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88 SRICOS-EFA Method HEC-18 Method (Gill Database) (Gill Database) 55 55 50 50 Predicted Scour Depth (mm) 45 45 Predicted Scour Depth (mm) 40 40 35 35 30 30 25 25 20 20 15 15 10 10 5 5 0 0 0 5 10 15 20 25 30 35 40 45 50 55 0 5 10 15 20 25 30 35 40 45 50 55 Measured Scour Depth (mm) Measured Scour Depth (mm) Figure 10.7. SRICOS-EFA Method against Gill (1981) Figure 10.8. HEC-18 Method against Gill (1981) Database. Database. 1 1 10.5 REMARKS Vc = 6.19 y 6 D50 3 (10.1) While it would have been preferable to find a number of full-scale case histories, at least the comparison to databases where Vc is the critical velocity of the bed material, m/s; y is obtained primarily on cohesionless soils gave an idea of how the water depth in the upstream flow, m; and D50 is the parti- the SRICOS-EFA Method compares to the HEC-18 Method. cle corresponding to 50% passing by weight, m. Figure 10.7 Note that the comparison is only based on the maximum depth shows the comparison between the uniform contraction scour of scour values and does not involve the scour rate, which is the depth calculated by the SRICOS-EFA Method and the mea- major difference between the current HEC-18 Method and the surements in the database. Figure 10.8 shows the HEC-18 SRICOS-EFA Method. Overall, it was found that the perfor- equation compared with the same database. As shown, the mance of the SRICOS-EFA Method is similar to the HEC-18 SRICOS Method is reasonably good, but the HEC-18 Method Method except for the contraction scour depth where the is severely under predicting. SRICOS-EFA Method is much closer to the measurements.