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Thalweg vs. Thread

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(@horseshoes-handgrenades)
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What do you consider the definition of thalweg and thread to be??ÿ My coworker is sitting for a state exam on Monday and brought this to my attention.?ÿ I always thought that Brown's definition to be correct, not the 2009 BLM Manual and that the thalweg was the deepest part of the channel.?ÿ I don't have a personal copy of Black's so I can't see if it has definition.?ÿ?ÿ

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Posted : 25/02/2023 2:54 pm
not-my-real-name
(@not-my-real-name)
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They always ask that question. Thalweg is the deepest part of the channel. Thread is the center of the stream. Your state laws may differ.

 

 
Posted : 25/02/2023 2:57 pm
(@holy-cow)
Posts: 25292
 

To most people. they would seem to be identical.  Anything that requires 200 words to explain is BS.

Neither exists in nature.  They are concepts.

 
Posted : 25/02/2023 3:14 pm
not-my-real-name
(@not-my-real-name)
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@holy-cow 

I agree. What is the point in learning these archaic words in order to become a land surveyor? Thalweg is not even an English word.

It is just brabble that some cockalorum thought up to fuzzle the uninitiated future Land Surveyors.

 
Posted : 25/02/2023 3:23 pm
(@jitterboogie)
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@not-my-real-name 

welcome to the chicanery that is the FS and PS today....

 
Posted : 25/02/2023 3:35 pm
(@bill93)
Posts: 9834
 

Those two sources give three definitions, and the names for the deepest part are contradictory.

-Deepest part

-Line of navigation

-center of stream

There is also midway between the banks.

The very name translated from German thalweg to "valley way" says the Manual has it backward. Black's, Brown, Mirriam-Webster, and Wikipedia agree thalweg is deepest line.

 
Posted : 25/02/2023 4:49 pm
(@bill93)
Posts: 9834
 

There was a relevant forum thread a few years ago with some case history.

https://rpls.com/community/surveying-geomatics/thread-of-river/

 
Posted : 25/02/2023 4:50 pm
(@nate-the-surveyor)
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I think y'all is all wet. Or the stream is dry.

N

 
Posted : 25/02/2023 6:25 pm
(@duane-frymire)
Posts: 1924
 

Thalweg comes from navigation law.  Thread comes from boundary law.  And then they mixed them. Political v. private boundaries, equitable considerations considered by the courts, etc..  My best advice is to answer according to the manual if question is on FS or PS.  Answer the other way if question is on State exam.  Especially on the water law questions, and especially in a colonial State, you need to answer differently depending on which exam.

 
Posted : 26/02/2023 4:34 am
(@holy-cow)
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That is what makes this a terrible question to be put on any exam.

Test questions for professional practice licensure should be focused on actual practice concerns, not text book definitions.

 
Posted : 26/02/2023 9:55 am
(@thebionicman)
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@duane-frymire Your post explains itself. Having the line which controls commerce as a political boundary is perfect. Is places States on equal footing..

 
Posted : 26/02/2023 10:28 am
(@john-putnam)
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@duane-frymire Your post explains itself. Having the line which controls commerce as a political boundary is perfect. Is places States on equal footing..

Agreed.  It seems to me that unless you are talking about political divisions then the manual's definition of thalweg is mute.  If a waterway is navigable then the channel is owned by the state and if it is not navigable then the geomorphologic definition of thalweg, which is basically the same as the manual's definition of thread, controls.   Generally speaking, the deepest part of a waterway is not the center of the channel.

Wow, my degree in geomorphology finally paid off.

 

 
Posted : 26/02/2023 1:10 pm
(@holy-cow)
Posts: 25292
 

Many of our river bottoms/creek bottoms are weathered/eroded limestone.  All sorts of minor pooling opportunities.  There isn't a single little trickle of water that would continuously be found so as to define a thread/thalweg.  The actual bank lines are far from being smooth continuous lines.  Attempting to define a pair of lines for which a midpoint between them could be calculated would require something like scanning as opposed to common field measurements.  That would be an expense that would be far too great to justify its use simply to be MORE precise.

 
Posted : 26/02/2023 1:44 pm
(@jitterboogie)
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@holy-cow 

it depends....

 
Posted : 26/02/2023 9:33 pm
(@duane-frymire)
Posts: 1924
 

@john-putnam And unlike in PLSS, some colonial States Nav in fact does not equal Nav in law, can be Nav in fact and still private bed.

 
Posted : 27/02/2023 4:29 am
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