The migration of large-scale bed forms in an estuarine environment: observation and parameterisation for coastal area modelling

上下文。该提案的主题涉及海洋2025：大陆架和海岸过程：13“利物浦湾和邻近河口的形态建模”。它主要适用于WP 3.5“海岸形态动力学和水深演化”，同时也适用于WP 9.1“评估和提高陆架海模型的准确性”。此外，该奖学金将为nerc资助的FORMOST项目（NE/ e015123 / 1,2008 -2010，班戈大学和POL参与）增加重要价值，该项目旨在(i)扩展POL在沉积物运输研究中的现场观测能力，（ii）基于班戈沙运输模型开发新的当地沉积物运输参数化，该模型将在两个沿海地区模型（Telemac和POLCOMS）中实施。Telemac系统已经升级为Bangor模型的参数化版本，这将通过FORMOST作为数据解释的工作工具提供给学生。此外，FORMOST期间将在迪河口外航道，在POL海岸天文台区域内获得新的实地数据，为学生提供背景资料。背景。大型沉积特征（沙波、沙洲和沙洲）的迁移对海底的形态演化起着重要作用。这些特征在沿海沉积物输运模型中没有得到解决，从而导致形态结果的不确定性。该项目将重点关注迪河口大规模床层特征的迁移和迁移，主要从观测的角度研究关键的物理过程，但包括一个建模元素，将允许对实验结果进行有根据的解释。从气候变化背景下的管理角度来看，理解像迪伊河这样的河口作为流动沉积物来源或汇的作用是至关重要的。2007年夏季使用POL的x波段雷达进行的一项试点研究（班戈大学硕士项目，由POL联合监督）表明，在Hilbre岛和Wirral大陆之间的潮间带地区，大规模的沙质特征正在向Dee河口推进。更一般地说，POL的雷达能够监测半径超过4公里的河床形态的移动，它揭示了大型沙质特征也在更深的水域向河口推进。然而，目前尚不清楚的是，各大河床形式对迪河口泥沙收支的相对贡献。研究计划的详细目标是：(i)追踪希尔布雷岛附近潮间带的沙丘，从而详细阐述2007年初步研究的结果。这将突出波浪和洋流对净沙输运的作用。对结果的解释将包括Telemac对现场测量条件的模拟。（ii）利用x波段雷达追踪河口中部较深水域的沙洲和沙丘的运动。可用的/新的ADCP数据和建模将提供解释。Telemac（可能还有POLCOMS）将用于建立负责形态变化的“驱动因素”。（iii）建立一种方法，以Van Rijn（2005）的粗糙度公式为起点，将其引入Telemac，并严格测试其对迪伊河河床形态的影响，从而在沿海地区模型中包含大规模河床特征。最终用户。博士课程将与关注管理问题的最终用户相关。例如，威尔士农村委员会（CCW）和环境局（EA）将出席学生将贡献的FORMOST项目会议。这项研究还将直接为集水区和海岸研究中心做出贡献，该中心是阿伯里斯特威斯大学和班戈大学合作项目的一部分。

CONTEXT. The topic of this proposal relates within Oceans 2025 to: Shelf and coastal processes: 13 'Morphological modelling in Liverpool Bay and adjacent estuaries'. It fits mainly under WP 3.5 'Coastal morphodynamics and bathymetric evolution', while contributing also to WP 9.1 'Assessing and improving the accuracy of shelf sea models'. In addition, this studentship will add significant value to the NERC-funded FORMOST project (NE/E015123/1, 2008-2010, involving Bangor University and POL) which aims to (i) extend POL's field observational capabilities in sediment transport research, and (ii) develop new parameterizations of local sediment transport, based on Bangor's Sand Transport Model, that will here be implemented in two coastal area models (Telemac and POLCOMS). The Telemac system has already been upgraded to include a parameterised version of the Bangor model, and this will be available to the student via FORMOST as a working tool for data interpretation. In addition, new field data will be obtained during FORMOST in the outer channels of the Dee Estuary, within the area of POL's Coastal Observatory, providing background information for the studentship. BACKGROUND. The migration of large-scale sedimentary features (sand waves, banks and bars) contributes significantly to the morphological evolution of the seabed. Such features are not resolved within coastal sediment transport models, giving rise to uncertainty in morphological outcomes. This project will focus on the mobility and migration of large-scale bed features in the Dee Estuary, examining the key physical processes largely from an observational standpoint, but including a modelling element that will allow an informed interpretation of the experimental outcomes. An understanding of the role of estuaries like the Dee in acting as sources or sinks for mobile sediment is essential from a management viewpoint against a background of climate change. The results of a pilot study carried out using POL's X-band radar during summer 2007 (MSc project, Bangor University, jointly-supervised by POL) indicate that large-scale sand features are advancing into the Dee Estuary in the intertidal area between Hilbre Island and the Wirral mainland. More generally, POL's radar, which is capable of monitoring the movement of bed forms over a 4 km radius, has revealed that large sand features are also advancing into the estuary in deeper water. However, what is unknown is the relative contribution of the respective large bed forms to the sediment budget of the Dee Estuary. The DETAILED AIMS of the studentship are to: (i) track sand dunes in the inter-tidal area near Hilbre Island, thus elaborating the results of the 2007 pilot study. This will highlight the role of waves and currents on net sediment transport. Interpretation of the results will include Telemac simulations for the conditions measured on site. (ii) track using X-band radar the movement of sand banks and dunes in deeper water in mid-estuary. Interpretation will be provided both by available/new ADCP data and modelling. Telemac (and possibly POLCOMS) will be used to establish the 'drivers' responsible for morphological change. (iii) establish a methodology for the inclusion of large-scale bed features in coastal area models, taking as a starting point Van Rijn's (2005) roughness formulation, introducing this into Telemac, and critically testing its effect with regard to the bed forms in the Dee. End users. The PhD programme will be of relevance to end users concerned with management issues in the Dee. For example, the Countryside Commission for Wales (CCW) as well as the Environment Agency (EA) will be in attendance at FORMOST project meetings to which the student will contribute. The study will also contribute directly to the Centre for Catchment and Coastal Research, part of the Partnership Project between Aberystwyth and Bangor Universities.