Role of Bedform Interactions and Boundary Conditions in Pattern Development

空气或水下的涟漪和沙丘等床面场形成了地球、火星和其他星球上一些最引人注目的图案。这些模式是如何形成的在很大程度上是未知的。这项研究试图通过检验模式自组织的假设来理解床形模式的发展。具体地说，这项研究探索了床形本身在一组环境边界条件下的相互作用，作为对图案的形成和演变的主要控制。边界条件对每个领域的床型都是不同的，它控制着相互作用的频率和风格，以产生大致相似的模式，但在不同领域的细节上是独特的。这项研究将创建高分辨率的三维数字地图的时间序列，允许史无前例地记录床形地形、床形之间的相互作用，以及跨越一套具有代表性的环境的模式演变，这些环境的边界条件差异很大。该项目使用(1)机载激光雷达探测新墨西哥州白沙的风沙丘田，(2)低空航空摄影以确定内布拉斯加州浅的北洛普河的特征，以及(3)多波束声学测量以解决路易斯安那州南部密西西比河深处的问题。此外，在北娄普河内的实验将包括使用现场水槽来探索在图案形成时对河道宽度的控制。这项研究的结果将为全面理解由于水流、泥沙侵蚀/沉积和地表地形之间的反馈而产生的沙丘和沙丘场的非稳定自组织行为提供必要的定量数据。沙丘和河流中的沙粒输移可以在大小尺度上改变景观。为该项目收集的数据将改善关于地形如何因沙流而在时间和空间上变化的知识；这些过程主要控制地球和其他行星上地形的演变。为这一研究项目开发的方法和技术将推动对地球表面的实时监测，这是记录逐步的环境变化所必需的，而这些信息对于成功管理自然资源至关重要。

Fields of bedforms such as ripples and dunes under air or water form some of the most striking patterns on Earth, Mars and other planets. How these patterns form is largely unknown. This research seeks to understand bedform-pattern development by testing the hypothesis that the patterns self-organize. Specifically, the research explores the interactions of the bedforms themselves within a set of environmental boundary conditions as the prinicpal control on the form and evolution of the patterns. The boundary conditions, which are different for every field of bedforms, control the frequency and style of interactions to yield patterns that are broadly similar, but are unique in their detail from field to field. This research will create time-series of high-resolution, three-dimensional digital maps that allow for unprecedented documentation of bedform topography, interactions among the bedforms, and pattern evolution across a representative suite of environments that differ significantly in their boundary conditions. This project uses (1) air-borne LiDAR to explore the aeolian dune field at White Sands, New Mexico, (2) low-altitude aerial photography to characterize the shallow North Loup River, Nebraska, and (3) multibeam acoustic surveys to resolve the deep Mississippi River, southern Louisiana. In addition, experimentation within the North Loup River will include using a field flume to explore the control of channel width upon pattern formation. Results of this study will provide the quantitative data necessary to fully understand the unsteady, self-organizing behavior of dunes and dune fields that arise as a consequence of the feedbacks between fluid flow, sediment erosion/deposition, and surface topography.The transport of sand in dunes and rivers can modify the landscape at both large and small scales. Data collected for this project will improve the knowledge of how topography changes in time and space as a result of sand movement; these are the proceses that primarily control the evolution of landforms on Earth and other planets. Methodologies and techniques developed for this research project will advance the real-time monitoring of Earth's surface that is necessary to document progressive environmental change, information that is vital for the successful management of natural resources.