Collaborative Research: Unlocking The Seismic Signature Of Rivers

河流中砂砾和鹅卵石的搬运控制着河道的变化，因此对地貌学家和河流工程学家具有重要意义。估计河床输沙率最常用的方法是基于水槽实验的经验校准关系。然而，很难评估这种关系如何有效地预测大河极端事件期间的输送率，因为对河床输送的定量测量是劳动密集型的，而且在大流量时，往往是危险的。由于后勤方面的原因，大多数河床研究都是在小山间溪流中进行的。粒子对河床的冲击传递动量，动量反过来又产生弹性（地震波）。因此，地震学（研究地球上的弹性波）可以潜在地限制河流中的河床输运率。我们将利用一个设备齐全的集水区，该集水区对泥沙在河道中移动的时间和速度有独立的限制，部署一系列地震仪，以测试在搬运过程中河床泥沙与河床碰撞产生地震波的理论预测。更清楚地了解粗沉积物在河道中的移动时间和速度，对于规划河流内和河流附近的基础设施（如桥梁、水坝、道路）至关重要。预测粗沙输运的方法通常是在受控环境下开发的，在大洪水中可能不准确，而预测泥沙运动是最关键的。利用现有科学（地震学）的新应用，我们正在开发一种不需要在河流中部署任何仪器就可以测量大河中河床输运的方法。这项工作有可能大大提高我们廉价、安全和有效地监测河流中沉积物运动的能力，同时促进对河流中影响河床输运率的过程的理解。此外，该项目将有一个外联部分，其中一个本科地质学班将使用这里开发的方法进行沉积物运输监测练习。

Gravel and cobble transport by rivers governs channel change, and is therefore of great importance to geomorphologists and river engineers. The most commonly used approaches to estimating bedload transport rates are empirically calibrated relationships based on flume experiments. However, it is difficult to assess how effectively such relationships predict transport rates during extreme events in large rivers because quantitative measures of bedload transport are labor intensive and, at high flows, often dangerous to obtain. For logistical reasons, most bedload studies have been carried out in small mountain streams. Particle impacts on the river bed transfer momentum, which in turn generates elastic (seismic) waves. Therefore, seismology (the study of elastic waves in the Earth) can potentially constrain bedload transport rates in rivers. Taking advantage of a well-instrumented catchment with independent constraints on when and at what rate sediment moves in the channel, we will deploy an array of seismometers to test theoretical predictions for the generation of seismic waves from bedload sediment impacts with the bed during transport. Understanding more clearly when and at what rate coarse sediment moves in river channels is essential for planning infrastructure in and adjacent to rivers (e.g., bridges, dams, roads). Approaches to predicting coarse sediment transport are typically developed in controlled settings and can be inaccurate in large floods, when it is most critical to be able to predict sediment movement. Using a novel application of an existing science (seismology), we are developing an approach to measuring bedload transport in large rivers without requiring the deployment of any instrumentation in the river. This work has the potential to greatly improve our capacity to cheaply, safely, and efficiently monitor sediment movement in rivers while simultaneously advancing understanding of the processes influencing bedload transport rates in rivers. Additionally, this project will have an outreach component in which an undergraduate geology class will conduct a sediment transport monitoring exercise using the approach developed here.