Collaborative Research: The interaction of waves, tidal currents and river outflows and their effects on the delivery and resuspension of sediments in the near field

合作研究：波浪、潮流和河流流出的相互作用及其对近场沉积物输送和再悬浮的影响

• 批准号: 1334325
• 负责人: James Kirby
• 金额: $ 48.34万
• 依托单位: University of Delaware
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1334325&HistoricalAwards=false
• 关键词: Collaborative; Research; interaction; waves; tidal

This study will focus on the mechanisms for sediment resuspension and removal in the near field of a river mouth plume characterized by a combination of strong freshwater discharge, significant vertical shear resulting from stratification, and strong surface wave conditions. It is hypothesized that the dispersal pathway of river-borne sediment is possibly more often governed by resuspension events in the region of sediment trapping, as opposed to only being an a priori property of the riverine discharge. Further, surface waves are hypothesized to be an important component of the overall physical mechanism of bottom stress and sediment resuspension in river mouths and coastal inlets, leading to greatly enhanced potential for sediment transport. In order to address these hypotheses, the researchers will further develop and utilize a nonhydrostatic model (NHWAVE) with capabilities to handle salinity stratification and suspended sediment in both wave-resolving and wave-averaged forms, using, in particular, results from ongoing NSF-funded work on river plume dynamics. The model will be validated against a high-resolution data set for instabilities in sheared buoyant plume flow in order to establish the accuracy of the formulation at high resolution, and against a larger scale transect of data from the Mouth of the Columbia River (MCR) to verify basic wave and circulation processes in the model. The model will be applied to the MCR in order to study the interplay of tidally pulsed river plume and waves and the resulting removal and resuspension of sediments in the vicinity of ebb-tidal plume liftoff, and will be further used in interpreting results from the ONR-sponsored RIVET-II experiment, conducted in June 2013.Estuaries and river mouths provide the pathway for riverine supply of sediments to the coast and the distribution of sediments to the shelf and deep ocean. This project will study the influence and coupling of tidal currents, river discharges and surface waves in determining the sediment transport regime in coastal inlets. The first task will be to develop and test both wave-resolving and wave averaged versions of a flexible, parallelized nonhydrostatic model NHWAVE, which has recently been extended to incorporate density stratification and the presence of a suspended sediment load, thus providing the basic tools needed for high resolution process studies. The further development of the model is important for several reasons. First, the strong vertical components of motion associated with the tidal genesis of fronts in surface advected plumes, and the occurrence of strong resuspension events near regions of plume liftoff, require the application of fully nonhydrostatic models. In addition, wave processes in strongly sheared flows associated with surface-advected plumes are not adequately described by either existing wave resolving models or by theory for wave-averaged flows in weakly sheared environments as presently used in standard coastal ocean models, thus requiring improved model formulations.This research will advance the understanding of sedimentation processes at the intersection of river and coastal environments. The model development effort will further the recent trend towards use of nonhydrostatic formulations in coastal ocean models by incorporating wave-resolving capabilities, leading to the ability to represent a full range of wave, current, stratification, turbulence and sediment processes in a common computational framework utilized at realistic scales. The resulting model will greatly enhance the community's ability to assess the effect of complex, irregular wave processes on bottom stress and sediment resuspension, leading to a better understanding of the pathways for sediment motion from river to shelf. The resources from the grant will partially support three doctoral graduate researchers, and undergraduate summer fellows through an existing REU program. The PIs will continue their efforts to promote science and research to a K-12 population through continued and expanded participation in University of Delaware programs such as Coast Day, Engineering Cool Stuff Camp and Young Engineers Camp.

本研究将侧重于沉积物再悬浮和去除的机制，在近场的河口羽流的特点是强大的淡水排放，显着的垂直剪切分层，和强大的表面波条件的组合。据推测，河流携带的沉积物的扩散途径可能更经常地由再悬浮事件在该地区的沉积物截留，而不是仅仅是一个先验属性的河流流量。此外，表面波被假设为底部应力和沉积物再悬浮在河口和沿海入口的整体物理机制的一个重要组成部分，从而大大提高了潜在的泥沙输运。为了解决这些假设，研究人员将进一步开发和利用一个非流体静力学模型（NHWAVE），该模型能够以波浪解析和波浪平均的形式处理盐度分层和悬浮沉积物，特别是利用NSF资助的河流羽流动力学研究的结果。该模型将针对剪切浮力羽流不稳定性的高分辨率数据集进行验证，以确定高分辨率下公式的准确性，并针对来自哥伦比亚河口（MCR）的更大规模数据断面进行验证，以验证模型中的基本波和环流过程。该模型将应用于MCR，以研究潮汐脉冲河流羽流和波浪的相互作用，以及由此产生的落潮羽流抬升附近沉积物的去除和再悬浮，并将进一步用于解释ONR赞助的RIVET-II实验的结果，河口和河口是河流向海岸提供沉积物的通道，也是沉积物向陆架和深海分布的通道。本项目将研究潮汐流、河流流量和表面波在确定沿海入口沉积物输运状况方面的影响和耦合。第一项任务将是开发和测试一个灵活的、并行的非流体静力学模型NHWAVE的波浪解析和波浪平均版本，该模型最近已扩展到包括密度分层和悬浮泥沙负荷的存在，从而提供高分辨率过程研究所需的基本工具。该模型的进一步发展是重要的，原因有几个。首先，强烈的垂直分量的运动与潮汐成因的前表面平流羽流，并发生强烈的再悬浮事件附近地区的羽流升空，需要应用完全非流体静力学模型。此外，在强烈剪切流与表面平流羽流的波过程中没有充分描述现有的波解析模型或理论的弱剪切环境中的波平均流，目前在标准的沿海海洋模型，因此需要改进的模型formulations.This研究将推进在河流和沿海环境的交汇处的沉积过程的理解。模型开发工作将进一步推动最近在沿海海洋模型中使用非流体静力学公式的趋势，方法是结合波浪分辨能力，从而能够在现实尺度下使用的共同计算框架中代表各种波浪、海流、分层、湍流和沉积过程。由此产生的模型将大大提高社区的能力，以评估复杂的，不规则的波浪过程对底部应力和沉积物再悬浮的影响，从而更好地了解沉积物从河流到大陆架的运动路径。来自赠款的资源将部分支持三名博士研究生研究人员，并通过现有的REU计划本科暑期研究员。PI将继续努力，通过继续和扩大参与特拉华州大学的海岸日、工程酷物营和青年工程师营等项目，向K-12人口推广科学和研究。