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，来自旱地来源的非现场沉积严重影响水质、生态和生态栖息地。局部强烈侵蚀的地区，如细沟和沟壑，往往是土壤流失的主要原因，也是此类景观产沙量的主要来源，这些地貌特征与活跃的迁移坡头密切相关，即发生局部侵蚀和向前推进的河床表面高程的阶跃变化。本研究计划的主要目标是了解实验系统中活跃迁移的坡口的形态动力学，并为这一离散的侵蚀过程开发基于物理的分析表达式。利用专门建造的配有降雨模拟器和准备好的土床的水槽，我们将在试验中确定不受河道宽度限制的高地集中流中的发育和主动迁移的头坎特性，以响应上游泥沙供应。我们将利用这些信息来建立基于修正的射流撞击理论的集中流中土壤流失的预测方程。这项拟议工作的学术价值旨在通过沟壑、作物沟壑和沟壑等典型的高地集中水流中的陡峭生长和迁移，解决土壤侵蚀和土地退化的基本机制。这项拟议工作的更广泛影响旨在为土壤侵蚀预测技术提供必要的补充，以改进流域管理工具并减少我国土壤资源的进一步退化，美国每年的土壤资源成本估计高达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.