The Geomorphologic Unit Hydrograph provides alternative methodology in deriving the Nash model parameters (n and k) without depending upon the effective rainfall and stream runoff records. The sufficient data on Horton's order ratios and stream flow records of higher order stream at silt monitoring station Mynally watershed used to test the viability of the model. Results showed that accurate determination of average stream flow velocity (3.18 m / sec) is pivotal and performs as sole factor reflecting the variations in the effective rainfall and replaces it.