CHARACTERISTIC OF ROUGHNESS COEFFICIENT ASSOCIATED WITH DISCHARGE IN GRAVEL-BED RIVER
The purpose of this study is to analyze the characteristics of Mannings roughness coefficient according to change of discharge by using observed data obtained from a stable gravel-bed river and to investigate the applicability of the relevant existing empirical methods to it. Observed water level and discharge data are used as input data for the USGS computer program NCALC model for calculation of the roughness coefficient in total flow regime. Calculated values are compared with roughness values which are estimated with four widely used methods, such as Cowans method, strickler type formulae, power formulae, and semi-logarithmic formulae. The results show that though the empirical methods are able to give similar roughness values only for flood flow, they seem to have rather high uncertainty because of necessity of subjective judgment and differences of resultant values. Roughness coefficients for normal-low flow cannot be estimated from the existing empirical formulae. Especially, using the Manning equation for calculating them should be careful as this provides a wide range of estimated values in normal-low flow. The relations between the roughness coefficient and characteristic size of bed materials are different from them in flood flow even though they have a close relation.
roughness coefficient gravel bed river field data relative roughness
Jisung Kim Won Kim Chanjoo Lee Yong Jeon Kim
KICT, 2311, Daewha-dong, Goyang, Gyunggi-do, 411-712, Korea Korea Institute of Construction Technology
国际会议
第16届亚太地区国际水利学大会暨第3届水工水力学国际研讨会(16th IAHR-APD Congress and 3rd Symoposium of IAHR-ISHS)
南京
英文
963-968
2008-10-20（万方平台首次上网日期，不代表论文的发表时间）