Floating vegetated islands (FVIs) are extensively implemented in various river ecology restoration projects, given their capability of decontaminating pollutants. The fluid dynamical behaviors of turbulence through FVIs are studied in the flume by using the SonTek Acoustic Doppler Velocimetry. Through conventional spectral and quadrant analyses, flow characteristics, such as energy content and turbulent momentum exchange, are investigated as the flow encountered a series of root canopies. A shear layer with corresponding coherent vortex structures at the bottom of root canopies occurred, which is generated by Kelvin–Helmholtz instabilities. These instabilities are usually derived from velocity differences between root canopy and gap region. Shear- and stem-scale vortices are identified by using spectral analysis. The power spectral density function on measured vertical velocity fluctuations in the flow direction …