Physical habitat analysis and design of in-channel structures on a Chicago, IL urban drainage: A stream naturalization design process

In many urban watersheds, physical habitat degradation rather than water quality degradation has reduced fish community abundance and diversity. Engineering methods are needed to restore degraded stream habitat under conditions of modified hydrologic regimes and land-use constraints on channel planform. Habitat improvement can then be considered an essential component of stormwater management programs. We implemented a design methodology, known as stream naturalization, with the Village of Northbrook, Illinois to improve stream habitat as part of a city-center 0.8-km riverwalk development. Habitat improvement focused on design of pool-riffle structures. Pool-riffle structures were proposed because geomorphic/habitat and bioassessment surveys found irregular pool spacing and lack of deep pools greater than a depth of 0.8 m, limited habitat quality and fish abundance. Simulation of the hydraulic performance of the proposed pool-riffle structures was completed using FLOW3D®, a three-dimensional hydrodynamics model. Velocities from simulations provided data to size bed material, ensuring a stable structure while allowing transport of small particles through pools. The model predicted a natural flow field with lateral convergence-divergence rotating cells providing habitat diversity both hydraulically and morphologically. Pool-riffle structures were constructed in the fall 2001 and winter 2002.