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

本博士论文研究项目将调查森林砍伐对河流泥沙蓄积的影响。森林砍伐活动减少了河流系统中大量木质碎屑的存在，从而增加了水的流动性，减少了重要的生物避难所和泛滥平原的形成。该项目将为以过程为基础理解河流动态和人类相关地貌变化对河流侵蚀率的影响提供新的见解。通过更好地了解改变的地貌模式对景观的影响，这项研究有可能将基岩(层)阶地确定为当前地质时代的地理分界线，许多科学家将其称为人类世。项目成果将为寻求建立更好的河流系统管理和恢复战略的水运工程师和泛滥平原恢复机构提供信息。博士生将与当地学校和学生组织合作，开发旨在促进这些机构的STEM教育计划的教育材料。作为博士论文研究改进奖，该奖项将为有前途的学生建立强大的独立职业生涯提供支持。清除河流系统中的大片木质碎屑会减少其泥沙负荷，并可能导致河流快速切割，从而减缓泛滥平原的形成，改变生态系统供水，并影响洪水淹没模式。这项研究项目将通过研究太平洋西北部河流基岩阶地的形成，探讨与人类有关的木质碎片清除的空间和时间影响。这位博士生将使用木炭的放射性碳测年和泛滥平原沉积物的一种新的铅-210测年方法来确定河流切割的开始和速度。将与以前研究中得出的长期切割率进行比较分析，以评估当前河流对与人类相关的活动的反应。学生将把档案研究与数字模型结合起来，以评估森林砍伐对河谷的长期地形影响。这些方法在不同时空尺度上的结合将决定人类世的地形特征是否由于大规模的林业实践而出现。

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.