How do bedform patterns arise? New views on the role of bedform interactions within a set of boundary conditions

Abstract

One explanation for bedform patterns is self-organization in which the pattern emerges because of interactions among the bedforms themselves. Models, remote images, fi eld studies and lab experiments have identifi ed bedform interactions that involve whole bedforms, only bedform defects, or that are remote interactions between bedforms. It is proposed that bedform interactions form a spectrum from constructive to regenerative in pattern development. Constructive interactions, including merging, lateral linking, cannibalization, and remote transfer of sediment, push the system toward fewer, larger, more widely spaced bedforms. Regenerative interactions, including bedform splitting, defect creation and calving, push the system back toward a more initial state. Other interactions, including off-center collision, defect migration, and bedform and defect repulsion, cause pattern change, but may not be strongly constructive or regenerative. Although bedform interactions are ubiquitous to any fi eld of bedforms, their dynamics, fl ow-fi eld modifi cation, and impact upon measurable pattern parameters are yet poorly understood. Most bedform interactions span bedform types and fl uids, supporting the hypothesis that pattern emerges from dynamics at the bedform level in a hierarchy that includes lower levels of bedform-fl ow and grain-fl uid interactions. Bedform interactions alone, however, cannot account for the rich diversity of bedform patterns in nature. It is proposed that fi eld diversity arises because of boundary conditions, which are the environmental variables within which a fi eld evolves. Conceptually, boundary conditions modify the shape of the attractor toward which a fi eld evolves, possibly by altering the type and frequency of bedform interactions. Boundary conditions are broadly similar within system types, but are unique for each bedform fi eld so that no two are ever exactly alike. Although aeolian and fl uvial systems share some types of boundary conditions, fl ow depth is a unique boundary condition in shallow fl uvial systems.

Source-to-Sink

“…Bedform interactions occur as bedforms or their crestal terminations (defects) approach each other or actually collide. Dune and other bedform interactions have been documented in a range of settings (see review in Kocurek et al [2010]), and pattern emergence and evolution as a function of bedform interactions have been explored in models (e.g., Forrest andHaff 1992, Landry andWerner 1994) and with natural bedforms (e.g., Hersen and Douady 2005, Elbelrhiti et al 2008, Ewing and Kocurek 2010a.…”

Remote sensing and spatial analysis of aeolian sand dunes: A review and outlook

“…Beginning with images from the early 1970s, remote sensing (RS) has revealed a rich diversity of dune field patterns on Earth, Mars, Venus, and Titan. The synoptic perspective provided by remote sensing imagery has, however, only recently stimulated a shift away from the singledune studies popularized in the 1980s and 1990s (Livingstone et al, 2007) towards dune field-scale studies that incorporate spatial analysis (SA) of boundary conditions, dune activity, dune patterns and hierarchies, and dune-dune relations (e.g., Tsoar and Blumberg, 2002;Hugenholtz and Wolfe, 2005a;Kocurek and Ewing, 2005;Mitasova et al, 2005;Ewing et al, 2006;Bishop, 2007;Wilkins and Ford, 2007;Ewing and Kocurek, 2010a,b;Hugenholtz and Barchyn, 2010;Kocurek et al, 2010).…”

“…Advances in computer hardware and software throughout the 1990s facilitated a shift in study to the reflectance characteristics of dune surfaces (Paisley et al, 1991;Lancaster et al, 1992;Tsoar and Karnieli, 1996;Walden and White, 1997;White et al, 1997;Blumberg, 1998;Pease et al, 1999) and innovative approaches for quantifying historical changes in dune activity (Anthonsen et al, 1996;Brown and Arbogast, 1999). In the last decade, additional progress has been made in the quantitative analysis of dune morphodynamics Vermeesch and Drake, 2008;Bourke et al, 2009;Necsoiu et al, 2009) and dune field pattern analysis (Kocurek and Ewing, 2005;Ewing et al, 2006;Bishop, 2007;Wilkins and Ford, 2007;Mason et al, 2008;Bishop, 2010;Ewing and Kocurek, 2010a,b;Hugenholtz and Barchyn, 2010;Kocurek et al, 2010).…”

Simple stochastic cellular automaton model for starved beds and implications about formation of sand topographic features in terms of sand flux

“…Car transportation rates correspond to sand flux for sediment beds, which is a quantifiable factor. In geomorphology and sedimentology, while interconnectional properties among different levels of interaction (for example, grain−fluid, bedform−fluid, and bedform−bedform) have been identified (e.g., Kocurek et al 2010), differences in the grain-flow phase have not been clearly identified.…”