What is going on at Mansfield dam?

[Pato del Muerto 52,489]

Just now, Mr. Blutarsky said:

Initial report was of unauthorized personnel in the tunnels, but LCRA just released an update stating that no one was found. 

 

https://www.kxan.com/news/local/travis-county/large-law-enforcement-presence-responding-to-situation-near-mansfield-dam/

He slipped and fell into the wet concrete below. 
buried in that gray tomb that knows no sound, but he is still around. 

[Mr. Blutarsky 133]

1 minute ago, Pato del Muerto said:

He slipped and fell into the wet concrete below. 
buried in that gray tomb that knows no sound, but he is still around. 

and around and around and around and around and around. 

[Anastasis 23,469]

Seems to me that these dams are really soft targets, with potential for catastrophic results.  

[Cajun 11,705]

47 minutes ago, MissingInAction said:

If this loon has any idea what he is doing there is no way they are rooting him out of that. Let's just hope he isn't about to blow the whole dam thing. 

I've heard reports that he had the Chingadero Enchilada plate at Dart Bowl earlier today so it appears that is precisely his intention.

[Pato del Muerto 52,489]

8 minutes ago, Cajun said:

I've heard reports that he had the Chingadero Enchilada plate at Dart Bowl earlier today so it appears that is precisely his intention.

Biological warfare. And chemical. Can’t rule out nucular either. 

[clapclapclap 9,000]

23 minutes ago, Mr. Blutarsky said:

Initial report was of unauthorized personnel in the tunnels, but LCRA just released an update stating that no one was found. 

The real BigFan is still on the loose?

[Cajun 11,705]

Quote

Biological warfare. And chemical. Can’t rule out nucular either. 

 

There is no defense brother, trust me.

After discovering that meal I haven't had to hire a pest exterminator since.

Edited January 14, 2020 by Cajun

[Bevo 13,576]

Interestingly, the company that built the dam was sourced by Korn Ferry.

[Biff Tannen 45,673]

Quote

LCRA says it promptly called law enforcement and a widespread search of the dam began to find the “gentleman” who the employee said “ran by him.”

But no one was found in the top-to-bottom search of the facility, LCRA says.

[atomheartbevo 89,648]

Press statement/conference segment

[atomheartbevo 89,648]

43 minutes ago, Somnio said:

Good God, that is a scary thought.

Depends on where you live.

 

[Bevo 13,576]

2 minutes ago, atomheartbevo said:

Depends on where you live.

 

I'm good.

[immortal13 4,059]

4 minutes ago, atomheartbevo said:

Press statement/conference segment

Well I feel safer now

[Cajun 11,705]

What we have here is a non-terminal repeating phantasm, or a class 5 full roaming vapor...

[Jiggy-Z 3,432]

Is this what they mean when they say its infrastructure week?

[Biff Tannen 45,673]

30 minutes ago, atomheartbevo said:

Depends on where you live.

 

That starts at Tom Miller dam.

[Mrs Whiggins 13,050]

He was probably just not a very good spy is all and ran away when he discovered that if you're going to go phishing or plant a logic bomb, a dam is not the best place to do it. It's hard to get good help these days.

[Mr. Blutarsky 133]

39 minutes ago, atomheartbevo said:

Depends on where you live.

 

Not to burst the bubble, but that cut off is Tom Miller Dam. That is flood projections for is Lake Austin came to town, not Travis. If Mansfield ever goes, Austin is no more. 

 

[atomheartbevo 89,648]

It honestly wouldn't surprise me if this was some "urban explorer" type looking to get some footage for their YouTube channel - got to be in the top 5 of homegrown content, behind unboxing videos, video game streaming, reaction videos, prank videos.

Or Lou was drinking again.

[Pato del Muerto 52,489]

Is Mansfield the start or end of town lake?  

[hayden_horn 11,362]

5 minutes ago, Pato del Muerto said:

Is Mansfield the start or end of town lake?  

Neither. It is the end of travis and the beginning of austin. Tom miller is the start of town lake. 

Edited January 14, 2020 by hayden_horn

[Pato del Muerto 52,489]

Gotcha. So a lot of water behind it...usually. 

[atomheartbevo 89,648]

12 minutes ago, Mr. Blutarsky said:

Not to burst the bubble, but that cut off is Tom Miller Dam. That is flood projections for is Lake Austin came to town, not Travis. If Mansfield ever goes, Austin is no more. 

Closest I could find.  A lot of that would still flow south.

[Ghost of LL 15,531]

29 minutes ago, Mr. Blutarsky said:

Not to burst the bubble, but that cut off is Tom Miller Dam. That is flood projections for is Lake Austin came to town, not Travis. If Mansfield ever goes, Austin is no more. 

 

I would suspect that the inundation maps are pretty similar.

Downstream from Mansfield, the Colorado flows through a pretty significant gorge all the way to Tom Miller.  If Mansfield were to fail, that water would flow at high speed through that gorge until it hit Tom Miller.  

