridge Collapse in Texas

Quote (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.

https://en.wikipedia.org/wiki/Scientific_opinion_o...

Quote:

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:
  • "Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia".
  • "Atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years".
  • 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.
  • "Increasing magnitudes of [global] warming increase the likelihood of severe, pervasive, and irreversible impacts"
  • "A first step towards adaptation to future climate change is reducing vulnerability and exposure to present climate variability"
  • "The overall risks of climate change impacts can be reduced by limiting the rate and magnitude of climate change"
  • 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).
  • 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.
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.

RE: Llano River Bridge Collapse in Texas

Quote (fel3)

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.

RE: Llano River Bridge Collapse in Texas

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.

RE: Llano River Bridge Collapse in Texas

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.

RE: Llano River Bridge Collapse in Texas

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".

RE: Llano River Bridge Collapse in Texas

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...

RE: Llano River Bridge Collapse in Texas

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

Quote (STORMFAX)

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

RE: Llano River Bridge Collapse in Texas

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...

RE: Llano River Bridge Collapse in Texas

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)
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RE: Llano River Bridge Collapse in Texas

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.

RE: Llano River Bridge Collapse in Texas

"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)
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RE: Llano River Bridge Collapse in Texas

Quote (ATSE)

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?

Quote (ATSE)

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.

RE: Llano River Bridge Collapse in Texas

(OP)

Quote (zeusfaber)

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

I quit after my original first post! smile

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RE: Llano River Bridge Collapse in Texas

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."

RE: Llano River Bridge Collapse in Texas

"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?

RE: Llano River Bridge Collapse in Texas

"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.

RE: Llano River Bridge Collapse in Texas

Quote (HotRod10)

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?

RE: Llano River Bridge Collapse in Texas

A local curious "statistical anomaly":

RE: Llano River Bridge Collapse in Texas

I said it'spossible rainfall patterns are changing in the region, but it's also possible that the recent heavier rains are just an anomaly, like having a flipped coin come up heads 6 times out of 8.

Someday Spartan5, perhaps you'll grasp the difference between accepting the obvious that change does happen, and accepting the unsupported assertion that a particular change is taking place in a particular region at a particular time. I'm rapidly losing hope, though.

Again, nice graphs, but completely irrelevant.

RE: Llano River Bridge Collapse in Texas

As far as the changes to the rainfall event frequency update by NOAA for the region, there remains the possibly that the historical record simply does not go back far enough to accurately predict the return periods for those events. According to the report in your link, they are "redefining the amount of rainfall it takes to qualify as a 100-year or 1000-year event." Not surprising that they need to redefine them, considering they only have 200 years worth of data to work with (again, only a hundred or so of which is reliable). The change is just as easily the result of an inadequate data set as an actual change in the regional climate (which, of course, I never denied was a possibility, just didn't accept as fact).

RE: Llano River Bridge Collapse in Texas

To circle back somewhat closer to the actual subject, regardless whether the higher rainfall represents an anomaly or shift in the climate, the changes to the NOAA Atlas 14 occurred well after the subject bridge was designed and built. Therefore, it should not be assumed to an inadequate design because it was not adequate for this flood event.

RE: Llano River Bridge Collapse in Texas

Quote (HotRod10)

I said it'spossible rainfall patterns are changing in the region, but it's also possible that the recent heavier rains are just an anomaly, like having a flipped coin come up heads 6 times out of 8.

Someday Spartan5, perhaps you'll grasp the difference between accepting the obvious that change does happen, and accepting the unsupported assertion that a particular change is taking place in a particular region at a particular time. I'm rapidly losing hope, though
HotRod... you're welcome to believe whatever you want. In a world in which anything can be dismissed by boiling it down to a coin toss exercise, some really fascinating things must be possible. I envy the power of your imagination.

I accept the science though. The science that has been supported by detailed and comprehensive statistical analysis conducted by experts in their field, and published for all to validate and comment on.

Are you really trying to tell all of us that what I posted is an unsupported assertion: In Austin, for example, 100-year rainfall amounts for 24 hours increased as much as three inches up to 13 inches. 100-year estimates around Houston increased from 13 inches to 18 inches and values previously classified as 100-year events are now much more frequent 25-year events. Do you really profess to know more about statistics than those who completed that work?

