The method of roughness calculation in rectangular concrete channel

Explored roughness variation with water depth in the rectangular concrete channel by flume experiment and thus established quadratic function of water depth and the roughness, the calculated result showed that the roughness increases with depth. Channel wall roughness was obtained and the roughness in other water depth was calculated according to equation. Through error analysis and calculation, in the practical area of engineering, the error of the measured and calculated roughness in rectangular concrete channel was less than 5.0 percent respectively. The method is short-cut and correct which can satisfy the requirement of engineering practice.