RAPID: In-Channel Alluvial Benches and Their Environmental Controls

河道内冲积阶地是位于河床上方但低于主河漫滩表面的河流沉积物的陆棚状沉积。它们的位置和形态可能会使平滩水位的确定变得复杂，因此对河流修复计划至关重要。它们的存在可以影响水力和河岸生境的质量，而它们的质量预算是河流动力学的重要指标。本研究的重点是测量修改旧的渠道长凳记录基尔帕特里克和巴恩斯在1964年在美国东南部的南部皮埃蒙特，和年轻的长凳，可能起源于干旱条件下发生在皮埃蒙特在过去的十年。其他地方的研究人员发现，长凳可能会在干旱期间产生，并在潮湿，洪水为主的政权期间被摧毁。因此，2009年降雨量恢复到过去十年大部分时间的较高水平，有可能启动阶地的快速转变，影响整个区域的沉积物收支和河岸生境。或者，土地利用的历史可能会推翻洪水制度的主要控制台阶的形成和破坏。该项目旨在区分阶地质量平衡的控制，以阐明阶地动态皮埃蒙特流使用测量，地形测年技术，洪水数据分析和土地利用变化评估。该项目具有时间敏感性，因为2009年迄今为止的降雨量远远大于皮埃蒙特南部过去十年大部分时间的降雨量。最近的气象从干旱到潮湿的条件下的过渡提供了一个无与伦比的机会，记录可能已经创建在十年干旱的通道长凳，并观察过渡到更高的流量制度在其开始的影响。这项研究有助于更好地了解河流中的泥沙储存，因为对河道内冲积阶地作为泥沙储存特征的形成和持续性知之甚少。对冲积阶地的了解来自于在气候与美国东部温带气候显著不同的地区进行的研究。因此，这项研究将解决我们目前对以前研究中的长凳的理解是否普遍适用于不同气候环境中的系统。本研究计画探讨特定类型河流沉积物储存特徴的发生、形成与持续性。因此，它将导致更好地了解导致河道沉积物储存的原因，过程和条件，这具有相当大的潜力，有助于使沉积物预算更精确和有意义的了解河流中的沉积物动力学。从应用河流地貌学的角度来看，这项研究将提供新的见解，通过检查位于洪泛平原或主要山谷平坦的水文意义下的地貌表面，确定岸满阶段。最后，这项研究将提供新的见解景观和大气现象的耦合，通过研究干旱的潜在影响与更常见的河流沉积物动力学变化的煽动者，如历史上改变土地利用/覆盖和地表水文。研究结果将在会议报告和研究期刊上广泛传播。

In-channel alluvial benches are shelf-like deposits of river sediment that are located above the channel bed but below the main floodplain surface. Their positions and morphologies may complicate routine determinations of bankfull stage, so vitally important to stream restoration plans. Their presence can impact the quality of hydraulic and riparian habitat, while their mass budgets are important indicators of fluvial dynamics. This research focuses on measuring modifications of old in-channel benches documented by Kilpatrick and Barnes in 1964 in the Southern Piedmont of the southeastern United States, and of younger benches that may have originated during drought conditions occurring in the Piedmont over the last decade. Researchers elsewhere have found that benches may be produced during drought and destroyed during wetter, flood dominated regimes. The return to higher rainfall in 2009 relative to most of the last decade thus has the potential to initiate rapid transformation of benches, affecting sediment budgets and riparian habitat throughout the region. Alternatively, land use history may override flood regimes as the dominant control on bench formation and destruction. This project seeks to differentiate controls on bench mass balance to elucidate bench dynamics in Piedmont streams using surveying, landform dating techniques, flood data analysis and land use change assessment. This project is time sensitive because year 2009 rainfall to date has been much greater than that occurring annually for most of the last decade in the southern Piedmont. This recent meteorological transition from drought to wetter conditions presents an unparalleled opportunity to document in-channel benches that may have been created during decadal drought and to observe the effects of a transition to higher stream-flow regime at its beginning. This research contributes to better understanding about sediment storage in rivers, as not much is known about the formation and persistence of in-channel alluvial benches as sediment storage features. What is known about alluvial benches comes from studies conducted in locations with climates significantly different from those of the temperate Eastern United States. Thus, this research will address whether our current understanding of benches from previous research is generally applicable to systems in diverse climatic settings. This research project examines the occurrence, formation, and persistence of a specific type of river sediment storage feature. As such, it will result in a better understanding of causes, processes, and conditions leading to in-channel sediment storage, which has considerable potential to help make sediment budgets more precise and meaningful in terms of understanding sediment dynamics in rivers. From an applied fluvial geomorphology perspective, this research will provide new insight into the field determination of bankfull stage, by examining geomorphic surfaces located below the floodplain or main valley flat that are hydrologically significant. Finally, this research will provide new insight into the coupling of landscape and atmospheric phenomena by examining the potential impact of drought versus more commonly cited instigators of change in river sediment dynamics, such as historic alteration of land use /cover and surface hydrology. Research results will be widely disseminated in conference presentations and research journals.