Design of Stable Riprap Downstream of Stilling Basins Using Froud Number

Local Scour downstream of hydraulic structures is one of the most important factors that may either endanger the stability of the structure or decrease its efficiency. Therefore, estimating the geometry of scour hole and its evolution is one of the main questions which engineers are often faced in designing of hydraulic structure. The present paper is aimed to study the design criteria for stable riprap downstream of stilling basins behind the sluice gates. An experimental study was therefore, conducted and the stability of eight different sizes of riprap were studied under varying flow characteristics. The study was based on dimensional analysis whereby some empirical relationships were concluded and recommended as the design criteria for stable riprap downstream of stilling basins behind sluice gates. The experimental results were also assessed using the recommended methods by Peterka (1968), Pilarczyk, K.W, (1990) Scarameia and May (1992) which showed an acceptable agreement with some of these reports. The research was concluded by recommending a simple formula consisting the whole variables affecting the phenomenon of riprap instability.