• Scour Depth
• Rock Sill
• Pile Position
• Flip Bucket
• Enlarged Channel
• Block Ramp

The natural evolution of mountainous rivers makes the study of river restoration necessary. Traditional hydraulics structures like check dams and concrete sills were generally used to control the natural phenomenon of erosion. Check dams and concrete sills are valid restoration structures but they are not suitable for perfect ecological balance because they are usually made of concrete and create an obstacle for fish fauna. Due to this problem the classical hydraulic structures are replaced by the block ramp. Block ramps are artificial reef with a low environmental impact which preserves the ecological characteristics and morphological continuity of the bed. They are realized with big stones, with a regular or with a rip-rap configuration. The characteristic parameters which affect a ramp project are bed material, slope and height, geometric configuration and presence of macro roughness elements. Due to the formation of a hydraulic jump downstream of a block ramp, energy dissipation takes place in the hydraulic jump and scour is formed on the stilling basin downstream of the block ramp. The scour mechanism downstream of a block ramp is greatly influenced by the hydraulic jump formation. In some cases, especially for low slopes and low densimetric Froude number, scour eventually does not occur. In the present work attempt has been made to reduce the scour downstream of block ramps. As it is clear that a thorough study of the scour geometry downstream of a block ramp is very important for safety reasons and is necessary for design purpose of the block ramps. Firstly the scour depth and length downstream of block ramp using a structure similar to a flip bucket was studied. The scour depth and length for Flip Bucket configuration was compared with scour depth in case of no bucket configuration. Secondly the scour depth and length by changing the Pile Heights at the toe of the ramp was investigated. The scour profile was studied very carefully. The effect of the size of the ramp bed material was also investigated. Thirdly the scour phenomenon downstream of a block ramp by introducing protection structures (rock sills) in the stilling basin in case of an enlarged channel is investigated. The scour mechanism and scour geometry was analyzed in presence of protection structures in the form of rocks. The rocks were placed at different locations to analyze its effects on the scour process. Two different channel expansion ratios were systematically analyzed. The type of scour formed were investigated and classified according to the scour morphology and geometry. From close observation it was seen that the introduction of flip bucket, elevated pile height at the toe of the ramp and rock sills in the stilling basin influences the scour profile, in fact scour gets reduced. Relationships were proposed to foresee the scour depth and length in presence of these new changed configurations.