Critical review of equations to determine theeffect of artificial roughness in a channel withsteep slopes

It is possible in lined channels with a steep slope at the bottom to achieve such high water velocities that it becomes necessary to modify their roughness to decrease the speed. This paper presents the results of a study to determine the confidence degree that could be expected from a criterion developed for the design of artificial roughness at the bottom of lined channels. By applying Buckinghamʹs theorem a review is made of an approach proposed by Zamarin and Fandieiev [3], and dimensionless expressions are proposed for design purposes. The results derived from the calculations are compared against measurements made at an experimental channel and a discussion is presented about the applicability of the results thus obtained.