Evaluation of Image Processing Technique in Estimating the Manning's Roughness Coefficient in the Surface Layer of Riverbeds
Author(s):
Abstract:
Considering the importance of adequate roughness coefficient estimation in river engineering studies, evaluation of image processing technique in estimating Mannings roughness coefficient in the surface layer of riverbeds carried out in this study. The mentioned approach evaluation conducted by implementing of sieving analysis and digital image processing methods simultaneously for a 7.5km reach of Shalmanrood River of Gilan. The processing of captured images signifies that this technique has an excellent accuracy in estimating the size of sediment particles (particles with a size of d50 or larger) and can be used to estimate Mannings roughness coefficient of sediment particles of riverbed, utilizing the given empirical formulas. To evaluate the image processing results in estimating Mannings coefficient values, one-dimensional modeling by HEC-RAS Hydraulic model was used and the model was conducted through different scenarios. Finally, on given cross sections, the comparison of output hydraulic properties with respect to Cowans method results showed that Brays empirical formula (d90) will have the best efficiency in estimating the Mannings roughness coefficients in the surface of riverbed, with a maximum relative difference of 13.7% in top width.
Keywords:
Language:
Persian
Published:
Iranian Journal of Soil and Water Research, Volume:47 Issue: 4, 2017
Pages:
711 to 722
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