Drainage Design Manual - the City of San Luis Obispo

TABLE 5-1Permissible Velocities For Natural MaterialSoil TypesFine Sand (noncolloidal)Sandy Loam (noncolloidal)Silt Loam (noncolloidal)Ordinary Firm LoamFine GravelStiff Clay (very colloidal)Graded, Loam to Cobbles (noncolloidal)Alluvial Silts (noncolloidal)Alluvial Silts (colloidal)Coarse Gravel (noncolloidal)Cobbles and ShinglesShales and Hard PansPermissible Velocity (meters/second)0.8 (3 ft./second)0.8 (3 ft./second)0.2 (1 ft./second)1.0 (3 ft./second)1.5 (5 ft./ second)1.5 (5 ft./ second)1.5 (5 ft./ second)1.0 (3 ft./second)1.5 (5 ft./ second)1.8 (6 ft./second)1.7 (5.5 ft./second)1.8 (6 ft./second)REDUCTION IN PERMISSIBLE VELOCITY BASED ON SINUOSITYPercent Reduction inSinuosityPermissible VelocitySource: American Society of CivilEngineers, 1985.Slight (1.0 to 1.2) 5%Moderate (1.2 to 1.5) 13%Very Sinuous (1.5 and greater) 22%*Sinuosity - degree of curvature of channelL’LSLO Creek Drainage Design Manual 47 February 2003