At that point, the flood would overtop Tom Miller as soon as it got above 519 feet msl (i.e., the elevation of the top of the dam).  Overtopping Tom Miller Dam would cause it to fail within a short amount of time.  Tom MIller's failure would quickly lower the level of the flooding of Lake Austin.

So basically, anything upstream of Tom Miller Dam that is below about 530 feet msl would probably be inundated in that type of scenario.  But looking at a topographical map upstream shows that there's not just a whole lot below that elevation.

But hey--don't trust me.  I'm not an engineer and I haven't done the H&H modeling.

 

[HiggyBaby 2,529]

1 hour ago, atomheartbevo said:

Press statement/conference segment

[Born to Run 6,569]

Depends on where you live.
 

That's applicable for Tom Miller not Mansfield. The latter would send a massive wall of water downstream wiping out a big chunk of Steiner instantly just as an example.

I'm 30' above the top of Mansfield with a nifty view of it from my living room. I'll rotate my phone to landscape if shit ever goes down.

Lcra will probably just close Jessica Hollis permanently now under the guise of security need. They already moved the security buoys further down last year and cockblocked my little fishing spot.

[Mighty fine 169]

I would suspect that the inundation maps are pretty similar.
Downstream from Mansfield, the Colorado flows through a pretty significant gorge all the way to Tom Miller.  If Mansfield were to fail, that water would flow at high speed through that gorge until it hit Tom Miller.  
At that point, the flood would overtop Tom Miller as soon as it got above 519 feet msl (i.e., the elevation of the top of the dam).  Overtopping Tom Miller Dam would cause it to fail within a short amount of time.  Tom MIller's failure would quickly lower the level of the flooding of Lake Austin.
So basically, anything upstream of Tom Miller Dam that is below about 530 feet msl would probably be inundated in that type of scenario.  But looking at a topographical map upstream shows that there's not just a whole lot below that elevation.
But hey--don't trust me.  I'm not an engineer and I haven't done the H&H modeling.
 

In general terms, assuming level pool routing, you aren't far off. However in this case, you need to look at a more energy dynamic model since the reach distance between Mansfield and Tom Miller is not great enough to attenuate the flood wave before hitting Tom Miller. The ensuing flood wave would likely be significantly higher than the top of the dam.... pretty much just cover it up and sweep it away. It's that extreme wave height that'll flood a much greater area.

[ClubWhatever 12,128]

It was a dam broaching mistake

[Ghost of LL 15,531]

16 minutes ago, Mighty fine said:

26 minutes ago, Ghost of LL said:

I would suspect that the inundation maps are pretty similar.
Downstream from Mansfield, the Colorado flows through a pretty significant gorge all the way to Tom Miller.  If Mansfield were to fail, that water would flow at high speed through that gorge until it hit Tom Miller.  
At that point, the flood would overtop Tom Miller as soon as it got above 519 feet msl (i.e., the elevation of the top of the dam).  Overtopping Tom Miller Dam would cause it to fail within a short amount of time.  Tom MIller's failure would quickly lower the level of the flooding of Lake Austin.
So basically, anything upstream of Tom Miller Dam that is below about 530 feet msl would probably be inundated in that type of scenario.  But looking at a topographical map upstream shows that there's not just a whole lot below that elevation.
But hey--don't trust me.  I'm not an engineer and I haven't done the H&H modeling.
 

Read more  

In general terms, assuming level pool routing, you aren't far off. However in this case, you need to look at a more energy dynamic model since the reach distance between Mansfield and Tom Miller is not great enough to attenuate the flood wave before hitting Tom Miller. The ensuing flood wave would likely be significantly higher than the top of the dam.... pretty much just cover it up and sweep it away. It's that extreme wave height that'll flood a much greater area.

So what do you reckon?  Because looking at the topo map, it doesn't look like there's just a whole lot of acreage downstream from Mansfield that is below 600.*  I mean, there's no way that flood wave would go above 600, would it?

 

 

* To be clear, there are a fair number of homes.  There would be property destruction and loss of life.  But speaking solely from the standpoint of depicting an inundation map, it's not going to look very significant in terms of acreage because of the narrowness of the gorge and the steepness of the escarpment.

[Mighty fine 169]

LLs post got me to thinking about what may happen if Mansfield did go. I imagine the flow regime goes subcritical to super critical through the busted dam, then a hydraulic jump downstream before the foodways narrows at the cliffs and then subcritical until about mopac, then supercritical again where the foodways spreads out. The subcritical portions will be flowing higher and slower (relatively) compared to the shallower and faster super critical sections. That said, probably isn't worth differentiating the flow profiles as either would be catastrophic

[Ghost of LL 15,531]

1 minute ago, Mighty fine said:

LLs post got me to thinking about what may happen if Mansfield did go. I imagine the flow regime goes subcritical to super critical through the busted dam, then a hydraulic jump downstream before the foodways narrows at the cliffs and then subcritical until about mopac, then supercritical again where the foodways spreads out. The subcritical portions will be flowing higher and slower (relatively) compared to the shallower and faster super critical sections. That said, probably isn't worth differentiating the flow profiles as either would be catastrophic

And it presumably differs depending on whether we're talking about the probable maximum flood or the sunny-day scenario.  But since we're talking about a terrorist attack or something of that nature, we should probably stick with the sunny-day scenario.

