A mechanistic and predictive understanding of temporal variations in the onset of sediment motion

岩石沿着河床的运动，称为泥沙输运，对于评估河道稳定性以及洪水期间基础设施和人类生命的风险至关重要。 泥沙输运预测也被用来帮助恢复河流中的许多水生物种。尽管泥沙输运很重要，但众所周知，泥沙输运很难预测，本项目将研究河床结构（例如岩石排列）的变化如何影响泥沙输运。这些资料将用于改进沉积物迁移预测。通过与艺术家的合作，雕塑将暂时放置在河流中，作为1）流动障碍物（例如巨石和木材），为一系列鱼类提供栖息地，2）通过在雕塑附近张贴的标志进行公共宣传，并链接到包含有关该项目科学的信息和视频的网站。泥沙输移预测中的误差可以部分地由一个共同的假设来解释，即在给定的河流中泥沙运动的开始总是发生在相同的流量量级。由于河床结构的变化，泥沙运动的起始时间可能发生很大的变化。本建议的目标是更好地了解这些床结构的时间变化，并利用这种理解来准确地预测泥沙运动的开始。 实验室实验和机械理论被用来识别和量化的河床参数，控制泥沙运动的开始变化。 这一理论将在一个装备良好的渠道中使用现场测量进行测试，并可能取代导致泥沙运动开始的单一流量大小的任意选择。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The movement of rocks along river beds, called sediment transport, is essential for estimating river channel stability and therefore risks to infrastructure and human lives during floods. Sediment transport predictions are also used to help restore rivers for numerous aquatic species. Despite its importance, sediment transport is notoriously difficult to predict, and this project will investigate how changes in river bed structure (e.g. rock arrangement) influences sediment transport. Such information will then be used to improve sediment transport predictions. Through a collaboration with artists, sculptures will be temporarily placed in rivers to serve as 1) flow obstructions (e.g. boulders and wood) that provide habitat for a range of fish species, and 2) public outreach installations through signs posted near the sculptures with links to websites containing information and videos about the science of this project. Errors in sediment transport predictions can be partly explained by the common assumption that the onset of sediment motion always occurs at the same flow magnitude in a given river. Large temporal changes in the onset of sediment motion can occur because of variations in the channel bed structure. The goals of this proposal are to better understand these temporal changes in bed structure and to use this understanding to accurately predict the onset of sediment motion. Laboratory experiments and a mechanistic theory are used to identify and quantify the channel bed parameters that control variations in the onset of sediment motion. This theory will be tested using field measurements in a well instrumented channel and could replace the often arbitrary choice of a single flow magnitude that causes the start of sediment movement.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.