1. How Debris Flow Channels Refill in the Western Cascades Arianna Lambie Advisor: Frederick Swanson Ecosystem Informatics Summer Institute August 2007

2. Why we care Debris flows change landscapes and influence ecosystems

3. What influences flow impacts? Frequency Volume

4. My objectives 1) Quantify material volume Wood Sediment 2) Determine accumulation rates 3) Identify factors influencing accumulation

5. Methods

6. Study Site: HJ Andrews Forest

7. Data Collected Wood –diameter, length, orientation Sediment –width, length, depth, composition, obstruction Channel in general –Slope, width, other observations

8. Surveying the Channels

11. Results

12. Wood and sediment volumes correlate and increase over time

13. Approximating Accumulation Rates

15. Large wood is a primary sediment storage mechanism

16. The Sediment Story Sediment Wood Hillslump Remnant debris flow deposits Material in channel Root throw, Soil creep, and subsequent transport Slump earthflow Previous debris flow Fluvial transport Bedrock channel slope Forest management, Road building Size, age, health of trees Debris flow impacts Debris flow frequency Solid line = transport Dashed = influence

17. Extending the Study Fill and rework the influence diagram –Compile data from previous studies –Continue channel data collection, plantations Apply math –Fit equations to accumulation rates –Quantify influence pathways Investigate biologic impacts –In channel –Downstream

18. Summary Frequency Volume Important Debris Flow Characteristics HJ Andrews Forest Sediment and wood accumulate faster than in Coast Range Wood blocks 87% of sediment Implications for forest management that changes wood input Piecing together the sediment budget story