Abstract submitted for poster presentation at the BYU-Idaho Student Research Conference
Principles of Equilibrium Demonstrated on a Stream Table
Grant Coleman, Loren Wagner, and William W. Little (mentor)
Three fundamental factors control equilibrium in natural fluvial systems: discharge, load, and gradient. A stream naturally modifies its gradient to barely transport sediment entering from tributaries and adjusts its cross-sectional area (width and depth) to barely contain bank full discharge. Changes in any one of
these factors affects behavior of the other two. A stream in equilibrium develops a
graded profile. When equilibrium is disrupted, the stream generates a new graded profile that is either steeper or gentler than the previous as it returns to equilibrium. For example, a drop in base level steepens gradient, increasing discharge velocity, leading to erosion. This, in turn, flattens the gradient and decreases discharge velocity, until the stream is again barely
able to transport the sediment provided to it. Changes in the other factors affect the stream in a similar way. Within a balance between these three factors,
a migrating meandering channel can be created and sustained. Using a stream table with variable base
level, water discharge, and sediment feed capabilities, we have successfully tested and
demonstrated these concepts.
I think you need to focus more on how the variables of equilibrium affect one another than on what we are doing in our experiment.
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