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

洪水泛滥通常使河流与河漫滩之间的物质和能量交换最大和最突然，受影响地区的大小高度依赖于河道和河漫滩地貌。鉴于沿海平原的脆弱性，越来越多的强度和频率的热带气旋的风雨影响，这是至关重要的，以提高我们的理解这些影响河流洪泛区在这些环境中的相互作用。这方面的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。德克萨斯州沿海弯曲的使命河也是使命-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的路径上，该飓风于2017年8月25日首次登陆。飓风引发的暴雨仅导致河流出现中度洪水，但强风导致大量树木被吹倒，河流及其洪泛区出现大量木质残体。LWD造成堵塞和障碍，可以改变河流的流量，并将洪水和河流重新引导到洪泛区环境中，导致河流系统的侵蚀和重新配置。这项快速反应研究项目将是对飓风哈维吹落树木影响的第一次评估。也是最早的飓风之一沿海河流系统。预计这些成果将通过增进关于热带气旋对河流系统的极端风力影响的知识库，为关于这一主题的河流地貌学方面非常有限的文献作出贡献。研究结果将为在MANERR开发成功的河流栖息地景观和生态系统管理提供见解，适用于可能包括人类居住和基础设施的类似系统。这项研究将与德克萨斯州海洋补助金内的MANERR和沿海恢复力合作（CRC）的工作人员/研究人员建立伙伴关系。调查结果将通过MANERR环境管理计划和CRC教育和外展社区传播，旨在提高沿海社区，资源管理人员和土地使用规划者对热带气旋对河流和洪泛区系统以及相关生态系统服务的影响的认识。拟议的研究将为来自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：飓风哈维的树木吹倒和LWD对使命河道和洪泛区之间的水文表面连通性有何影响？该研究由两个目标驱动：1）定量确定河漫滩上树木吹倒和LWD输入河道的空间范围和模式; 2）评估极端事件（即，飓风风力）对洪水泛滥和河道与洪泛平原之间的水文表面连通性的空间和时间背景。为了实现这些目标，该研究将整合实地调查，高空间和光谱分辨率的地理空间数据，以及流体动力学建模。这项研究的结果将推进我们的过程中的理解，如何突然变化的河漫滩配置，由于飓风风力影响地表水引起的相互作用，河流-河漫滩系统，以及这种影响如何在不同的河流阶段的条件。

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.