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NRCS Velocity Based Method --Divide flow path into segments overland flow shallow concentrated flow
channel flow --Estimate velocity for each segment --Compute travel time for each segment --Sum of the travel times is the time of concentration - - -
NRCS Velocity Based Method1048766 Overland Flow (aka Sheet Flow)whereTt = Travel time hoursn = Manning Manningrsquos roughness coefficient for sheet flows L = flow length feetP2 = 2 2-year 24 24-hour rainfall ins = slope of hydraulic grade line (land
slope) ftft40502800070
channel flow --Estimate velocity for each segment --Compute travel time for each segment --Sum of the travel times is the time of concentration - - -
NRCS Velocity Based Method1048766 Overland Flow (aka Sheet Flow)whereTt = Travel time hoursn = Manning Manningrsquos roughness coefficient for sheet flows L = flow length feetP2 = 2 2-year 24 24-hour rainfall ins = slope of hydraulic grade line (land
slope) ftft40502800070