Morphological Evolution of an Energetic Tidal Channel: Quantifying Frictional Feedbacks Across Multiple Scales Using High Resolution Observations and Modeling

该项目将联合收割机结合先进的观测技术和高分辨率的水动力模拟，以量化潮汐通道中底形的形态演变及其与水动力粗糙度的反馈。在复杂的沿海环境中，我们理解多尺度相互作用的能力往往受到观测数据或建模框架中的差距的限制。这项研究将跨越这些差距，以解决形态进化和摩擦效应的基本问题。形态动力学模型在模拟几个世纪到几千年的盆地尺度演变方面取得了很大进展，但定量技术和基于过程的评估仍然受到观测的限制。同样，水动力学模型已纳入各种过程，可以有助于有效的粗糙度和改变预测的速度和床应力，但定量评估摩擦的规模模型参数化的优点，包括复杂的粗糙度配方模糊。这项研究将直接解决空间和时间分辨率的这些限制，其结果将更广泛地适用于更大规模和更缓慢演变的沿海环境。这将大大提高我们描述和管理各种沿海过程的能力。淹没，富营养化，有害藻华，以及长期的形态响应海平面上升的后障和浅河口环境都取决于小尺度水动力和底形耦合研究。该项目将支持研究生和博士后的培训。多学科的主题和研究方法，结合先进的观测和建模工具将准备他们作出贡献，无论是在基础研究或沿海系统的工程和管理。在近岸海洋，底形在空间和时间尺度的级联相互作用。波痕响应于潮汐速度，涟漪迁移的收敛和发散导致巨波痕的生长和运动。类似地，在小潮到事件时间尺度上的巨型涟漪演化有助于沙丘和更大尺度特征的形成。利用自主地面和空中飞行器，该团队将绘制出动态潮汐通道在这一强迫条件范围内的演变，明确解决从10厘米到100米波长的光谱演变。船上和系泊观测还将测量床形对多尺度上覆流的摩擦效应，从而提供局部湍流应力和正压压力梯度之间的直接比较。一个空间有限的和动态演变的域允许高分辨率的水动力学和沉积物输运系统中的建模，包括前所未有的定量评价的形态响应。小尺度、基于过程的建模将与大尺度形态动力学模拟配对，以将底形尺度的水动力特征与有效粗糙度的综合效应联系起来。亚网格尺度粗糙度的参数化将与观测结果进行比较，以评估多个尺度的底形如何影响变化的潮汐力的摩擦响应。

This project will combine advanced observational techniques with high resolution hydrodynamic modeling to quantify the morphological evolution of bedforms in a tidal channel and their feedbacks with hydrodynamic roughness. In complex coastal environments, our ability to understand interactions across multiple scales is often limited by gaps in the observational data or modeling framework. This study will span those gaps in order to address fundamental questions on morphological evolution and frictional effects. Morphodynamic modeling has made great progress at simulating basin-scale evolution over centuries to millennia, and yet quantitative skill and process-based assessments remain limited by observations. Similarly, hydrodynamic models have incorporated various processes that can contribute to effective roughness and alter predicted velocities and bed stress, and yet quantitative assessment of friction at the scale of the model parametrizations makes the merits of the inclusion of complex roughness formulations ambiguous. This research will directly address these limitations in spatial and temporal resolution, and the results will be applicable more broadly to larger scale and more slowly evolving coastal settings. This would significantly improve our abilities to characterize and manage a wide range of coastal processes. Inundation, eutrophication, harmful algal blooms, and long-term morphological response to sea level rise in back-barrier and shallow estuarine environments all depend on the small-scale hydrodynamic and bedform coupling studied here. This project will support the training of both a graduate student and postdoc. The multidisciplinary topic and a research approach that integrates advanced observational and modeling tools will prepare them to make contributions either in basic research or engineering and management of coastal systems.In the nearshore ocean, bedforms interact across a cascade of spatial and temporal scales. Ripples respond to tidal velocities, and convergences and divergences in ripple migration lead to the growth and movement of mega-ripples. Similarly, mega-ripple evolution at spring-neap to event time scales contributes to the formation of dunes and larger scale features. Using autonomous surface and aerial vehicles the team will map out the evolution of a dynamic tidal channel across this range of forcing conditions, explicitly resolving the spectral evolution from wavelengths of 10s of cm to 100s of m. Shipboard and moored observations will also measure the frictional effects of the bedforms on the overlying flow across multiple scales, providing a direct comparison between local turbulent stresses and the barotropic pressure gradient. A spatially limited and dynamically evolving domain permits high resolution modeling of the hydrodynamics and sediment transport in the system, including unprecedented quantitative evaluation of the morphological response. Small scale, process-based modeling will be paired with larger scale morphodynamic simulations to link hydrodynamic features at the bedform scale with the integrated effect on effective roughness. Parameterization of subgrid-scale roughness will be compared with observations to assess how multiple scales of bedforms affect the frictional response with changing tidal forcing.