Uncertainty analysis of hec-hms model parameters using monte carlo simulation

Rainfall-runoff modelling was carried out to determine Hydrologic Engineering Center's Hydrologic Modeling System model parameters for catchments in Johor, Malaysia. Uncertainty analysis, using Monte Carlo simulation, with a sample trial of 5,000 is then applied to the model parameters based on uniformly distributed samples. Sixteen sub-catchments drawn from Sungai Johor, Sungai Tebrau, Sungai Skudai and Sungai Segamat were selected. The rainfall-runoff modelling gives a mean correlation coefficient of 0.9038 and mean efficiency index of 81.53%, indicating a good prediction. Results from the uncertainty analysis give values in the range of 1.25- 14.99mm for initial loss, with a mean of 8.09 mm. The constant loss rate takes a range of 7.98-299.87mm/h with mean value of 153.55 mm/h. The range of values for imperviousness is between of 0.017% and 44.99% with mean value of 22.47%. Simulation result for time of concentration is in the range of 0.44-14.53 h with mean value of 7.62 h. The storage coefficient takes values from 0.22 h to 5.16 h with mean value of 2.71 h. The outcome of this work quantifies the uncertainty associated with these parameters and the result can be used to narrow down the range at which initial estimates are made during future modelling processes.