Field and numerical studies of self-organization in high-order drainage networks

由河流网络形成的熟悉的分支模式是地球表面最广泛的特征之一。然而，这种基于侵蚀力学的分支模式的解释已经被证明是难以捉摸的，因为难以对地球表面的大面积区域进行建模，并且缺乏一个统一的框架来将河流网络的几何形状与基本侵蚀规律联系起来。因此，许多以前的研究河流网络集中在随机或基于规则的模型。该项目将开发一个新的框架，利用侵蚀力学来解释河流网络的分支模式。新的框架是基于这样的原则，即河流网络的形式反映了侵蚀的程度，由切割河流主导侵蚀的岩石和土壤运输山坡上。该研究的两个主要组成部分将是模拟大规模河流网络发展的数值实验，这将提供一种校准新的基于力学的框架的方法，以及在简单地质和构造条件下形成的两种景观的实地研究，这将提供理论预测的独立测试。除了对河流网络的分支结构产生更好的机械解释外，研究结果还将提供一种方法，当侵蚀和沉积物运输的测量不切实际时，以及一种量化降雨率和岩石类型等因素对大面积岩石的影响的方法，河流网络是大陆沉积物、地表水和营养物质的主要通道，其结构对生态系统功能、水资源、农业和碳循环至关重要。这项研究将提高我们对地质、气候和生物等主要因素如何控制河网分支结构的理解。研究结果不仅有助于确定特定河流网络发展的主导条件，还将为河流网络如何应对降雨，植被和其他因素的变化提供信息。通过开发新的计算技术，该项目还将提高其他研究人员模拟地球表面环境变化的能力。

The familiar branching pattern formed by river networks is one of the most widespread features of Earth's surface. Yet explanations for this branching pattern based on erosion mechanics have proven elusive due to the difficulty of modeling large regions of Earth's surface and the lack of a unifying framework for relating the geometry of river networks to basic erosion laws. Consequently, many previous studies of river networks have focused on random or rule-based models. This project will develop a new framework for using erosion mechanics to explain the branching patterns of river networks. The new framework is based on the principle that the form of river networks reflects the degree to which erosion by incising rivers dominates erosion by rock and soil transport on hillslopes. The two main components of the research will be numerical experiments that simulate the development of large-scale river networks, which will provide a means of calibrating the new mechanics-based framework, and field studies of two landscapes that formed under simple geologic and tectonic conditions, which will provide independent tests of the theoretical predictions. In addition to generating an improved mechanistic explanation for the branching structure of river networks, the results of the study will provide a way to infer long-term landscape dynamics from present-day topography when measurements of erosion and sediment transport are impractical, and a way to quantify the influence of factors such as rainfall rate and rock type on the large-scale topography of Earth's surface.River networks are the main conduit for sediment, surface water, and nutrients on the continents, and their structure is critical to ecosystem function, water resources, agriculture, and the carbon cycle. This research will improve our understanding of how major factors such as geology, climate, and biology control the branching structure of river networks. The results will not only help determine the dominant conditions under which a given river network has developed, but will also inform expectations of how river networks will respond to changes in rainfall, vegetation, and other factors. Through the development of new computational techniques, this project will also advance the ability of other researchers to model changes in Earth's surface environment.