The effect of submerged Pipe diameter on scour controlling a direct laboratory flume was experimentally studied. Experiments were carried out on a cylindrical Pipe with or without a lower blade. For these experiments, four Pipe diameters, four blade lengths, and five horizontal placement modes for the lower blade were considered using a constant discharge under clear-water conditions. At the end of each experiment, the length and depth of scour beneath the Pipe were measured. According to the results, the location of the lower blade and increased Pipe diameter affect the scour depth around the Pipe. In all cases, the use of a longitudinal blade caused an increase in the percentage of scour depth reduction around the submerged Pipe. For a Pipe with a diameter of 3. 1 cm, the use of a blade length of 2. 5 cm downstream the center of the Pipe reduced the scour length by 70% on average as compared to the Pipe without a lower blade.