Morphodynamics of Actively Migrating Headcuts in Rills and Gullies

土壤侵蚀仍然是美国和世界范围内土壤退化的主要原因，土壤流失仍然是农业资源可持续管理的关键问题，来自高地来源的场外沉积严重影响水质，生态和生态栖息地。 强烈的，局部的侵蚀，如细沟和冲沟，往往是土壤流失的主要原因和沉积物产量的主要来源，从这样的景观，这些地貌特征是在密切相关的积极迁移headcuts？本研究计划的主要目标是了解实验系统内的主动迁移水头的形态动力学，并为这种离散的侵蚀过程开发基于物理的解析表达式。 使用专门建造的水槽，配备了降雨模拟器和准备好的土壤床，我们将实验定义的特点，发展和积极迁移水头在高地集中流量不受限制的渠道宽度和上游泥沙供应。 我们将利用这些信息，根据修正的射流冲击理论，建立集中流中土壤流失的预测方程。 拟议的工作的智力价值，旨在解决土壤侵蚀和土地退化的基本机制，在高地集中流典型的细沟，作物沟，冲沟的头切增长和迁移。 拟议工作的更广泛影响旨在为改善流域管理工具和减少我国土壤资源的进一步退化所需的土壤侵蚀预测技术提供关键补充，据估计，美国每年的成本高达400亿美元。

Soil erosion remains the principal cause of soil degradation within the U.S. and worldwide, soil loss continues to be a critical concern for the sustainable management of agricultural resources, and off-site sedimentation from upland sources severely affects water quality, ecology, and ecological habitat. Areas of intense, localized erosion, such as rills and gullies, often are the primary cause of soil loss and the dominant source of sediment yield from such landscapes, and these geomorphic features are in close association with actively migrating headcuts?step-changes in bed surface elevation where this localized erosion and headward advance takes place.The primary goal of this research program is to understand the morphodynamics of actively migrating headcuts within experimental systems and to develop physically-based analytic expressions for this discrete erosion process. Using specially-built flumes equipped with rainfall simulators and prepared soil beds, we shall define experimentally the characteristics of developing and actively migrating headcuts in upland concentrated flows unconstrained by channel width and in response to an upstream sediment supply. We shall use this information to develop predictive equations for soil loss in concentrated flows based on modified jet impingement theory. The intellectual merit of the proposed work seeks to address the fundamental mechanics of soil erosion and land degradation by headcut growth and migration in upland concentrated flows typical of rills, crop furrows, and gullies. The broader impacts of the proposed work seeks to provide the critical addition to soil erosion prediction technology necessary to improve watershed management tools and reduce the further degradation of our Nation's soil resources, whose estimated annual costs in the U.S. are as much as $40 billion.