The Kirpich Method

For channel-flow component of runoff, the Kirpich equation is:
EquationObject2334
Equation 4-15.
Where:
  • t
    ch
     = the time of concentration, in minutes
  • K
     = a units conversion coefficient, in which K = 0.0078 for traditional units and K = 0.0195 for SI units
  • L
     = the channel flow length, in feet or meters as dictated by K
  • S
     = the dimensionless main-channel slope
If it is determined that a low slope condition or a transitional slope condition exists, the user should consider using an adjusted slope in calculating the time of concentration. See Time of Concentration.