RAPID: Tree Blowdown Impacts of Hurricane Harvey on Hydrologic Surface Connectivity in a Coastal River and Its Floodplain

洪水泛滥通常会导致河流与其洪泛区之间发生最大、最突然的物质和能量交换，受影响区域的大小高度依赖于河道和洪泛区地貌。鉴于沿海平原容易受到强度和频率不断增加的热带气旋风雨影响的影响，提高我们对这些环境中河流-洪泛区相互作用的影响的理解至关重要。这些知识对于成功保护和管理沿海平原河流系统、其生态系统和生态系统服务也至关重要。位于德克萨斯州海岸湾的米申河 (Mission River) 也是米申-阿兰萨斯国家河口研究保护区 (MANERR) 的一部分，位于飓风哈维的破坏性核心路径上，哈维于 2017 年 8 月 25 日首次登陆。飓风带来的强降雨仅导致河流出现中度洪水；然而，极端大风导致河流及其漫滩上大量树木倒塌和大量木质碎片（LWD）。 LWD 会造成堵塞和障碍，从而改变河流的流量，并将洪水和河水重新引导到洪泛区环境中，从而导致河流系统的侵蚀和重新配置。这个快速反应研究项目将是对飓风哈维的树木倒塌影响的首次评估？是第一个飓风吗？在沿海河流系统上。通过推进关于热带气旋对河流系统的极端风影响的知识库，预计研究结果将为关于该主题的河流地貌学非常有限的文献做出贡献。研究结果将为MANERR河流栖息地开发成功的景观和生态系统管理提供见解，并适用于可能包括人类居住和基础设施的类似系统。这项研究将与 MANERR 和德克萨斯州海洋补助金内的海岸恢复合作组织 (CRC) 的工作人员/研究人员建立合作伙伴关系。研究结果将通过 MANERR 环境管理计划以及 CRC 教育和外展社区传播，旨在提高沿海社区、资源管理者和土地利用规划者对热带气旋对河流和洪泛区系统及相关生态系统服务影响的认识。拟议的研究将为代表性不足群体的研究生和本科生提供培训和指导。本研究旨在回答以下问题：飓风哈维的树木倒塌和 LWD 对 Mission 河道和洪泛区之间的水文表面连通性有何影响？该研究有两个目标：1）定量确定洪泛区树木被倒塌的空间范围和模式以及随钻测井输入河道的情况； 2) 评估极端事件（即飓风级大风）后树木倒塌和随钻测井对洪水泛滥以及河道和洪泛区之间时空背景下水文表面连通性的影响。为了实现这些目标，该研究将整合现场调查、高空间和光谱分辨率地理空间数据以及流体动力学建模。这项研究的结果将促进我们对飓风造成的洪泛区结构的突然变化如何影响河流-洪泛区系统内地表水引起的相互作用以及这种影响如何在一系列河流水位条件下变化的过程的理解。

Flood inundation typically enables the largest and most abrupt material and energy exchanges between a river and its floodplain and the size of the area affected is highly dependent on river-channel and floodplain geomorphology. Given the vulnerability of coastal plains to the wind and rain impacts of tropical cyclones with increasing strength and frequency, it is critical to advance our understanding of these impacts on river-floodplain interactions in these environments. This knowledge is also crucial to successful preservation and management of the coastal plain river systems, their ecosystems, and ecosystem services. The Mission River on the Coastal Bend of Texas, which is also a part of the Mission-Aransas National Estuarine Research Reserve (MANERR), was on the path of the destructive core of Hurricane Harvey, which made its first landfall on Aug. 25, 2017. Hurricane driven heavy rainfall resulted only in moderate flooding of the river; however, the extreme winds induced a substantial amount of tree blowdowns and large woody debris (LWD) on the river and its floodplain. LWD creates logjams and barriers that can alter the flow of the river and redirect flood and river flow into floodplain environments, resulting in erosion and reconfiguration of the river system. This rapid-response research project will be the first assessment of the tree blowdown impacts of Hurricane Harvey ? and one of the first of any hurricane? on a coastal river system. The outcomes are expected to contribute to the very limited literature in fluvial geomorphology on the subject by advancing the knowledge-base on extreme wind impacts of tropical cyclones on river systems. The findings will provide insights for developing successful landscape and ecosystem management of the riverine habitats at the MANERR, with applicability to similar systems which might include human habitation and infrastructure. This research will establish partnerships with staff/researchers at the MANERR and Coastal Resilience Collaborative (CRC) within Texas Sea Grant. The findings will be disseminated via the MANERR environmental stewardship program and CRC education and outreach communities with the aim of increasing awareness of coastal communities, resource managers, and land-use planners on the impacts of tropical cyclones on river and floodplain systems and associated ecosystem services. The proposed study will provide training and mentoring of graduate and undergraduate students from underrepresented groups.This study aims to answer the question: What are the tree blowdown and LWD impacts of Hurricane Harvey on hydrologic surface connectivity between the Mission River channel and floodplain? The study is driven by two objectives: 1) determine quantitatively the spatial extent and patterns of tree blowdowns on the floodplain and LWD inputs into the river channel; 2) evaluate the impact of tree blowdowns and LWD after an extreme event (i.e., hurricane-force wind) on flood inundation and hydrologic surface connectivity between the river channel and the floodplain in a spatial and temporal context. To address these objectives, the study will integrate field investigations, high spatial- and spectral-resolution geospatial data, and hydrodynamic modeling. Findings of the study will advance our process understanding of how an abrupt change in floodplain configuration due to hurricane-force wind influence the surface water induced interactions within river-floodplain systems and how this influence varies across a range of river-stage conditions.