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Why do I think there's more news coming up??
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JohnRBaker
Mechanical
And you reckon that this is somehow an 'Engineering Failure' or something, eh?
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
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
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- #3
I find this interesting since our West Coast weather has made a dramatic change over the last ten years or so. The weather is compellingly different. I wonder if all this isn't somehow related to the sudden suspension of airline flights? The uniform dispersion of exhaust from 315,000,000 gallons of fuel that was burned daily.
Keith Cress
kcress -
Keith Cress
kcress -
The suspension of flights over the US for several days after 9/11 caused a greater difference in daytime/nighttime temperatures due to fewer high-altitude contrails. NOVA had a program on that.
For China right now the big issue is the Three Gorges Dam. Even during the years of construction there was a great deal of issues surrounding corruption and workmanship. Chinese officials, to reassure everyone, boasted that it was built for a 10,000 year flood. In the time since then they state a 100 year flood. Now they have a 100 year flood in progress. This boast came from government officials so it is more of a political statement than an engineering assessment.
For China right now the big issue is the Three Gorges Dam. Even during the years of construction there was a great deal of issues surrounding corruption and workmanship. Chinese officials, to reassure everyone, boasted that it was built for a 10,000 year flood. In the time since then they state a 100 year flood. Now they have a 100 year flood in progress. This boast came from government officials so it is more of a political statement than an engineering assessment.
The statement "water level behind the massive structure rose more than 15m above flood level" indicates the pond is 15m above flood level. Nothing is said about water levels downstream in article posted by OP, but the wide open floodgates with a +15m pond would unleash a torrent, and is reported elsewhere,
Fox reports that this is "The second highest rainfall in more than a half-century".
I could see a discussion about fit to task in the the context of flood control, which is both an engineering and a political question.
Fox reports that this is "The second highest rainfall in more than a half-century".
I could see a discussion about fit to task in the the context of flood control, which is both an engineering and a political question.
Once dammed and the water regulated by the dam, development along the banks continues - eliminating natural flooding areas that previously protected downstream areas from floods and exposing more people to the risk. Wall breaches are more abrupt than overland flooding, hence less warning.
This happens EVERYWHERE.
The simple act of damming and developing reduces the timeframe of "100 year flood" by a major factor. In the case of the Yangtze, there have been floods with fatalities and destruction >bn$ in 1998, 2010 and 2016, too.
This happens EVERYWHERE.
The simple act of damming and developing reduces the timeframe of "100 year flood" by a major factor. In the case of the Yangtze, there have been floods with fatalities and destruction >bn$ in 1998, 2010 and 2016, too.
JayMaechtlen
Industrial
"reduces the timeframe of "100 year flood""
Sorry, I don't get it.
Does the presence of dams actually increase the likelihood of flooding when infrequently heavy rainfall occurs?
Jay Maechtlen
Sorry, I don't get it.
Does the presence of dams actually increase the likelihood of flooding when infrequently heavy rainfall occurs?
Jay Maechtlen
I should let SparWeb speak for himself, but I think he is referring to the inevitable land use changes associated with dam building.[ ] Increased stram flow rates, shorter times of concentration, simply covering a large amount of land with permanent water, etc.
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- #13
Well it looks like some pretty wet weather is on the horizon
Jay, and Denial,
Yes that is roughly what I was asserting. When I say "everywhere" I mean it can happen anywhere that a watercourse is given some control by a major project such as damming. Then, land along the banks becomes more desirable for development (housing, industrial, commercial, whatever). That development inevitably changes shore slopes, runoff flows, and on the non-engineering side, the land value which influences political decisions.
Important to note that examples can be cited from any country you choose, and my country, Canada, is no exception. There's no desire to pick on China in what I say. It also happens in Brazil, USA, Germany, and so on. In 2013, much of the Highwood River flooding that ruined parts of the town of High-River Alberta (close to me) have been blamed on over-development of the flood plain and changes to the upstream slopes, which just channeled the slug of water toward the town faster and higher than it would have been with exactly the same amount of rain and runoff, if development wasn't there.
I'm not an environmental engineer so my understanding of the subject is weak. I just go by basic fluid dynamics and volume available to the river, which is what makes sense to me. A watershed with a slope of 100:1 being replaced by a 5 meter rockwall to carry a road will remove some cubic kilometers of volume that a flood could occupy. In my jurisdiction, all of this is hotly contested still, so the parts of the debate that pop up in mass media aren't always the most factual ones. It almost resembles the global-warming argument, as in "how could humans possibly cause an act of god such as a flood" while others have plenty of satellite and terrain maps showing exactly how, if only town officials would listen.
Yes that is roughly what I was asserting. When I say "everywhere" I mean it can happen anywhere that a watercourse is given some control by a major project such as damming. Then, land along the banks becomes more desirable for development (housing, industrial, commercial, whatever). That development inevitably changes shore slopes, runoff flows, and on the non-engineering side, the land value which influences political decisions.
