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

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

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.