Collaborative Research: Beyond lithologic control of bedrock valley width: Investigating the role of persistent valley cover in bedrock valley width development, Buffalo River, AR

河流通过切割深深的峡谷和雕刻宽窄的山谷来塑造风景，决定着人们的居住地和洪水的去向。人们很少知道河流如何、何时以及为什么在流经景观时切割出宽和窄的山谷，在这些景观中，它们可以“触摸”到毗邻的谷壁。在这个项目中，科学家们将调查对美国第一条国家河流--阿肯色州西北部的布法罗河--开发基岩山谷的控制。这项研究代表着推进对河流及其山谷如何响应和演变的理解的重要一步。了解基岩峡谷如何以及为什么变宽，将使研究人员、土地利用规划者和环境科学家能够解释过去、现在和未来的河流系统如何应对河流泥沙或流量的变化。此外，该项目的科学家将与堪萨斯州和阿肯色州的不同群体的教师和K-12岁的学生互动，并开发一种交互式地图工具，突出地点(布法罗河)和面孔(过去几千年来生活在布法罗分水岭的不同民族)的交叉点。尽管软基岩导致宽阔山谷和坚硬基岩狭窄山谷的直观概念模型，但新的研究表明，基岩山谷宽度开发的两个末端成员在决定基岩山谷宽度和加宽率方面与基岩岩性一样重要。在该项目中，PI将研究基岩谷宽度、加宽率和相关的谷底形态如何受坍塌谷壁材料的持久性和流动性的控制。阿肯色州西北部的布法罗河是一个理想的野外选址，因为不同的岩性创造了宽的和窄的基岩山谷。该项目的目标是1)调查作为坍塌基岩墙体材料块体大小的函数的谷底覆盖物的持久性，以及2)通过利用山谷和渠道形态以及基岩性质的现场测量数据来表征基岩谷壁中的裂缝间距，来确定对坍塌材料块体大小的控制。该项目的最终目标是3)进行一系列水槽实验，以量化山谷加宽末端成员如何控制山谷加宽率、总山谷宽度以及山谷对关键驱动因素变化的响应。在该项目期间收集的数据将允许重新评估现有的基岩山谷加宽理论，并促进对基岩山谷演变的基于过程的理解，以应对外部气候驱动因素。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Rivers shape landscapes by incising deep canyons and carving both wide and narrow valleys, determining where people live and where floodwaters go. Little is known about how, when, and why rivers carve wide vs. narrow valleys as they flow through landscapes where they can ‘touch’ the adjoining valley walls. For this project, the scientists will investigate controls on the development bedrock valleys on America’s first National River, the Buffalo in northwest Arkansas. This research represents an important step in advancing understanding of how rivers and their valleys respond and evolve. Understanding the how and why bedrock valleys widen will allow researchers, land use planners, and environmental scientists to interpret how river systems in the past, present, and future have and will respond to changes in river sediment or discharge. Additionally, the project scientists will engage with a diverse population of teachers and K-12 students in Kansas and Arkansas and develop an interactive mapping tool that highlights the intersection of places (the Buffalo River) and faces (the diverse peoples living in the Buffalo watershed over the past several millennia).Despite the intuitive conceptual model that soft bedrock makes for wide valleys and hard bedrock narrower valleys, new research suggests that two end members of bedrock valley width development are as important as bedrock lithology in determining bedrock valley width and widening rates. In the project, the PIs will study how bedrock valley width, widening rates, and associated valley bottom morphology are controlled by the persistence vs. mobility of collapsed valley wall material. The Buffalo River in northwest Arkansas is an ideal field site given the distinct lithologies that create both wide and narrow bedrock valleys. The project goals are 1) investigate the persistence of valley bottom cover as a function of the block sizes of collapsed bedrock wall material and 2) determine controls on the block size of collapsed material by characterizing fracture spacing in bedrock valley walls, using data from field measurements of valley and channel morphology and bedrock properties. The final goal of this project is 3) conduct a series of flume experiments to quantify how valley widening end members control valley widening rate, total valley width, and valley response to changes in key drivers. The data collected during this project will allow for re-evaluation of existing theories of bedrock valley widening and the advancement of processed-based understanding of bedrock valley evolution in response to external climate drivers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.