RE: Llano River Bridge Collapse in Texas

"Do you really profess to know more about statistics than those who completed that work?"

I didn't see a claim in that statement that the climate in Austin, Texas has changed, only that the statistical probabilities related to rainfall amounts have been revised based recent data. If 50 years from now, they haven't seen rainfall events as significant as those occurring recently, the probabilities will likely be revised back down. As I tried to explain to you several times, regardless of what the rainfall amounts average out to be, or how those averages get revised in the future, it is not necessarily evidence of a change in the climate. It could very well be due to the historical record being inadequate to accurately establish the probabilities. The sample size is just to small to really know.

RE: Llano River Bridge Collapse in Texas

Quote (HotRod10)

"Prove it."
Like evolution. Or the age of the planet.

I surrender.

RE: Llano River Bridge Collapse in Texas

Nice parting shot, Spartan5. Make up a quote, attribute it to me, and then run away. Very professional.

RE: Llano River Bridge Collapse in Texas

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.

I pointed out that the same basic instrument for the measurement of air speed was invented in 15th century, and the Beaufort system used anemometers for windspeed measurements in 1850, so it's been nearly 170 years of reasonably accurate windspeed measurement.

"...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?"

You referenced a slew of articles, which, I pointed out, are talking about mid-latitude storms, and not tropical storms.

TTFN (ta ta for now)
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RE: Llano River Bridge Collapse in Texas

"I pointed out that the same basic instrument for the measurement of air speed was invented in 15th century..."

Are you really going try to argue that a few anemometers can measure the intensity and size of a hurricane as accurately as a satellite? BTW, does your graph include only the intensity of the hurricanes as they made landfall? I'll bet most or all of the few anemometers that were around in the 1800's were land based.

"You referenced a slew of articles, which, I pointed out, are talking about mid-latitude storms, and not tropical storms."

Ok, fine. Since when is the count of tropical hurricanes more valid in determining the overall trend than mid-latitude hurricanes?

RE: Llano River Bridge Collapse in Texas

Quote (jgailla)


Also known as 'cognitive dissonance'. Nobody wins the argument, they just become more sure of their view.

Brad Waybright

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

RE: Llano River Bridge Collapse in Texas

Really, the biggest problem with the climate change "debate" is exactly this. Climate change has been latched onto as a political vehicle, with a good chance of leveraging it for cash (see: carbon trading, for example).
Now, it's practically become a cult religion. The members point to all the papers printed agreeing with them, because nobody dares to disagree anymore. They get shouted down and driven away, from what I've seen. Anyone who dares to even ask what happened to the disastrous climate events predicted in the past, that we're supposed to be suffering from now, gets the same treatment.
Personally, I feel we do need to clean up our act - but not because of whether or not the climate might change. Just because of general pollution levels, less crap in the air, water, and land, and less waste. It seems like the responsible and efficient thing to do in any case.
Perhaps instead of threatening people with hell, we should be working on improving society and education so that they will willingly work towards a better future?

RE: Llano River Bridge Collapse in Texas

Here is the statement from the World Meteorological Organization on climate change and tropical cyclones. Before anyone reads the statement and calls this a flip flop or a capitulation, let's remind ourselves of the original statement made by IRstuff that I took issue with: "This type of storm, and the hurricanes, continue to get more frequent and more severe."

Now let's see what the first point of the WMO statement says about that: "1. Though there is evidence both for and against the existence of a detectable anthropogenic signal in the tropical cyclone climate record to date, no firm conclusion can be made on this point."

RE: Llano River Bridge Collapse in Texas

I wonder what other scientific phenomenon/discoveries had similar turmoil in history or if they would've if information/disinformatoin was so rapidly shared then. Galileo is probably the easiest example to point to. I wonder if people claimed Ampere and Faraday were full of it.

It'd sure be a shame if we spent all this time and effort to try to reduce pollution and human waste for nothing. Maybe after another 100 years of data the "debate" will finally be settled. Based off the ongoing arguments against evolution it doesn't seem likely.

