Turbulent structures in open-channel flows over a concave bed are analyzed by using a hybrid method that combines a proper orthogonal decomposition (POD) with a multiresolution approximation (MRA). The flows over a shallow concave and a deep one are measured by a particle image velocimetry. At first, the time-series of the velocities are clearly classified into three components by using the MRA, including the fluctuation component due to the organized turbulence in a mixing shear layer between the main-channel and the concave. Then, the POD of the organized turbulence component successfully extracts their characteristics, such as the predominant spatial structures and their temporal interactions, as well as the effect of the concave shape. These results strongly suggest that the present hybrid method is effectively available for detecting the spatiotemporal coherent structures in the flows.