PARAMETER-IDENTIFICATION FOR A RUNOFF MODEL FOR FOREST ROADS

Rainfall simulation is a commonly used approach for studying runoff an d erosion from forest roads, and a method is needed to estimate infilt ration parameters from these experiments. We used two algorithms, the Simplex and Shuffled Complex Evolution, to estimate parameters for a p hysically based infiltration and overland flow model. Each algorithm w as tested by estimating parameters for 92 field-measured hydrographs f rom forest roads. Nine of the field-measured hydrographs allowed us to further test whether estimated parameters could be extended to other antecedent conditions and plot sizes. The results demonstrate (1) the physically based model is able to estimate hydrographs from forest roa ds, (2) the two algorithms find unique parameter sets in spite of an e rror surface that suggests identifiability problems between the hydrau lic conductivity and pressure parameters, (3) the two algorithms conve rged to the same parameter values, and (4) that parameters estimated f or one antecedent condition and plot size can be extended to others wi th reasonably small error.