Collaborative Research: The effects of weathering on bedrock channel erosion and form

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。河道基岩侵蚀是一个基本的过程，管理景观的演变，尚未得到充分评估。 这种侵蚀的速度及其在河道内的位置取决于河流对河床做功的能量、沉积物覆盖的分布以及河道下基岩的类型。 最近的几个模拟研究已经检查了通道横截面和纵向剖面的耦合演变，但基于实地的研究调查基岩通道侵蚀是罕见的。 此外，很少有研究明确考虑风化作用对基岩河道几何形状和长期河道演变的影响。该项目将测试四个假设，重点是评估风化如何影响基岩河道侵蚀：1）基岩沿沿着河道边缘比靠近河道中心风化程度更高; 2）沉积物覆盖下的风化程度不会增强; 3）基岩的磨蚀率随着风化程度的增加而增加; 4）在风化严重的地方，河道横截面宽而浅，随着风化效率的降低，河道横截面变得更窄更深。 这些假设将通过测量河流站点岩石风化的跨河道分布进行测试，河流站点既有易风化岩石（例如，弱砂岩、石灰岩）和耐风化岩石（例如，石英岩，花岗岩）在三个水文气候设置。 风化程度将使用两个地球化学风化指数进行量化，在现场使用施密特锤和裂缝密度和长度，在实验室使用巴西拉伸劈裂试验。 岩石的可蚀性将通过实验室中的研磨实验来测量。 这些调查的结果将使风化作用纳入现有的基岩侵蚀数值模型中。河道对岩石的侵蚀形成了地球上一些最壮观的地形（例如，大峡谷），是最有效的侵蚀过程中活跃的非冰川景观。 因此，了解河流对岩石侵蚀的过程以及这些过程的工作速率对于解释地球表面的历史至关重要。使用现场调查，实验室测量和数值模拟，几个假设将进行测试，有重要意义的记录在不同conditons下的河流渠道基岩侵蚀的性质和速度。该项目将提供大量的教育和人员发展的好处，包括支持undergaraduates，研究生，博士后研究员。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Erosion of bedrock in river channels is a fundamental process governing the evolution of landscapes that has not yet been evaluated fully. The rate of this erosion and its location within a river channel depend on a river's energy available to do work on the river bed, the distribution of sediment cover, and the type of bedrock underlying the channel. Several recent modeling studies have examined the coupled evolution of channel cross-sections and longitudinal profiles, but field-based studies investigating bedrock channel erosion are rare. Moreover, few studies have explicitly considered the effects of weathering on bedrock channel geometry and long-term channel evolution. This project will test four hypotheses focused on evaluating how weathering affects bedrock channel erosion 1) bedrock is more highly weathered along channel margins than near the channel center; 2) the degree of weathering is not enhanced beneath sediment cover; 3) the abrasion rate of bedrock increases as the degree of weathering increases; and 4) where weathering is substantial, channel cross-sections are wide and shallow, and as weathering efficiency decreases, channel cross-sections become narrower and deeper. These hypotheses will be tested by measuring the cross-channel distribution of rock weathering at stream sites with both easily weathered rocks (e.g., weak sandstones, limestone) and weathering-resistant rocks (e.g., quartzite, granite) in three hydro-climatic settings. The degree of weathering will be quantified using two geochemical weathering indices, in situ using Schmidt hammers and fracture density and length, and in the laboratory using Brazilian tension splitting tests. Rock erodability will be gauged via abrasion mill experiments in the laboratory. The results from these investigations will allow weathering to be incorporated into existing numerical models of bedrock erosion.Rock erosion by river channels forms some of the most spectacular topography on Earth (e.g., Grand Canyon), and is the most effective erosion process active in non-glaciated landscapes. Understanding the processes responsible for rock erosion by rivers and the rates at which these processes work is therefore fundamental to interpreting the history of Earth's surface. Using field investigations, laboratory measurements, and numerical modeling, several hypotheses will be tested that have important implications for documenting the nature and rate of bedrock erosion in river channels under various conditons This project will provide substantial educational and personnel development benefits, including support of undergaraduates, a graduate student, and a post-doctoral research fellow.