Streams in urban and urbanizing watershed are impacted by altered watershed runoff hydrology and sediment yields, floodplain modifications, and constrained channel planform. One morphological response to these urbanization impacts is the degradation of pool-riffle sequences. Pools and riffles are fundamental mesohabitat units where many lotic biota have evolved to occupy preferentially. Restoring self-maintaining pool-riffle structures is essential to the ecological rehabilitation of urban streams when lost. However restoring these structures can be problematic after a stream has been straightened from prior land development, and current civil infrastructure preventing channel re-meandering. Project goals included: 1) developing a conceptual restoration design by applying geomorphic and three-and two-dimensional hydraulic principles, focusing on flow acceleration and deceleration zones to maintain pool-riffle structures in a straight channel, 2) using River2D, a two-dimensional hydrodynamic model as an ecohydraulic tool to design a pilot project on Beaver Creek, Knox County, Tennessee, and 3) constructing the designed project with follow-up preliminary monitoring and assessment. Ecological information was integrated into the design process from pre-construction monitoring of fish communities, and application of the aquatic habitat module in River2D, utilizing habitat suitability curves (velocity, depth, and substrate) for three fish species. River2D also provided estimates on spatially-distributed shear velocities aiding the design process, which were used for examining channel and bank stability, and placement of root wads. Construction of four poolriffle structures on Beaver Creek was completed in March 2012. A geomorphic survey was completed in April 2013, in which the constructed riffle structures have remained stable even with the project site experiencing eight bankfull events. Post-construction monitoring has shown 3 that the unique design for planform-constrained urban channels has promise for increasing hydraulic habitat diversity and improving ecological integrity in these stressed environments.

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