Www.wsdot.wa.gov

S K C I A Q m n SR : Rainfall Coefficients HYDROLOGY BY RATIONAL FORMULA (English or Metric Units) m & n = Rainfall coefficients C = Runoff coefficient Kc Kc = Conversion factor (1 for English, 360 for Metric) Tc L = Length of drainage basin (ft or m) Tc = time of concentration (min) A = Drainage area (acres or ha) K = Ground cover coeeficient ... ................
................