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The predominance of post‐wildfire erosion in the long‐term denudation of the Valles Caldera, New Mexico
Author(s) -
Orem Caitlin A.,
Pelletier Jon D.
Publication year - 2016
Publication title -
journal of geophysical research: earth surface
Language(s) - English
Resource type - Journals
eISSN - 2169-9011
pISSN - 2169-9003
DOI - 10.1002/2015jf003663
Subject(s) - denudation , erosion , lithology , caldera , geology , hydrology (agriculture) , sediment , physical geography , watershed , geomorphology , environmental science , volcano , geography , geochemistry , paleontology , geotechnical engineering , tectonics , machine learning , computer science
Wildfires can dramatically increase erosion rates over time scales on the order of several years, yet few data firmly constrain the relative importance of post‐wildfire erosion in the long‐term denudation of landscapes. We tested the hypothesis that wildfire‐affected erosion is responsible for a large majority of long‐term denudation in the uplands of the Valles Caldera, New Mexico, by quantifying erosion rates in wildfire‐affected and non‐wildfire‐affected watersheds over short (~10 0 –10 1 years) time scales using suspended sediment loads, multitemporal terrestrial laser scanning, and airborne laser scanning and over long (~10 3 –10 6 years) time scales using 10 Be inventories and incision into a dated paleosurface. We found that following the Las Conchas fire in 2011, mean watershed‐averaged erosion rates were more than 1000 µm yr −1 , i.e., ~10 3 –10 5 times higher than nearby unburned watersheds of similar area, relief, and lithology. Long‐term denudation rates are on the order of 10–100 µm yr −1 . Combining data for wildfire‐affected and non‐wildfire‐affected erosion rates into a long‐term denudation rate budget, we found that wildfire‐affected erosion is responsible for at least 90% of denudation over geologic time scales in our study area despite the fact that such conditions occur only at a small fraction of the time. Monte Carlo analyses demonstrate that this conclusion is robust with respect to uncertainties in the rates and time scales used in the calculations.