The options given by the text are: Korodur (a trade mark) or concrete that has been straightened. Some examples:

MSN Encarta - Print Preview - Everglades
... help by converting the Kissimmee River, the source of Lake Okeechobee’s water, from a meandering subtropical stream into a straightened concrete-lined channel ...
encarta.msn.com/text_761574006___4/Everglades.html

reports
... Rivers cannot be put in a straightened concrete river bed, especially with large quantities of water which frequently is rain from the sky. ...
www.east-frisia.com/html/reports.html

| Book Review | The American Historical Review, 109.3 | The ...
... But at both sides of the canvas a very different, dynamically tilted river comes into view, full of barges, cranes, straightened concrete margins, smoke, and ...
www.historycooperative.org/ journals/ahr/109.3/br_121.html

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Note added at 53 mins (2005-01-13 21:07:01 GMT)
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The link for the first example is:

http://encarta.msn.com/text_761574006___4/Everglades.html


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Note added at 1 day 16 hrs 29 mins (2005-01-15 12:42:48 GMT)
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Here\'s what \"desempenado\" means, according to Houaiss:

n adjetivo
a que se tirou o empeno; não empenado
1 de porte esbelto; airoso, aprumado, elegante
Ex.: figura, estatura d.
2 a que se tirou a aspereza ou a irregularidade do reboco ou estuco; aplainado, liso, plano
Ex.: parede d.
3 livre de empenos e irregularidades (diz-se ger. de peça de madeira)
4 de acordo com a linha de prumo; nivelado
Ex.: muro d.