vallée en toit

English translation: perched river

09:59 Dec 17, 2020

French to English translations [PRO]
Science - Environment & Ecology / flooding and levee spillways

French term or phrase: vallée en toit

This term is from a French book on river levee spillways. The best I could find is “perched” (more often "perched riverbed" "perched channel", but I’m not so sure and neither is the author.
Here is a sentence from the book:
“L’attention des gestionnaires de digues devra donc se porter sur ces conditions, notamment si la topographie de la zone protégée est en pente vers le coteau (cas classique d’une **vallée en toit**).”

And from other sources in French:
“Les écoulements éventuels par-dessus les digues se fassent en condition dénoyée, c'est-à-dire que la charge hydraulique à l’aval de la digue n’influence pas la charge à l’amont (dans le lit
mineur). Cette condition est vérifiée dans le cas présent, car le lit mineur du Rhône est à une
altitude plus élevée que les plaines constituant le lit majeur (**vallée en toit**).”

“Plus en aval encore, dans les zones de plaine, de plus en plus sinueux, le cours d’eau adopte un tracé à lit unique et à méandres. Il est nettement calibré. Dans les méandres de piedmont, le transport solide est mixte (suspension et charriage), alors qu'en plaine il a lieu quasi-exclusivement par suspension. Il est composé de sables fins et de limons. Les rivières de plaine déposent sur leurs rives des sédiments fins transportés en suspension lors des
crues. Il se forme ainsi des bourrelets de berge et le point bas de la vallée se trouve en position intermédiaire entre la berge et le coteau. On parle de vallée en toit”
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&c...

Diagram in http://pp.ige-grenoble.fr/pageperso/belleudp/encrequicoulede...

Any other ideas, or confirmation of "perched" would be great!

Diana Huet de Guerville KudoZ activity Questions: 92 (7 open) (3 without valid answers) (10 closed without grading) Answers: 12 France
Local time: 05:31

English translation:perched river

Explanation:
I can find plenty of references for 'perched river' e.g.

https://www.stblaisenp.co.uk/starr
https://slideplayer.com/slide/13169759/ (slide 18 of 29)
https://docplayer.fr/44563655-Cartographie-des-zones-inondab... (slide 28 of 43)

Also, in the book "River Mechanics"
https://books.google.co.uk/books?id=uOrdh7pOZ9wC&pg=PA289&lp... (page289)

These all say that the river flow has brought sediment down during times of flood. The successive sediment deposits have built up at the banks to form levees. The water can overflow these in times of flooding and (as mentioned in your source text) can flood the surrounding floodplain areas.

'Perched channel' seems to be used mainly for lava flows rather than water.
'Perched river bed' seems to be used rarely and many references are from the same original source
'Perched river valley' - I can only find one reference to at https://www.leg.mn.gov/docs/pre2003/other/800875.pdf .

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Note added at 2 hrs (2020-12-17 12:32:45 GMT)
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Please ignore the reference at https://slideplayer.com/slide/13169759/ It is more related to the position of the water table than the crossectional topography of the section of the river in this case.

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Note added at 1 day 12 hrs (2020-12-18 22:23:33 GMT)
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The reason for the term 'perched river' is that the build up of sediment has created levees at the banks and caused the riverbed to rise. This results in the level of the river baseflow being higher (sometimes significantly higher) than the surrounding floodplain. As a result, when the river overflows or breaks the levees, there is rapid flooding of the rest of the valley and often dangerous, high velocity floodplain flows. For more reference and images, see the following -

https://books.google.co.uk/books?id=c-h4AgAAQBAJ&pg=PA288&lp...
https://www.rms.nsw.gov.au/projects/01documents/blackadder-s...
https://www.gov.mb.ca/mit/wms/floodcontrol/arbasin/assiniboi... (with pictures)
https://cawaterlibrary.net/wp-content/uploads/2019/07/Append...

Selected response from:

Althea Draper
United Kingdom

Grading comment

Selected automatically based on peer agreement.
4 KudoZ points were awarded for this answer

Summary of answers provided

raised riverbed

Ben Gaia

2 +2

perched river

Althea Draper

roof-shaped valley profile / cross-section

Thomas Miles

3 -1

the top of a valley

Lisa Rosengard

Discussion entries: 1

Answers

7 hrs confidence:

raised riverbed

Explanation:
This is the correct geographical term for a river whose bed has been raised by many floods and/or the building of levees.

Example sentence(s):

The rivers are braided, a typical feature here and on the Canterbury Plains, where there is a high loading of eroded gravels and a raised riverbed. Braided rivers are highly valued by the region’s farmers and orchardists for irrigation.

https://www.worldwildlife.org/ecoregions/aa0408

Ben Gaia
New Zealand
Local time: 15:31
Specializes in field
Native speaker of:

English
PRO pts in category: 4

8 hrs confidence:

roof-shaped valley profile / cross-section

Explanation:
Just seen the diagram. We are essentially talking about the shape of its cross-section. Feel free to explore other options with geometric terminology.

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Note added at 8 hrs (2020-12-17 18:36:46 GMT)
--------------------------------------------------

You could of course try naming the features that give it this 'roof shape'. If they are levees, you could try 'river valley with pronounced levees'.

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Note added at 1 day 9 hrs (2020-12-18 19:25:07 GMT)
--------------------------------------------------

The learned equivalent of 'roof-shaped' is 'tectiform'.

Thomas Miles
France
Local time: 05:31
Specializes in field
Native speaker of:

English

2 hrs confidence:

peer agreement (net): +2

perched river

Althea Draper
United Kingdom
Specializes in field
Native speaker of:

English
PRO pts in category: 12

Grading comment

Selected automatically based on peer agreement.

Peer comments on this answer (and responses from the answerer)

disagree

Ben Gaia: not a common usage

5 hrs

-> It is common usage and there are plenty of references in books and academic works. https://www.google.com/search?q="perched river"&ei=7q_bX9y6C...

agree

Rachel Fell: https://eprints.soton.ac.uk/415085/1/Zhang_et_al_2017_Hydrol...

10 hrs

-> Thanks Rachel

agree

writeaway

12 hrs

-> Thanks writeaway

disagree

Thomas Miles: I dislike the use of the adjective 'perched' (which suggests up high like a hanging valley, rather than slightly elevated). And no, as translators we are 'stakeholders' in terminology and have a right to reject terms at odds with the underlying concepts

1 day 6 hrs

-> So you think that translators should be telling geologists, engineers and geographers that they should change their terminology because we don't like it?!?! Get real.

agree

Yvonne Gallagher: Well-researched and referenced

10 days

-> Thanks Yvonne

agree

Carol Gullidge: I think you're on to something, although the term is "vallée" and not "rivière" or "cours d'eau", etc

12 days

12 hrs confidence:

peer agreement (net): -1

the top of a valley

Explanation:
The condition is checked presently as the smaller riverbed of Rhône is at a higher altitude than the plains which form the larger riverbank.

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Note added at 9 days (2020-12-26 12:23:43 GMT)
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Selon le diagramme, le petit lit de la fleuve est au-dessus des deux lits majeurs de la même fleuve.

(According to the diagramme, the minor riverbed is above both the major riverbeds of the same river.)

Example sentence(s):

"Cette condition est vérifiée dans le cas présent, car le lit mineur du Rhône est à une altitude plus élévée que les plaines, constituant le lit majeur."

Lisa Rosengard
United Kingdom
Local time: 04:31
Native speaker of: English
PRO pts in category: 4

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English translation: perched river

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