Doctoral Dissertation Research: Field Investigation of the Influence of Surface Moisture on the Initiation of Motion in Wind-Blown Sand Transport on Beaches

风沙运动是将沙子从海滩输送到沙丘的主要机制。因此，它代表了连接这些地方并控制沿海沙丘发展的一系列相互作用中的关键联系。一个关键的不确定性在于确定阈值条件，即开始输送的风能水平。如果不准确地表示这一阈值，就不可能确定给定的风事件是否会产生运输。这种情况阻碍了风成沉积物预算的中尺度建模，因为目前不可能可靠地预测运输事件的发生。这个博士论文研究项目的目标是验证和校准一个新的模型的阈值条件，在海滩上的风吹运输。这一努力不同于以往的方法，包括一个新的术语，占的范围内的粒度存在于沉积床。根据对之前发布的数据的检查，新模型提供了显着改进的预测能力。此外，该模型还封装了表面水分对阈值条件的影响，这是许多海滩上的一个关键复杂因素。将在两个地点（得克萨斯州帕德雷岛和佛罗里达州圣布拉斯角）进行田间试验，以验证模型。 风速和表面水分含量将在运输事件开始之前进行监测。移动的监测站将安装在海滩不同含水量的位置，每个监测站都包括一个三维声波风速计和一组基于麦克风的跃移探测器。风速计和跃移探测器将被真实的记录，表面湿度测量将使用为此目的设计的手持光学设备进行。在实地研究过程中记录的数据将允许验证和校准的model.This研究代表了一个显着偏离目前的理论框架，用于解释和模拟风沙运输。结果将提供更好的了解沙滩上的沙子的运输，如果所提出的模型成功验证，这项研究将显着提高预测能力。这反过来又将改进对大规模沉积物预算的计算，为研究人员和沿海管理人员提供更准确的估计，说明有多少沙子从海滩移到沙丘，以及何时和在何种条件下可能发生这种情况。例如，这将有助于建立风暴后沙丘恢复的模型，并预测沙丘重建和重建方案所需的时间。最后，这项研究将解决一个最有问题的因素，使风吹沙运输在海滩上：经常存在的表面水分，可以抑制甚至完全阻止沙子的运动风。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立的研究生涯。

The movement of sand by wind is the primary mechanism responsible for delivering sand from beach to dune. As such, it represents a critical linkage in the suite of interactions that connect these places and that control coastal dune development. A key uncertainty lies in the identification of the threshold condition, that is, the wind energy level at which transport begins. Without accurate representation of this threshold, it is not possible to determine whether a given wind event will generate transport. This situation hampers intermediate-scale modeling of aeolian sediment budgets, as it is not currently possible to reliably predict the occurrence of transport events. The goal of this doctoral dissertation research project is to validate and calibrate a new model of the threshold condition for windblown transport on beaches. This effort differs from previous approaches in the inclusion of a new term that accounts for the range of grain sizes present in the sediment bed. The new model provides significantly improved predictive capabilities, based on examination of previously published data. Further, the model also encapsulates the effect of surface moisture on the threshold condition, a key complicating factor on many beaches. Field experiments will be conducted at two locations (Padre Island, TX, and Cape San Blas, FL) to verify the model. Wind velocity and surface moisture contents will be monitored leading up to the start of transport events. Mobile stations, each comprised of a 3-D sonic anemometer and an array of microphone-based saltation detectors, will be installed on the beach at locations of various moisture contents. The anemometers and saltation detectors will be logged in real time, and surface moisture measurements will be conducted using a handheld optical device designed for this purpose. The data recorded during the field study will allow validation and calibration of the model.This study represents a significant departure from the current theoretical framework that is used to explain and model windblown sand transport. The results will provide improved insight into the transport of sand on beaches, and if the proposed model is successfully validated this study will significantly advance predictive capabilities. This will in turn improve calculations of larger-scale sediment budgets by providing researchers and coastal managers with more accurate estimates regarding how much sand is transported from beach to dune, and when and under what conditions such events can occur. This will contribute to modeling of post-storm dune recovery, for example, and for predicting the time required for dune re-establishment and reconstruction programs. Finally, this study will address one of the most problematic factors complicating wind blown sand transport on beaches: the frequent presence of surface moisture which can inhibit or even completely prevent the movement of sand by wind. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.