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2017 Archive
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Author(s): Natasha Dacic
Presentation: oral
Post-fire debris flows play an important role in shaping terrestrial and aquatic ecosystems by delivering sediment, wood, and nutrients from hillslopes to river channels and altering geomorphic complexity. Greater complexity (e.g., wood jams and multithread channels) has been correlated with enhanced biodiversity. Here, we examine two hypotheses: 1) geomorphic complexity correlates with time since fire such that the greatest complexity corresponds to intermediate recovery, and 2) in-channel carbon storage is positively correlated with time since fire and geomorphic complexity. We examined three sub-basins (Rapid River, Pistol Creek, and Mayfield Creek) with different wildfire histories within the Middle Fork of the Salmon River, ID to determine how complexity responds to wildfire over time. At each site we selected a 600-800 m continuous reach with consistent channel type and evidence of post-fire debris flow input. Complexity metrics were computed and analyzed for significant differences by using a one-way ANOVA test and Tukey’s multiple comparison penalty. Five of the complexity metrics measured were significantly different among the three sites (p < 0.10). Pistol Creek, with an intermediate time since fire, shows the highest variability and range in geomorphic complexity. Next steps include analyzing the carbon content of sediment and quantifying wood loads.
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