Doctoral Dissertation Research: Investigating the Influence of Deforestation on River Incision and Landscape Change

University Of Washington, Seattle WA

Investigators

Abstract

This doctoral dissertation research project will investigate the impact of deforestation on sediment storage in streams. Deforestation activities reduce the presence of large woody debris in river systems, which results in increased mobility of water and decreased formation of vital biological refuges and floodplains. This project will provide new insights into the process-based understanding of river dynamics and the impacts of human-related geomorphic changes on river erosion rates. By providing a better understanding of the landscape impacts of modified geomorphological patterns, this research has the potential for identifying bedrock (strath) terraces as a physiographic demarcator of the current geologic epoch, which has been called the Anthropocene by many scientists. Project findings will inform water transportation engineers and floodplain restoration agencies seeking to institute better management and restoration strategies for river systems. The doctoral student will work with local schools and student organizations to develop educational materials directed at furthering STEM education programs at those institutions. As a Doctoral Dissertation Research Improvement award, this award will provide support to enable a promising student to establish a strong independent career. Removal of large woody debris from river systems reduces their sediment load and can lead to rapid river incision, thus slowing floodplain formation, changing ecosystem water supply, and affecting flood inundation patterns. This research project will address the spatial and temporal impact of human-related woody debris removal by examining the formation of bedrock terraces in the rivers of the Pacific Northwest. The doctoral student will use radiocarbon dating of charcoal and a novel method of lead-210 dating of floodplain sediment to determine the onset and rate of river incision. A comparative analysis will be performed with long-term incision rates derived during previous studies to assess the current river response to human-related activities. The student will couple archival research with a numerical model in order to assess the long-term topographic impact of deforestation on river valleys. The integration of these methodologies across various spatio-temporal scales will determine if a topographic signature of the Anthropocene is emerging as a result of large-scale forestry practices.