PHYSICAL MODELS IN GEOMORPHOLOGY EDUCATION: LESSONS FROM THE STREAM TABLE

Physical processes governing river systems involve complex interactions of various hydro-geomorphic factors that are spatially and temporally variable, and often difficult to observe in situ. By allowing for the control and manipulation of multiple variables, physical models provide the ability to observe complex geomorphic processes, which is not only advantageous for research but also for education. We use a 1m x 2m stream table located at the University of Minnesota, Duluth as an inexpensive and effective tool in enhancing undergraduate education in geomorphology. The stream table has multiple spigots, which allow students to run two experiments simultaneously side-by-side. Students can adjust slope, discharge, sediment supply, grain size, and base level. In a one-week lab, students are asked to propose a research question, design an experimental approach using multiple variables, and carry out an experiment. Because materials are limited, pre-experiment preparation encourages students to be resourceful in their approach.

By varying grain size, water and sediment discharge, and slope, students can visualize the effects of flood frequency, sediment load, or topography on channel morphology. Students also observe morphologic evolution of fluvial landforms, exploring the differences between braided, anastomosing and incised meandering channels. Some of the more creative questions our students have explored include how rivers flow over layered strata, how rivers respond to uplifting anticlines, and how large woody debris affects channel dynamics. These experiments can be performed with easily accessible and inexpensive materials. Often included in the lab is a period of base level rise and fall in the downstream ocean so that students can visualize submerged deltas followed by delta expansion and growth. Monopoly houses work well as “trackers”, with students cheering for their own personal house to last as long as possible.

We recently constructed a much larger stream table (1.5m x 5m) and are exploring how best to utilize it for an upper-level fluvial geomorphology course to allow students to visualize braided systems, track the evolution of the system with the introduction of vegetation, and assist with on-going experiments on suspended sediment trapping efficiency.