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

岩石沿河床的运动称为泥沙运移，对于估计河道稳定性至关重要，因此在洪水期间对基础设施和人类生命构成风险。泥沙迁移预测也被用来帮助恢复河流中众多水生物种的数量。尽管泥沙输运很重要，但泥沙输运是出了名的难以预测，该项目将调查河床结构(如岩石排列)的变化如何影响泥沙输运。然后，这些信息将被用来改进泥沙输送预测。通过与艺术家的合作，雕塑将被暂时放置在河流中，作为1)水流障碍(如巨石和木头)，为一系列鱼类物种提供栖息地，以及2)通过雕塑附近张贴的标志和链接到包含关于该项目科学信息和视频的网站的公共宣传装置。泥沙运移预测的误差可以部分地解释为一个共同的假设，即泥沙运动总是发生在给定河流的相同流量量级上。由于河床结构的变化，泥沙运动的开始可能会发生很大的时间变化。这项建议的目标是更好地了解河床结构的这些时间变化，并利用这种了解准确地预测泥沙运动的开始。利用实验室实验和力学理论来确定和量化控制泥沙运动开始变化的河床参数。这一理论将在仪器齐全的河道中使用现场测量进行测试，并可能取代通常随意选择的导致泥沙运动的单一水流等级。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。

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.