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:

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[LionelHutz]

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.

 

[JohnRBaker]

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/entr...ls-climate-change_us_5bcf2a8ee4b055bc9484e803

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

 

[JStephen]

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.

 

[RVAmeche]

That's a pretty big "whoops"

 

[BridgeSmith]

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.

 

[BridgeSmith]

"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.

 

[thebard3]

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.

 

[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. 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.

 

[RVAmeche]

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

 

[BridgeSmith]

"...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.

 

[bones206]

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.

 

[BridgeSmith]

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.

 

[bones206]

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.

 

[Spartan5]

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

 

[BridgeSmith]

"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.

 

[thebard3]

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.

 

[RVAmeche]

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.

 

[RVAmeche]

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.

 

[thebard3]

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.

 

[RVAmeche]

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.