Author(s): Yongjeon Kim; Jisung Kim; Chanjoo Lee; Won Kim
Keywords: No Keywords
Abstract: In Korea, there are not enough databases for roughness coefficient in the field. For estimating roughness coefficient by the "visual comparison" approach, commonly we used to refer to the foreign pictorial guides, such as Barnes' (1967) or Hicks and Mason's (1998). However, there are some differences between foreign and Korean rivers. Typically, rivers in Korea show very large flow variation during the flood period, and the hydrographs exhibit rapid and short rising limbs with high peaks. The ratio of maximum to minimum discharge usually ranges from 300 to 400. The roughness coefficient associated with discharge also shows very wide range. In this study, roughness coefficients were measured and analyzed for the 13 streams in South Korea by using field data. Variation of roughness coefficient associated with the change of discharge during the summer flood season is calculated by Manning and Energy equations. In this study, roughness coefficient at each site tends to decrease in accordance with increase of discharge. Roughness coefficient values disperse widely as bed material size increases. Limerinos' (1970) formular for roughness estimation is also verified.