Measuring bankfull channel features, bed sediment, and bed load
Georgia State University, Dept. of Geosciences
This activity has benefited from input from faculty educators beyond the author through a review and suggestion process.
This review took place as a part of a faculty professional development workshop where groups of faculty reviewed each others' activities and offered feedback and ideas for improvements. To learn more about the process On the Cutting Edge uses for activity review, see http://serc.carleton.edu/NAGTWorkshops/review.html.
This page first made public: May 2, 2008
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The students gain field experience measuring bankfull channel characteristics in an urban park, and apply their measurements to determine whether the channel is 'adjusted' to its incoming flow regime and sediment flux.
Upper-level/graduate course in geomorphology
Skills and concepts that students must have mastered
Adjustment of fluvial channels, Shields stress, use of Excel
How the activity is situated in the course
This is the 4th in a sequence of exercises for the course.
Content/concepts goals for this activity
The purpose of this exercise is for students to: (1) get hands-on experience determining the bankfull characteristics for a stream channel, (2) measure surface sediments, (3) observe complications in the balance between channel topography, surface sediments, incoming stream and sediment flux, and changes over time, and (4) learn how to measure bed load sediment.
Higher order thinking skills goals for this activity
Application of textbook concepts to a real-world field setting, field skills development, synthesis of channel morphology, adjustment, and surface sediment ideas, graphing skills in Excel.
Other skills goals for this activity
Description of the activity/assignment
This class exercise is an opportunity for students to gain valuable field experiences and develop fieldwork skills. The goal is to have students compare their measurements of a bankfull channel and its bed sediments with theoretical values that might imply whether the channel is 'adjusted' or is out of equilibrium with its setting. This is accomplished by having the students calculate a bankfull Shields stress value and then compare that value with both: (1) a theoretical range of values that might comprise an 'adjusted' condition, and (2) experimental values for the minimal Shields stress required to entrain bed grains of different sizes. They are then to evaluate whether the channel is stable or not.
Designed for a geomorphology course
Determining whether students have met the goals
Point values are assigned to each calculation and short answer question. Moreover, much partial credit is given to those students who demonstrate conceptual understanding of the questions involved.
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