RAPID: In-Channel Alluvial Benches and Their Environmental Controls

RAPID：河道内冲积台及其环境控制

• 批准号: 0946905
• 负责人: Mary Davis
• 金额: $ 1万
• 依托单位: University of Alabama Tuscaloosa
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-01 至 2011-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0946905&HistoricalAwards=false
• 关键词: RAPID; Channel; Alluvial; Benches; Their

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.

河道内冲积台是河流沉积物的架状沉积物，位于河床上方但主洪泛区表面下方。它们的位置和形态可能会使满岸阶段的常规确定变得复杂，这对于流恢复计划至关重要。它们的存在会影响水力和河岸栖息地的质量，而它们的大量预算是河流动态的重要指标。这项研究的重点是测量基尔帕特里克和巴恩斯于 1964 年在美国东南部皮埃蒙特南部记录的旧河道内长凳的修改，以及可能起源于过去十年皮埃蒙特干旱条件下的较年轻长凳的修改。其他地方的研究人员发现，长凳可能在干旱期间产生，并在潮湿、洪水占主导的情况下被破坏。与过去十年的大部分时间相比，2009 年降雨量恢复较高，因此有可能引发长凳的快速转变，影响整个地区的沉积物收支和河岸栖息地。或者，土地利用历史可能会凌驾于洪水状况之上，成为对台阶形成和破坏的主要控制。该项目旨在利用测量、地形测年技术、洪水数据分析和土地利用变化评估，对台地质量平衡进行区分控制，以阐明山前溪流的台地动态。该项目具有时间敏感性，因为 2009 年迄今的降雨量比皮埃蒙特南部过去十年大部分时间的降雨量要多得多。最近从干旱到湿润条件的气象转变提供了一个无与伦比的机会来记录可能在十年干旱期间形成的河道内长凳，并观察在开始时向较高水流状态转变的影响。这项研究有助于更好地了解河流沉积物储存，因为人们对河道内冲积阶地作为沉积物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着不同的地区进行的研究。因此，这项研究将解决我们目前对先前研究中的长凳的理解是否普遍适用于不同气候环境下的系统。该研究项目研究特定类型河流沉积物储存特征的发生、形成和持续性。因此，它将有助于更好地了解导致河道内沉积物储存的原因、过程和条件，这在帮助了解河流沉积物动态方面具有很大的潜力，有助于使沉积物预算更加精确和有意义。从应用河流地貌学的角度来看，这项研究将为现场确定满岸阶段提供新的见解，通过检查具有水文意义的洪泛区或主河谷平地下方的地貌表面。最后，这项研究将通过研究干旱的潜在影响与更常见的河流沉积物动态变化的诱因（例如土地利用/覆盖和地表水文的历史变化）的潜在影响，为景观和大气现象的耦合提供新的见解。研究成果将在会议报告和研究期刊中广泛传播。