Important to note that examples can be cited from any country you choose, and my country, Canada, is no exception. There's no desire to pick on China in what I say. It also happens in Brazil, USA, Germany, and so on. In 2013, much of the Highwood River flooding that ruined parts of the town of High-River Alberta (close to me) have been blamed on over-development of the flood plain and changes to the upstream slopes, which just channeled the slug of water toward the town faster and higher than it would have been with exactly the same amount of rain and runoff, if development wasn't there.
I'm not an environmental engineer so my understanding of the subject is weak. I just go by basic fluid dynamics and volume available to the river, which is what makes sense to me. A watershed with a slope of 100:1 being replaced by a 5 meter rockwall to carry a road will remove some cubic kilometers of volume that a flood could occupy. In my jurisdiction, all of this is hotly contested still, so the parts of the debate that pop up in mass media aren't always the most factual ones. It almost resembles the global-warming argument, as in "how could humans possibly cause an act of god such as a flood" while others have plenty of satellite and terrain maps showing exactly how, if only town officials would listen.
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- #15
Seems a bit melodramaic, and if this is only going to drop the water level in one small area by 70 cm also seems a lot of hope and not much engineering went into the decision making process
Dropping 70cm on a flood plain doesn't sound like much, but can be very significant, when considering the length of the shoreline. If that happens on the length of a long river, aits many times the volume of the river itself.
Satelite maps? Problem is that everyone has an opinion, few of which are based on fact and, if it's based on facts, it's more likely to be facebook facts, or some other equally dubious source, and nobody wants to see any expert derived facts, because that might change their opinion, or actually prove them wrong. I wish every non-expert would take their opinions, write them down and put them where the sun don't shine. A perfect suppository for opinions.
“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"
Satelite maps? Problem is that everyone has an opinion, few of which are based on fact and, if it's based on facts, it's more likely to be facebook facts, or some other equally dubious source, and nobody wants to see any expert derived facts, because that might change their opinion, or actually prove them wrong. I wish every non-expert would take their opinions, write them down and put them where the sun don't shine. A perfect suppository for opinions.
“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"
There are no risk-free options; we always deal with tradeoffs. These are not moral decisions. All engineered systems can have adverse effects. And it is difficult to engineer around systemic gov't corruption.
In the US, dams have been substantially positive. In the Western US, without dams, it would be impossible to reliably provide drinking water to the urban areas, or irrigation to rural areas.
And if climate change is half as real as has been threatened - we need more reservoirs, not less. Like nuclear, more smaller systems would provide redundancy and reduce major failures. That is, when a failure does occur (inevitable), the impact is small. Say, compared to Oroville failing - in California, where new reservoirs are just about impossible to build, so we just make the big reservoirs bigger.
Yes, dams also come with negative consequences, and yes, with failures. As happens with electric cars and airplanes and windmills and wastewater plants.
And if you buy a house downstream of a dam, you shouldn't be contributing to this discussion.
In the US, dams have been substantially positive. In the Western US, without dams, it would be impossible to reliably provide drinking water to the urban areas, or irrigation to rural areas.
And if climate change is half as real as has been threatened - we need more reservoirs, not less. Like nuclear, more smaller systems would provide redundancy and reduce major failures. That is, when a failure does occur (inevitable), the impact is small. Say, compared to Oroville failing - in California, where new reservoirs are just about impossible to build, so we just make the big reservoirs bigger.
Yes, dams also come with negative consequences, and yes, with failures. As happens with electric cars and airplanes and windmills and wastewater plants.
And if you buy a house downstream of a dam, you shouldn't be contributing to this discussion.
The discussion above focused on the flooding downstream of the dam providing flood control.
Here we also see flooding upstream. Any impediment land use plan needs to consider the land that could be flooded during wet weather flood control. Here the pond has risen to +15m (about 50 ft) given any reasonable shore slope that is an enormous land area.
Just a guess - this flood control storage area was not cleared of farms and towns due to the high population density and the demand for land.
This happened in Houston after Harvey, where land use plans did not require flood tolerant construction in the storage area of the Addicks and Barker reservoirs.
Here we also see flooding upstream. Any impediment land use plan needs to consider the land that could be flooded during wet weather flood control. Here the pond has risen to +15m (about 50 ft) given any reasonable shore slope that is an enormous land area.
Just a guess - this flood control storage area was not cleared of farms and towns due to the high population density and the demand for land.
This happened in Houston after Harvey, where land use plans did not require flood tolerant construction in the storage area of the Addicks and Barker reservoirs.
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- #19
This still has the potential of a disaster in the making. ANd remember the Chinese are not famous for being fortrite with impending disasters.
Here's a live-feed of the Three Gorges Dam. For scale - there is a crane just above the letter "R" in the word "WATER" in the title on the feed. Not sure how long it will be up.
There is a report that a large chunk broke off in the last day or so, but it does not seem to have caused any further harm.
While dire predictions have been made in the past that were obviously wrong, failure of this dam would be the most 2020 thing so far.
edit - adding the link seemed appropriate.
There is a report that a large chunk broke off in the last day or so, but it does not seem to have caused any further harm.
While dire predictions have been made in the past that were obviously wrong, failure of this dam would be the most 2020 thing so far.
edit - adding the link seemed appropriate.
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