|Maslyn, R. Mark, 2004, Eolian Sand Dunes: Models of Emergent Features in Self-Organizing
Systems (abs) : Am. Assoc. Petrol. Geol., 2004 Rocky Mountain Section Annual Meeting, Abstracts and Programs, p.
"Self-Organizing" is a term applied to dynamic systems of independently acting agents that together produce
coherent behavior. Sand dunes, built one sand grain at a time, are self-organizing features that emerge from simple
rules for sand transport and deposition, applied to a set of initial conditions. Resulting dune types depend on
surprisingly few variables: initial sand concentration (availability). and wind regime (velocity, variability,
and complexity). The author has written a simulation program that incorporates these variables and graphically
displays sand dunes as they are built on a grain by grain basis. Major dune types such as barchanoid, star, and
longitudinal can be created from specific sand concentrations and wind regime values identified by the author.
Published wind regime values for each dune type along with experimentally determined sand availability values were
used as starting points to find the values that best produced each dune type. Intermediate model values resulted
in dunes transitional in form between these types. Since these are real-time simulations, changes in wind regime
values while running the simulation resulted in concurrent changes in dune morphology and orientation. With the
new values, the sand dune areas reorganized into different patterns. There is also evidence that with the simulation
values held constant, sand dune patterns can continue to evolve with time. For example, in several longitudinal
dune simulations, multiple individual sand ridges formed early in the simulation over time began to merge into
fewer but larger longitudinal ridges with the same orientation.
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|Last updated August 11, 2004