Measuring bankfull channel features, bed sediment, and bed load

Jordan Clayton
Georgia State University, Dept. of Geosciences
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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.

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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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