River restoration revolution: evaluation of new, low impact channel designs using physical models

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This project will improve our ability to protect infrastructure and ecological health for urban streams that havebecome unstable due to flow changes. In urban areas, changes to the land surface (combined with theconstruction of storm drains) has fundamentally altered how water moves across the land surface. The samerainstorm in a urban area produces a larger flood than it would in a natural environment, and urban streamsoften become unstable due to the increased flows. In order to control the hazards associated with urbanstreams, it is common practice to design and build a range of structures within the stream in order to limiterosion, particularly when infrastructure such as roads, buildings or buried pipes could be affected. Pastpractices relied on building large rock features and/or concrete structures designed to prevent any movement ofthe stream at all (so-called 'hard engineering" techniques); that is, streams were transformed from anunacceptably unstable state resulting from urbanization to a completely static one where no change to thechannel is possible. The natural, stable state (in which small, localized changes occur on an annual basis) iscompletely by-passed, and as a result, the ecosystems that depend upon these streams suffer. Relativelyrecently, policy makers and land managers have expressed their intention to protect both infrastructure andaquatic ecosystems. The advances made by Dr. Eaton and his research group on the factors controlling channelstability suggest that it is possible to gradually adjust the level of channel activity by adding or removing smallvolumes of the coarsest material naturally found in the stream. This implies that, rather than forcing a stream toremain completely static within the confines of a concrete boundary, it may be possible to modify the sedimentwithin the channel so as to restore the natural level of channel activity, and to prevent the urbanization-inducedinstability that can be costly, both in terms of damage and loss of human life. This grant will allow GEOMorphix Ltd. and UBC to evaluate this promising approach in the context of ongoing restoration activities inthe Greater Toronto Area.