资源环境科技发展态势分析平台

How do gravel‐bed pool‐riffle streams adjust to changing upstream water and bedload sediment supplies, and what analysis techniques can help to effectively identify how change occurs? Here, we use a mixture of field and experimental data to examine these problems, and apply a suite of traditional and novel analysis approaches to highlight dynamics which might otherwise go undetected. Eleven years of monitoring channel morphology in a small forested watershed indicate that pool‐riffles persist large changes in upstream water and bedload supply, and that bed architecture relief is correlated to flow magnitude. A flume experiment consisting of eight runs was conducted to examine the field case in more detail. The experimental design split the eight runs into four runs of relatively high water and sediment supply, and the remaining four of relatively low water supply, but with no upstream sediment supply. Experimental results corroborate the field‐based measurements of pool‐riffle persistence, which is due to a coupling between downstream width variations, and spatial patterns of flow velocity and bedload transport. More specifically though, measurements made during the flume experiments along a prominent pool‐riffle pair indicate that temporal and spatial changes to topography, flow hydraulics and bed surface sediment texture are in detail rich, and more nuanced than existing generalizations offer. For example, clustering analysis completed using self‐organizing maps (SOMs) indicates that sediment sorting between pool and riffle is not simply a binary type response of finer vs. coarser described by some characteristic grain size.

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