Estimation of parameters for flow through rockfill structures is often a problem either in field or laboratory conditions. In this study, estimation methods were investigated to estimate the best hydraulic parameters for a rockfill structure when measurements of discharge, bed slope and head at specific locations within the rockfill are available. Three different calibration methods were used to estimate the hydraulic parameters related to three different laboratory scale rockfills. These methods include: 1) Simple Linear Regression method proposed by Goodwill and Kaliontsiz, 2) Approximate Slope method proposed in this study and 3) Use of automated calibration tools (e.g. PEST software). It was found that proper use of automated calibration tools produces the best results in terms of the overall behaviour of the simulated water surface profiles inside rockfill and the upstream depth. However, Approximate Slope method can give reasonable and acceptable results with less computational complexity. Simple linear regression method showed the poorest performance. Regression problems may also apply to this method especially under conditions of limited number of data.

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