Wood budgets and wood mobility in two headwater streams in the Pacific Northwest, USA

Keywords: fluvial geomorphology, large wood, headwater streams
Session Type: Virtual Paper Abstract
Day: Friday
Session Start / End Time: 2/25/2022 11:20 AM (Eastern Time (US & Canada)) - 2/25/2022 12:40 PM (Eastern Time (US & Canada))
Room: Virtual 19

Abstract

Large wood in river systems influences sediment transport, hydraulics, channel form, and geomorphic complexity, and creates habitat for fish and other biota. However, measurements of wood in river systems typically span short periods of time, limiting our ability to understand long-term wood dynamics. We present a tagged-wood study conducted over 20 years from Caspar Creek Experimental Watershed, USA. In-stream wood was surveyed approximately every 2 years in the South Fork Caspar Creek watershed, which was heavily logged without the use of protective buffer strips near the stream in the 1970s, and the North Fork Caspar Creek watershed, which was logged in the late 1980s and early 1990s with protective buffer strips. We present data on the distance that individual wood pieces moved between each survey, relating the displacement length to stream discharge metrics, wood piece characteristics, and stream geomorphology. We find that piece dimensions (diameter and the piece length relative to the channel width), the position of wood in the channel, and high flow events promote wood entrainment and increase displacement lengths. In addition, the South Fork, which was more heavily impacted by logging, still contains less wood volume compared to the North Fork, pointing to the long-term impacts of management decisions on in-stream wood loads. Because of the long-term, high temporal resolution of our dataset, our results provide insight into wood dynamics over time and can inform efforts to increase and retain wood in river systems.