Mean Flow and Turbulence Characteristics in Pool-Riffle Structures

Channelization limits the geomorphological and biological diversity of many urban streams. Whenever the existing infrastructure prevents re-alignment of the channel planform, in-channel structures of the pool-riffle type offer an alternative means to provide some degree of variability in the flow pattern. This paper presents mean flow and turbulence measurements obtained on a physical model of pool-riffle structures designed to restore low gradient streams in heavily urbanized areas. The data collected include high-resolution 3D velocities as well as water surface elevations for different flow conditions. The results show that the flow is highly three-dimensional, and that the effect of the structures is more important for low flow conditions. Also, flow patterns resemble that of natural pool-riffle sequences. Implications for sediment transport, bed and bank morphology and aquatic habitat are analyzed.