RE: Llano River Bridge Collapse in Texas

Don't worry, RVAmeche, when the effects of the solar minimum are fully felt, the global warming alarmists will once again become global cooling alarmists, though the solution will be the same - more power and money to the government.

RE: Llano River Bridge Collapse in Texas

Quote (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...
Only sharing because I saw that the remnants of Willa were will likely impact the East Coast as well this weekend (and bring more misery to Texas as well). And you mentioned that you try to pay attention to this stuff.

1994 had three Cat 5 hurricanes in the E. Pacific. Maybe you've missed the last two Cat 5s in 2018 because they've both happened in the last couple of weeks. But we've now tied the 1994 and 2002 record for Cat 5s with three, and surpassed the 2015 Record of seven Cat 4 or greater by three (now at ten on the season). That makes 2018 to be the most intense (Accumulated Cyclone Energy) in nearly 50 years of reliable measurements (since 1971). Just saying...

1994:


2018:

RE: Llano River Bridge Collapse in Texas

interesting tidbit for those who question the “1-percent AEP flood” criteria

Quote (https://pubs.usgs.gov/gip/106/pdf/100-year-flood-h...)

The 1-percent AEP flood has a 1-percent chance of occurring in any given year; however, during the span of a 30-year mortgage, a home in the 1-percent AEP (100-year) floodplain has a 26-percent chance of being flooded at least once during those 30 years! The value of 26 percent is based on probability theory that accounts for each of the 30 years having a 1-percent chance of flooding.

RE: Llano River Bridge Collapse in Texas

Quote (cvg)

interesting tidbit for those who question the “1-percent AEP flood” criteria

The formula is for the % probability of at least 1 occurrence in a particular number of years is: 100(1-(1-1/x)^n)
where x is the annual return period of the event (e.g. "100"-year storm) and n is the number of years for which you are assessing it could occur.

RE: Llano River Bridge Collapse in Texas

cvg - I'm 90% sure that this is just a simple binomial probability.
Success rate = p = 0.01 (forgive the term; success just means that event happens)
n = number of trials = 30 (one per year)
Number of successes = 1 or more
Likelihood = 26% for 1 or more (agrees with USGS, which is nice)
Likelihood = 22% for exactly 1 event
Likelihood = 74% for exactly 0 events

100-year event as a standard isn't so high after all, considering the damage levels.

Statistically, you could have (10) "100-year event" storms in 10 years or zero in 100 years. When many events occur back to back in the same year or consequential years, consider that your physical model might be wrong. Or you're just unlikely, like when New Zealand had a long string of destructive earthquakes 2010 thru 2011. Even if you consider that as a single event, that's extremely rare in the modern era.
Back to the original post.
Extremely rare events sometimes occur. Sometimes multiple extremely rare events occur back to back. If spending 5% extra gets you 30% more robustness to the unknown, I don't need any more math to convince me that's a good bargain. Just need someone to scratch up that extra 5%.
If using the term climate changes gets me that extra 5%, then sign me up.

RE: Llano River Bridge Collapse in Texas

Mongrel - I agree with your point. I HATE that people want to spent trillions of dollars on reducing CO2 levels being emitted and yet it appears there is almost no care care at all about all the other more hazardous pollution we are putting into the environment.

Spartan5 - Your second sentence twisted what I wrote into something different. It's pathetic that you feel the need to repeatedly do that kind of thing to prove you're right. It's a real big surprise that were waiting with crossed fingers that another cat5 hurricane would develop so you could jump all over my post.

RE: Llano River Bridge Collapse in Texas

Speaking of how 'weather events' can impact parts of our planet, it was revealed today that the Hawaiian Archipelago has 'lost' one of its 'islands' as the result of a hurricane earlier this month:

Remote Hawaiian Island Wiped Off The Map

“This event is confronting us with what the future could look like,” one federal scientist said about the loss of East Island, caused by Hurricane Walaka.


https://www.huffingtonpost.com/entry/hawaii-east-i...

