Prediction of resistance to flow is one of major challenges in river engineering projects. Bedforms exist with different geometric in geravel bed rivers, including pools and riffles. Interaction of flow with bedform play an importet role in many aspects of river engineering studies such as stable chonnle design, river restoration and flood protection. Existing methods to estimate flow resistances in literature have developed for uniform bed and flow, showing considerable overestimation when they apply for the non-uniform bed and flow. The objective of this study is to investigate resistance to flow for four selected reaches in gravel rivers of Seymareh and Chenareh in Ilam with pools as dominant bedforms. At each reach, four cross sections were studied in details. Shear velocity was determined by three metods, the law of wall (the logarithmic law), saint-venant and the boundary layer chara cteristics. The results revealed the boundary lager characteristics method presents the best estimator of shear velocity. The maximum resistance to flow was considred at the top of the pools. The relative sumbmergence displays the highest effect on flow resistance perdition. Due to the bed variation along the rivers a local estimation of resistance to flow is not realistic, calling for more robust methods of prediction over the bed forms. According the double-averaged method was applied for the first time in Iran in this study. Application of this method showed that the log law works well over the bed forms in river, especially for determination of sheer velocity, and resistance to flow. Key words : Flow Resistance, River, Bed Forms, Double-Averaged Method