RAPID: Impacts of an Extreme Flood on River Channel Formation and Riparian Forests

该项目将解决极端洪水影响河道形成和稳定以及相关河岸森林结构和组成的复杂方式。以往关于洪水对河流系统影响的研究主要集中在洪水的历史、成因及其水文方面，很少关注洪水对河岸森林结构的影响以及木屑输入对河道稳定性的影响。此外，确实存在的少数研究仅限于山区或干旱地区，其结果在更潮湿的环境中适用性有限。为了评估洪水对河道形态、沉积物和森林结构的长期影响，并帮助预测未来如何管理洪水影响，需要更多的研究来检查不同区域和流域内洪水扰动的变化。这项研究的结果将有助于解决美国林务局对未来洪水趋势增加对联邦设施和国家森林自然资源的影响的担忧。这项研究的结果将在与美国林务局、交通部和周边社区的研讨会上分享。除了有利于自然资源管理外，该项目还将通过密苏里州立大学欧扎克斯环境与水资源研究所（OEWRI）为本科生和研究生提供实地考察和数据分析的教育机会。该项目的目标是描述和分析极端洪水（大于100年的复发间隔）是如何导致河道沿岸森林死亡和木材补充的，并确定哪些变量对这些影响的空间变化负责。该研究计划解决了五个问题：(1)河岸树木的死亡率是否与生物变量（如物种、树木大小、洪水前的木材模式）有系统的关系？(2)死亡率是否与水文地貌变量（如山谷形态、地貌、水流深度）有系统关系？(3)产生了多少木质碎片，哪些树木或场地特征影响了木材运输与堆积的可能性？(4)随着流域面积的增加，不同地点的森林干扰和木材碎片形态是否随尺度而变化？(5)是否可以使用无人机/无人机的航空图像和基于摄影测量的分析来获得关于树木死亡率和木材积累的准确定量数据？本研究将实地调查与图像分析相结合，以评估密苏里州奥扎克地区北福克河有史以来最大的洪水的影响。这些结果将与其他区域研究的结果相结合，以开发一个湿润森林环境中对极端洪水的地貌-生物反应的概念模型。虽然这项研究侧重于评估直接影响，但它将提供对这些影响的空间变异性和恢复方向的见解，这些影响和恢复方向可以在未来十年或更长时间内进行监测，以全面了解恢复过程。这项研究将有助于对河流地貌和生物地理过程的基本理解。

The project will address the complex ways in which extreme floods impact river channel formation and stability and the structure and composition of related riparian forests. Previous studies of flood effects on river systems have focused on the history and causes of the flood, and their hydrology, with little attention to the flood impacts on riparian forest structure and the consequences of woody debris inputs on channel stability. Furthermore, the few studies that do exist have been limited to mountainous or arid regions, and their findings of limited applicability in more humid settings. More studies examining the variation of flood disturbances among different regions and within watersheds are needed to evaluate the long-term influence of floods on channel form, sediment, and forest structure, and to help predict how flood impacts can be managed in the future. The results of this study will help address U.S. Forest Service concerns over future impacts of increased flooding trends on federal facilities and the natural resources of national forests. The findings of this study will be shared during a workshop with the U.S. Forest Service, Department of Transportation, and surrounding communities. Besides benefits for natural resource management, this project will provide educational opportunities for undergraduate and graduate students in fieldwork and data analysis through the Ozarks Environmental and Water Resources Institute (OEWRI) at Missouri State University.The goal of this project is to describe and analyze how an extreme flood (greater than a 100-year return interval) has contributed to riparian forest mortality and wood recruitment along the river channel, and to identify which variables are responsible for the spatial variations in those effects. The research plan addresses five questions: (1) Was riparian tree mortality systematically related to biological variables (e.g., species, size of trees, pre-flood wood patterns)?; (2) Was mortality systematically related to hydro-geomorphic variables (e.g., valley morphology, landform, flow depth)?; (3) How much woody debris was generated and what tree or site characteristics affected the likelihood of wood transportation versus accumulation?; (4) Do forest disturbance and wood debris patterns vary with scale at different sites along a gradient of increasing drainage area?; and (5) Can aerial imagery from drones/UAVs and photogrammetry-based analysis be used to acquire accurate quantitative data regarding tree mortality and wood accumulation? This study combines field research with imagery analysis to evaluate the effects of the largest flood on record on the North Fork River in the Missouri Ozarks. The results will be combined with those from other regional studies to develop a conceptual model of geomorphic-biotic response to extreme floods in a humid forest environment. While this study focuses on the assessment of immediate effects, it will offer insights into the spatial variability of those effects and the direction of recovery which can be monitored over the next decade or longer to gain a full understanding of the recovery process. The research will inform fundamental understanding of fluvial geomorphic and biogeographic processes.