[Mighty fine 169]

Man, I posted my last response before reading your follow up.

Note, I have not studied this in great detail, so a lot of what I'm saying is based on my judgment and general knowledge of the topography.

Depending on how fast lake travis drops after Mansfield fails, yes, it could conceivably reach that high.

[Mighty fine 169]

And it presumably differs depending on whether we're talking about the probable maximum flood or the sunny-day scenario.  But since we're talking about a terrorist attack or something of that nature, we should probably stick with the sunny-day scenario.

 

Well had to rethink what I wrote here. I agree with this in the sense that the mode of failure would dictate severity of the event. However, I think the discharge due to complete dam failure would be an order of magnitude more than the upstream inflow.... but I may be way off on this

 

[Ghost of LL 15,531]

2 minutes ago, Mighty fine said:

5 minutes ago, Ghost of LL said:

And it presumably differs depending on whether we're talking about the probable maximum flood or the sunny-day scenario.  But since we're talking about a terrorist attack or something of that nature, we should probably stick with the sunny-day scenario.

Exactly, that dovetails in to my what I was getting to regarding rate of water level drop in travis

. . . and I presume that in the sunny-day scenario, the water level probably wouldn't go above 600'.  Which means that the inundation map upstream from Tom Miller Dam wouldn't look like a lot.

So--to wrap up this nerd talk, the inundation map for Mansfield Dam probably only needs to really show inundation downstream from Tom Miller Dam.

[Parliament 14,255]

2020 Surly Hydrology talk not going away.

[RPM 26,318]

So was this whole thing some kind of dam hoax?

[Mighty fine 169]

I had to correct my quoted post. Depending on the downstream foodways it could conceivably rise that high under a sunny day scenario. The only difference sunny vs pmp make in this case is how long the rate of water level drop.

You could argue that pmp would be more likely to lead to total dam failure compared to terrorist activity (ie, no dam vs a whole in the spillway), and that's a valid challenge (and thinking about it more, probably more correct). I'm assuming a complete uncontrolled release in my 'analysis' which is picking a little from pile a and a little from pile b; mix em together and its worth about a pile of shit.

[atomheartbevo 89,648]

19 minutes ago, Parliament said:

2020 Surly Hydrology talk not going away.

It is Tuesday.  

[Steamboat1874 4,056]

Do you realize how much explosive power it would take to even make a dent in that dam.?

It would take way more than one man could carry unless it was a nuke.

[atomheartbevo 89,648]

12 minutes ago, Steamboat1874 said:

Do you realize how much explosive power it would take to even make a dent in that dam.?

It would take way more than one man could carry unless it was a nuke.

What about an entire high school football team that spent the evening at a Taco Bell?

[jettrink 40]

Just found out my son(leo) was the first one into dam.  He said it is an amazing structure with pipes and shit going every direction.  He said they cleared it, but I said there must be a million places to hide in there.  He disagreed of course, as he always has.

[Mighty fine 169]

What about an entire high school football team that spent the evening at a Taco Bell?

The erosive velocity of the septic river emanating from within the tunnels would likely do it

[Junior Miller 1,502]

Well that's a dam shame

[tx 3 putt 76,905]

Release it, the bays need a good flushing 

[Anastasis 23,469]

1 hour ago, Steamboat1874 said:

Do you realize how much explosive power it would take to even make a dent in that dam.?

It would take way more than one man could carry unless it was a nuke.

How about a flotilla of pontoon boats rigged up like OKC with fertilizer bombs?

[KaiserSoze 998]

It is Tuesday.  

Tuesday is when we eat the birds.

[futureman 22,453]

 

1 hour ago, jettrink said:

Just found out my son(leo) was the first one into dam.  He said it is an amazing structure with pipes and shit going every direction.  He said they cleared it, but I said there must be a million places to hide in there.  He disagreed of course, as he always has.

so they haven’t found him?  was he texting from inside the dam or did he escape unseen?

[SurlyBDR 22,773]

CCTV footage from this morning, before the LCRA employees arrived 

[Steel Shank 9,422]

I know some guys that were catching crawdads below the damn back in the late 80s and went up into the tunnels. You could slide down/out of them into the lake due to the slick mossy stuff from a constantly slow trickle of water. Some guys I know.

I think we should bring in Plonsky to help figure this mess out.


Sent from my iPhone using Tapatalk

[Little Steven 57]

4 hours ago, Ghost of LL said:

. . . and I presume that in the sunny-day scenario, the water level probably wouldn't go above 600'.  Which means that the inundation map upstream from Tom Miller Dam wouldn't look like a lot.

So--to wrap up this nerd talk, the inundation map for Mansfield Dam probably only needs to really show inundation downstream from Tom Miller Dam.