Hydraulic characteristics of flow in open channels with spur dikes were studied both theoretically and experimentally. Series of laboratory tests and 2-D numerical computations were performed by varying the interval of spur dikes. It was found that the mass and the momentum exchange rates between the main flow region and the spur dike region are influenced by the interval. Especially, momentum transport is much affected by the interval in equilibrium region. For the case in which the interval of spur dikes is nearly equal to the scale of separated eddies from the first spur dike, the eddies move downstream without changing their structure, and consequently the momentum transport in equilibrium region between the main flow and the spur dike region takes a maximum value.