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Preliminary verification of empirical formulas to define the roughness coefficient
 
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Katedra Inżynierii Wodnej i Geotechniki Uniwersytet Rolniczy w Krakowie
CORRESPONDING AUTHOR
Bogusław Michalec   

Katedra Inżynierii Wodnej i Geotechniki Uniwersytet Rolniczy w Krakowie
Submission date: 2021-01-05
Final revision date: 2021-02-12
Acceptance date: 2021-02-13
Publication date: 2021-03-24
 
Acta Sci. Pol. Formatio Circumiectus 2020;19(4):19–30
 
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ABSTRACT
Aim of the study:
The aim of the study was to carry out a preliminary verification of empirical formulas used to calculate the Maninng’s roughness coefficient. The results of the pilot investigations carried out on the Racławka Stream made it possible to determine the roughness coefficients using the transformed Chézy-Maninng equation, the formula developed from transformed Bernoulli’s equation and the formula in which the drag coefficient was calculated from the Colebrook-White equation.

Material and methods:
On the basis of the calculated coefficients, preliminary verification of the applicability of the formulas developed by Bray, Jarrett, Sauer, Lacey, Riggs, Gessler as well as Dingman and Sharma was made. For this purpose, five cross-sections, marked from 0-0 to 4-4, were marked on the examined section of Racławka. Surveying measurements of cross-sections, channel slope and water-surface slope were made, as well as hydrometric measurements of the water flow velocity were made.

Results and conclusions:
The roughness coefficient calculated by the formula developed from transformed Bernoulli's equation was 0.087, 0.059, 0.049 and 0.044 m-1/3∙s, for the cross-sections from 1-1 to 4-4, respectively. On the other hand, the roughness coefficient calculated for the 0-0 cross-section using the transformed Chézy-Maninng equation and the formula in which the drag coefficient was calculated from the Colebrook-White equation, is 0.041 and 0.045 m-1/3∙s, respectively. The obtained results indicate the possibility of using Lacey and Sauer's empirical formulas to determine the roughness coefficient for streams with morphological and hydraulic characteristics similar to those of the Racławka Stream.

ISSN:1644-0765