Ecologically Sensitive Channel Design for Urban Receivers: Case Studies.
Historically, engineering practice for managing urban runoff in natural watercourses related to the provision of flood and erosion protection, with typically a minimal regard for the existing or potential aquatic habitat. Engineers were concerned with conveying storm runoff in a safe and efficient manner, which would use a minimal amount of “developable” lands. Short and long-term maintenance costs, and accessibility, were also strong guiding principles in the design.
During the 1960's and 1970's aquatic biologists began to examine the impacts of channel alterations on aquatic ecosystems. The knowledge gained, combined with increased public environmental awareness in the late 1980's and 1990's, has led to stricter agency enforcement of environmental protection legislation. Engineers, along with development proponents, have been able to "rethink" their approach to managing urban runoff. No longer is it satisfactory to provide flood and erosion control at the expense of the environment. Rather, the existing and potential aquatic habitat associated with urban receivers has become an elemental design constraint. The fisheries biologist has become a member of the design team, which focuses on maintaining or enhancing aquatic habitat while meeting other water management objectives. This paper focuses on a series of case studies involving the application of eco-restoration to Southern Ontario stream systems. Successes and failures alike are reviewed, based on documented field evidence highlighting potential future design enhancements.
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