Understanding a bedload-dominated stream through spreadsheet modeling
The purpose of this exercise is to teach students to "think like a stream" by integrating modeling with field data to understand the nature of adjustments in bedload-dominated fluvial systems. The context is a study of a piedmont alluvial stream - Middle Cottonwood Creek - and its deposits. The exercise should be transportable to other stream systems.
- In the context of fluvial geomorphology, it improves students' ability to understand bedload-dominated stream morphology as the interaction of discharge, slope, load, and load caliber.
- In the context of student growth it teaches multi-parameteric interactions in complex systems. Specifically, it requires "leaps of faith" in model management by changing a second variable after changes in a first variable have upset the model. Such leaps are best accomplished in a team contact with abundant interaction with team members, other classmates, teaching assistant, and instructor.
Context for Use
- This is a single (3-hour) computer-based lab incorporated into a 300-level undergraduate Geomorphology class about two-thirds of the way through the course.
- The course prerequisite is only introductory Physical Geography or Physical Geology; course enrollment averages 40 (2 20-student labs) including engineers, education majors, soil scientists, geographers and geologists.
- This is the third in a series of Excel spreadsheet models. It continues development of skills with Excel (thus would not necessarily be a good first spreadsheet activity) including conditional expressions and relative and absolute cell references.
- The format is a field data collection exercise and a subsequent modeling exercise, in which the output of the model is constrained by the field data. The desired outcome is an applied understanding of the interaction among stream discharge and slope (stream power) and sediment load and load caliber (bedload).
- The activity includes links to a "virtual field trip" of maps and photographs of Middle Cottonwood Creek (draining part of the west flank of the Bridger Range north of Bozeman, MT) between the Bridger Range and the point where it disappears into subdivisions and agricultural fields on the floodplain of the East Gallatin River. Data from several traverses of the creek is included in the field trip and students use an Excel spreadsheet model to analyze the data.
- This exercise is a computer lab exercise requiring a minimum of three hours of direct instructor oversight. Some teams may require three or more additional hours for completion.