Experimental investigation of time-dependent local scour downstream of a stepped channel

Abstract

In this study, temporal variation of local scour occurring at the downstream part of the stepped channel were investigated experimentally. The experimental tests were carried out in a stepped flume with a height of 2.4 m. The width of the rectangular flume was 0.10 m and the length of the stilling basin was 2.12 m. Bed material was placed in a sediment box with a height of 24 cm and length of 2.48 m, without any compaction. Experiments were carried out by using bed material of 4 different grain size distributions, 2 different sill heights and 6 different flow rates. Two empirical equations which include Shields parameter (θ) and densimetric Froude particle number (Fd) were proposed by using the experimental findings to predict the temporal variation of the scour depth. The R2 (coefficient of determination) values were computed for both proposed equations as 0.866 and 0.865. The scatter index (SI) values were also determined and computed as 8.73% and 8.25%. The fit of the equations was also determined by means of Fisher’s test.