Determining the Roughness Coefficient of Natural Channels and Flood Zone Focusing on the Vegetation Effect
Mohammad Hossein Farhangi, Seyyed Danial Hosseini, Seyyed Mohammad Reza Alavi Moghaddam
According to this fact that the subject matter of open channels hydraulic is investigating the rivers streams and one of the effective issues of streams in open channel is resistance against current; therefore, this resistance factor, in the hydraulics of open channels, is considered by applying the channel roughness coefficient. Of the important factors in line with determining this coefficient is the effect of vegetation that has been investigated in this research. By means of available formulas and field visits from the studied area (part of the Kashfrud River), also by means of soil gradation experiment, the exact values of roughness coefficients were determined. Then based on the obtained roughness coefficients, the values of the river flood zone were calculated and compared with the numerical values of the river flood zone which were obtained from Kavosh Pay Mashhad consulting engineers Company information. Different methods have been used to calculate the roughness that based on the obtained results, the area of the river flood zone is different about -29 and +21 percent with the designated values by the consultant. So this difference indicates the importance of this issue. In fact, the issue of scrutinizing the estimation of roughness caused by vegetation on a practical scale should be studied more prudently and with indigenous research on different plant species of each study area.