Fluvial and Ecological Dynamics of Stream Confluences

一条溪流流入另一条溪流的地方是水系中的重要点。水流的速度和方向以及河床的形状和特征的突然变化改变了溪流的特征，并创造了独特的生态位，某些物种在其中茁壮成长，而另一些物种则被排斥。关于河流汇流的地貌和生态动力学的研究大多是在实验室通过水槽实验或在计算机上使用数学模型进行的。已经进行了一些现场观测，但测量通常仅限于几个变量。该项目将通过对伊利诺伊州中部两条大小大致相同的溪流汇合处的广泛变量进行详细测量，经验地探索地貌和生态过程。这些测量将被用来确定两个汇合溪流不同流速的时间变化如何影响水流、河床形态和泥沙输送之间的相互作用。将使用一套有关生物现象的测量方法来评估栖息地条件，并确定汇流的地貌特征如何影响汇流上下游水生群落的结构和功能。从事实地观察和数据分析的调查小组的一些成员将是由本科生研究体验计划资助的本科生。这一研究项目是一个单一地点的密集案例研究，但在该地点收集的测量结果将对在实验室和理论环境中开发的定性和数学模型进行一致的检验。除了提供这些模型的经验测试外，该项目还将有助于评估在这样的环境中获得详细测量的方法的有效性。本科生加入该项目的研究团队将加强研究，并将为有前途的本科生提供宝贵的经验。

The places where one stream flows into another are important points in stream systems. Abrupt changes in the velocity and direction of water flow and in the shape and character of streambeds alter the character of the streams and create distinctive ecological niches within which certain species thrive and others are repelled. Most research on the geomorphic and ecological dynamics of stream confluences has been conducted in laboratories using flume experiments or on computers using mathematical models. Some field observations have been made, but measurements usually have been limited to a few variables. This project will explore geomorphic and ecological processes empirically by taking detailed measurements of a wide range of variables at the confluence of two streams of roughly equivalent size in central Illinois. These measurements will be used to determine how temporal variations in the different rates of velocity for the two merging streams affect interactions among flows, streambed morphology, and sediment transport. A related set of measurements of biotic phenomena will be used to assess habitat conditions and to determine how geomorphic characteristics of the confluence influence the structure and function of aquatic communities upstream and downstream from the confluence. Some members of the investigative team engaged in field observations and data analysis will be undergraduate students funded through the Research Experiences for Undergraduates program. This research project is an intensive case study at a single site, but the measurements collected at that site will provide a coherent test of qualitative and mathematic models that have been developed in laboratory and theoretical settings. In addition to providing empirical tests of these models, the project also will contribute to evaluation of the efficacy of methods to obtain detailed measurements in settings like this. The addition of the undergraduate students to the project's research team will enhance the study and will provide valuable experience for promising undergraduats.