Characterizing Turbulence Structure along Woody Vegetated Banks in Incised Channels: Implications for Stream Restoration

The impacts of urbanization have modified natural watersheds and stream hydraulic, hydrologic, and geomorphic processes that have lead to geomorphic and ecological disturbances in natural stream systems. These alterations have resulted in channel incision and the loss of channel-scale hydraulic characteristics responsible for initiating and maintaining pool-riffle bedforms, which are capable of supporting diverse biological stream ecosystems. Through the use of FLOW-3D, a 3-dimensional computational fluid dynamics model, three scenarios of an urban, incised, and channelized stream were simulated to characterize the turbulent, hydraulic structure during bankfull discharge. The simulations were conducted with trees inhibiting bankfull flow (representing the channel’s current state), trees removed from the channel, and a restoration design using three clusters of the original trees to initiate flow acceleration-deceleration regions. These simulations suggested that hydraulic processes found to initiate and maintain pool-riffle sequences can be restored to impaired urbanized channels for which these processes have been lost. This research can be applied to stream restoration design in hopes to establish less invasive procedures that can promote the development and maintenance of natural stream processes. If the natural processes can be restored to the channel, it is likely the project will have a higher degree of success in the future of the stream system.