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Channelization is the alteration of streams and rivers usually by deepening and straightening an existing stream channel or creating a new channel to facilitate movement of water (Armantrout 1998) off land and roads, above and beyond the natural capacity. This includes removal of woody structure, as well as the artificial containment of rivers and streams to restrict the natural movement of the channel. While effective locally in removing water quickly, constructed channels can lead to increased water velocities and flooding downstream. A constructed channel also results in removal of streamside vegetation, disturbance of the natural stream bottom, increased sediment and thermal loading, and additional water quality degradation. The result of these activities is loss of both terrestrial and aquatic habitat and a corresponding loss of species diversity.
The traditional drainage channel design of a trapezoidal cross-section has proven to be inefficient because of its tendency to aggrade (fill in) and increase sedimentation (Schwab et al. 1993). As a result, an improperly designed drainage channel requires repeated maintenance to retain function. Drain construction should incorporate natural channel processes (Rosgen 1996) by allowing streams to efficiently manage sediment and flow and by integrating dedicated areas for water storage, such as created wetlands or ponds.
Conservation Needs to Address Channelization Threats:
Land, Water & Species Management
- Review alternatives prior to the construction of new drains
- Incorporate natural stream channel stability in engineered drainage channels, mimicking natural channel dimension, pattern and profile
- Preserve natural stream structure and function to promote healthy aquatic and terrestrial environments
- Use existing wetland areas near natural drainage courses to provide flood control
Law & Policy
- Follow existing best management practices for channelization
- Provide opportunities for local planning authorities to influence drain code decisions and activities
Research, Surveys & Monitoring
- Conduct research to identify alternatives to current drainage practices
- Test engineered drainage channel designs for their ability to maintain ecological function