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INSTRUCTOR: Bryan Dick, P.E., PH, M.ASCE
Purpose and Background
This webinar provides an overview of the importance of channel geometry in a variety of physical settings and demonstrates the need for sediment transport and channel dimension as a primary consideration for project success. The long term stability of stream and river restoration projects, as well as many bank stabilization projects, is highly dependent on proper channel cross-sectional area or channel dimension. Traditionally, open channels have been designed to handle large flow events with little consideration given to the more frequent intermediate flow events that move sediment on an annual basis. As more and more stream restoration projects have been implemented, the ingrained mindset of a larger channel being conservative is apparent in many completed projects that are experiencing excess shear stress, inability to handle the sediment load in wider sections and various other symptoms of over-sized channels. Under-sized channels can have problems as well, such as with sediment transport and pattern and bed profile maintenance. Properly sizing the channel and fitting it within the context of the slope and planform is critical for long term project success of stable channels, both in restoration and conventional hydraulic channels.
This webinar is a continuation of an introduction to stream restoration for technical professionals and is organized in a manner that does not require attendance of each webinar in this series. The principles of stable channel form and sediment transport are highlighted in this webinar while providing insights into successes and failures of projects that were largely depended on the channel dimension.
Primary Discussion Topics
- Overview of the principles of stream restoration
- Stable channel form - dynamic equilibrium
- Oversized and under-sized channel
- Problems with biasing to the recurrence interval
- Restoration and traditional conveyance channel considerations
- Lessons learned from case studies of multiple projects
Learning Outcomes / Benefits
- Appreciate how the channel cross section can affect energy and sediment transport
- Develop an awareness of potential bias in channel sizing
- Gain a better understanding of conservative designs may use smaller channel or muti-stage channels
- Become familiar with a need to converge analytical and empirical solutions
- Learn from the lessons of successful and failed project examples
Intended Audience
- Professional Engineers
- Environmental Scientist/ Ecologist
- Geologist and Geographers
- Planning professionals
- Engineers in Training who have a basic understanding of engineering design, bid-document preparation and construction practices
- Students of engineering, geology and environmental disciplines
Webinar Outline
- Overview of geomorphology natural channel stability
- Over-sized channels
- Under-sized channels
- Dealing with uncertainty with multistage designs
- Sediment transport analysis at different scales
- Converging analytical and empirical solutions
- Recurrence interval and channel sizing
- Sediment starved systems
- Many case studies of implemented projects
- Construction challenges- the practical limitations of equipment