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EX-Product 'Evangelist'
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RE: Llano River Bridge Collapse in Texas

I recall reading in years past where they built a dam up there somewhere in central Colorado, with the intent of using the water it for irrigation. So they built the dam, and then never could get the lake to fill with water. It turned out that they had measured the rainfall for 10 years prior to building the dam, only, unbeknownst to them, those were ten of the rainiest years on record, so the lake just didn't happen.

RE: Llano River Bridge Collapse in Texas

That's a pretty big "whoops"

RE: Llano River Bridge Collapse in Texas

JStephen, a similar thing happened during the writing of the water compact for the Colorado River. They used 3 very wet years to divy up the water each state could take take from it and its tributaries. If Wyoming and Colorado ever took their allowed shares, the river would be dry before it reached California. I read that they're working on a new compact now.

RE: Llano River Bridge Collapse in Texas

"Remote Hawaiian Island Wiped Off The Map"

Oooo, scary stuff...until you realize it happens all the time and it has been happening forever. That little "spit of white sand" is no different than the numerous others that have come and gone over the years. You should know better than to take anything the Huffington Post says at face value.

RE: Llano River Bridge Collapse in Texas

Quote (HotRod10)

If Wyoming and Colorado ever took their allowed shares, the river would be dry before it reached California. I read that they're working on a new compact now.
I live in a Great Lakes state. California has had their eye on us for years. I'm sure some year in the not-distant future some politicos here will think it's a great idea and hash out a deal to let them have it. After all, misery loves company.

Brad Waybright

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

RE: Llano River Bridge Collapse in Texas

2
I've worked at 2 nuclear power plants that were designed with extreme flood events (~500 year) in mind. One in Mississippi and one in Nebraska. Both plants experienced flooding well beyond their design basis in the last 10 years. I worked on a design for a nuke in Florida that considered a design flood elevation much greater than the design flood of the plant already existing on that site.

I'm currently working on a design for a large municipal utility facility in coastal Florida, for which an extensive study was performed by one of the largest engineering firms in the world to determine the expected sea level rise by the year 2075. Based on that study (48" expected sea level rise, much greater than the sea level rise that was hypothesized only a few years earlier for that nuclear plant I mentioned, which is located only 20 miles away!), the elevation of the mat foundation will be raised up at a significant cost to taxpayers.

Good thing climate change isn't real, cuz I was starting to really get concerned there for a minute! I'll call up the mayor of Miami and tell him not to worry, we can lower the building back down...

Real science, real phenomena, real engineering.

RE: Llano River Bridge Collapse in Texas

Is that study public by any chance? Or will it be in the future?

RE: Llano River Bridge Collapse in Texas

"...the expected sea level rise by the year 2075."

Did they use term "expected"? I've seen "anticipated" used in those type of studies, which is much different. When designing infrastructure where failure would mean the loss of life may be catastrophic, it's normal to design for a range of possibilities that includes even unlikely scenarios. Just because a nuke plant design is adequate for 4 feet of sea level rise, only means it is a real possibility, not that it is certain, or even likely.

RE: Llano River Bridge Collapse in Texas

I'm not sure if this particular study is public domain or not, but here is a related link that discusses the actions being taken as a result of the study, among others: Link

I think places like Austin and Houston will have to adapt not only to climate change effects, but like stookeyfpe was saying, they will also need to update their flood projections to realistically take into account the effects of urbanization. Hopefully we at least learn from these disasters/failures and don't just rebuild or continue to build the exact same way.

RE: Llano River Bridge Collapse in Texas

2
There's always going to be a cost vs. risk balancing act when it comes to infrastructure improvements. There is only a finite amount of funding to improve the functionality and safety of roadways, bridges, etc., so the chances of a bridge getting washed away in a particular magnitude of flood and what it would cost to make it so that it doesn't, have to be weighed against the improvements that could be made elsewhere. Every dollar that could have been spent on making that bridge able to withstand this flood, is a dollar that was instead spent elsewhere, to upgrade a different bridge, maybe to replace aging or substandard safety railings so that the next SUV to hit the rail doesn't break through and crush the driver when it lands.

