Fluvial and Ecological Dynamics of Stream Confluences

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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.