Doctoral Dissertation Research: The Role of Large Woody Debris in a Midwestern Low-Energy Stream: Implications for Stream Naturalization

在研究影响河道地貌结构和动力学的因素时，注意力往往集中在水和沉积物之间的相互作用上。 然而，一些外部因素可以影响这些河流动力学，包括植物材料，福尔斯落入和沿着河床。 虽然越来越多的关注生物群对河流动力学和相关的通道形态的影响，大多数研究都是在快速流动的河流流经非城市地区的地方进行的。 本博士论文研究项目的总体目标是推进大型木质残体（LWD）和低梯度曲流地貌结构和功能之间的相互作用的理解。 该项目将探索LWD储存和运输，有机物保留和各种河流过程之间基于过程的相互作用，包括沉积物运输，三维流动结构和酒吧形式的发展，并将通过制定一套与现存生物河流过程一致的LWD管理指南来为河流自然化工作提供信息。 本计画所要探讨的具体问题包括：（1）曲流河中随钻测井在空间上的分布情形; (2)在这种类型的河流系统中，什么地貌和水文因素会影响木质残体的动态？以及（3）木质残体障碍物如何影响河床物质特性、局部侵蚀和沉积模式、三维水流结构以及单个曲流弯曲尺度上的有机质现存量？ 该项目的设计和方法将通过对曲流弯道的三维流动、曲流河流的底形和平面形态发展以及LWD对河流生态系统的影响的研究来了解。 野外数据将在伊利诺斯州东北部凯恩县福克斯河的一条支流白杨溪的600米蜿蜒段收集。 该研究地点位于一个拉直河段的上游，该河段是去渠化项目的重点，该项目将试图重建一个具有不同流内形态和栖息地的自然功能的曲流系统。 实地研究的组成部分是表征流域内的土地利用变化，GIS促进分析的历史变化，在研究现场的通道位置，并分析现有的历史水文数据。 将特别注意以过程为基础的实地调查，重点是LWD动态和有机物保留整个600米的范围和LWD障碍物和地貌过程之间的相互作用在三个曲流弯曲。 这项研究项目将有助于对曲流地貌动力学的一般了解，特别是这些系统的生物和非生物成分之间的相互作用过程。 这一改进的理解将提供一个更可靠的知识框架，在此基础上，流归化计划的低能量曲流丰富的LWD。 作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立的研究生涯。

When examining the factors that influence the geomorphic structure and dynamics of stream channels, attention tends to focus on interactions between water and sediments. A number of external factors can influence these fluvial dynamics, however, including plant material that falls into and along stream beds. Although increasing attention is being given to the impact of biota on stream dynamics and related channel morphology, most research has been done in locations where fast-moving streams flow through non-urban areas. The overall goal of this doctoral dissertation research project is to advance the understanding of the interactions between large woody debris (LWD) and the geomorphic structure and function of low-gradient meandering streams. The project will explore process-based interactions between LWD storage and transport, organic matter retention, and a variety of fluvial processes, including sediment transport, three-dimensional flow structure, and bar form development, and it will to inform stream naturalization efforts by developing a set of management guidelines about LWD that are consistent with extant biotic-fluvial processes. Specific research questions to be examined in this project include: (1) How is LWD spatially distributed within a meandering stream?, (2) What geomorphic and hydrologic factors affect the dynamics of woody debris in this type of fluvial system?, and (3) How do woody debris obstructions affect bed material characteristics, local patterns of erosion and deposition, three-dimensional flow structure, and organic matter standing stock at the scale of individual meander bends? The project design and methodologies will be informed by research on three-dimensional flow in meander bends, bedform and planform development in meandering streams, and the influences of LWD on stream ecosystems. Field data are will be collected in a 600-meter meandering section of Poplar Creek, a tributary of the Fox River in Kane County in northeastern Illinois. This study site is located directly upstream of a straightened reach that is the focus of a de-channelization project that will attempt to re-establish a naturally functioning meandering system with diverse in-stream morphology and habitats. Among components of the field study are characterization of land-use change within the watershed, GIS-facilitated analysis of historical changes in channel position at the research site, and analysis of available historical hydrologic data. Special attention will be given to process-based field investigations focusing on LWD dynamics and organic matter retention throughout the 600-meter reach and interactions between LWD obstructions and geomorphological processes within three meander bends. This research project will contribute to the general understanding of the geomorphological dynamics of meandering streams, especially process interactions between biotic and abiotic components of these systems. This improved understanding will provide a more reliable framework of knowledge on which to base stream naturalization plans for low-energy meandering streams with abundant LWD. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.