I believe making blanket statements about what should have been done in the design of this bridge, without any knowledge of the costs involved, is frankly rather arrogant. The people who have to make these decisions face the impossible task of keeping the system safe and functional without enough money to do either. If they could predict the future as well as all of us can predict the past, perhaps they would have chosen differently. Then again, no lives were lost when this bridge washed away, so even in hindsight perhaps it was better to spend the limited resources on protecting people's lives.

RE: Llano River Bridge Collapse in Texas

Right. Check out the document I linked to and you will see that Miami has undertaken a comprehensive cost-benefit analysis based on the results of climate change/sea level rise studies, and has concluded it makes fiscal sense to make the necessary infrastructure changes now. They are spending millions to harden existing essential services facilities as well as changing the design criteria of new infrastructure, including the facility I am currently designing. It's just good fiscal and civic management based on sound scientific evidence. They are just accepting reality and doing what needs to be done to deal with it.

Of course I'm not criticizing the designers of this bridge in TX for designing it with the best available knowledge at the time. But if the design flood has perhaps changed since then due to the information about climate change that we have now, isn't it just prudent engineering to factor that in to the new design?

I realize this discussion is beyond the scope of the original post, but I do believe it's an important discussion for engineers to be having right now. I just wanted to offer my some of my personal experience and views.

RE: Llano River Bridge Collapse in Texas

Bridge was designed to withstand the 50 year flood and built in 1969. Looks like they nailed it!

RE: Llano River Bridge Collapse in Texas

"It's just good fiscal and civic management based on sound scientific evidence."

Let's be clear, the evidence supports that a significant rise in sea level is possible, and therefore it is prudent to design for that possibility. The fact that the City of Miami is preparing for a particular rise in sea level does not reflect a likelihood of that eventuality.

RE: Llano River Bridge Collapse in Texas

Quote (bones206)

I've worked at 2 nuclear power plants that were designed with extreme flood events (~500 year) in mind. One in Mississippi and one in Nebraska. Both plants experienced flooding well beyond their design basis in the last 10 years.
Witness the Fukushima Daiichi accident. The design basis for protection against tsunami was 3.1 meters height. The actual tsunami was around 13 meters or greater. This does not mean the tsunami threat had increased, but rather the original prediction was wrong.

Brad Waybright

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

RE: Llano River Bridge Collapse in Texas

Fukushima/TEPCO had also been warned that they weren't adequately prepared for a strong tsunami and essentially waved it off. Additionally, putting the backup equipment in the basement just sounds like poor planning.

RE: Llano River Bridge Collapse in Texas

Also, it's commendable that the county is taking a proactive approach and attempting to strengthen their infrastructure while they can. Hopefully it's good foresight.

RE: Llano River Bridge Collapse in Texas

Quote (RVAmeche)

Fukushima/TEPCO had also been warned that they weren't adequately prepared for a strong tsunami and essentially waved it off.
I realize the understanding of the threat increased over the years, but the plant can only be built to the design basis that is understood at the time. My point is that just because a beyond-design-basis event occurred does not mean that the actual threat increased, but rather that the design basis criteria was wrong.

Brad Waybright

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

RE: Llano River Bridge Collapse in Texas

Oh I agree. I was just saying that they had (or should have) become more aware of the threat preceding the event but did not implement changes that may have saved the plant, such as relocating the emergency generator or backup batteries.

RE: Llano River Bridge Collapse in Texas

In the case of Fukushima, the critical generators could have been moved to a higher location without a major redesign of the plant.

At the core of most of these disasters is the cost element that was traded against what level of risk could be reasonably defended in the case of an actual disaster. This is why industries are often not allowed to regulate themselves; their financial incentives are invariably overly skewed in the opposite direction of safety and conservatism.

TTFN (ta ta for now)
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RE: Llano River Bridge Collapse in Texas

bones206,

Maybe a small point as regards to the flooding of the Missouri river, but maybe the Army Corp should have looked a little farther ahead as to what happens to the nuclear station downstream if the reservoirs are too full and need to dump water like crazy to avoid overtopping.

RE: Llano River Bridge Collapse in Texas

Point taken, but usually upstream dam scenarios are taken into account when determining the design basis flood elevation of the plant.

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