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Factors affecting connectivity and sediment yields following wildfire and post-fire salvage logging in California's Sierra Nevada.
Olsen WH, Wagenbrenner JW, Robichaud PR. 2021.
Factors affecting connectivity and sediment yields following wildfire and post-fire salvage logging in California's Sierra Nevada..
Hydrological Processes 35: DOI: 10.1002/hyp.13984.
Keywords: hillslope erosion, hydrologic connectivity, post-fire erosion, rill erosion, salvage logging, sediment yield, wildfire
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Abstract:
Sediment delivery following post-fire logging is a concern relative to water quality.
While studies have assessed the effect of post-fire logging on sediment yields at different
spatial scales, none have explicitly identified sediment sources. Our goal was
to quantify post-fire and post-salvage logging sediment yields and use rill patterns to
identify sediment sources. We measured the extent and type of logging disturbance,
length of rills per unit area or “rill density”, ground cover, and sediment yields in nine
logged and five control small catchments or “swales”, 0.09 to 0.81 ha, for 5 years
after the 2013 Rim Fire in California's Sierra Nevada. The logged swales had a mean
ground disturbance of 31%. After the first wet season following logging, there
was no difference in either mean rill density (0.071 and 0.088 m m-2, respectively)
or mean transformed, normalized sediment yields between the control and logged
swales. Untransformed mean sediment yields across three sites ranged from
0.11–11.8 and 1.1–3.2 Mg ha-1 for the controls and salvage-logged swales, respectively.
Rill density was strongly related to sediment yield and increased significantly
with the amount of high-traffic skid trail disturbance in logged swales. Rill density
was not significantly related to the amount of bare soil despite a significant relationship
between sediment yields and bare soil. Rills usually initiated in bare soil and frequently
connected high traffic skid trails to the drainage network after being diverted
by waterbars. Rill connectivity and sediment yields decreased in control and logged
swales where vegetation or other surface cover was high, suggesting this cover disconnected
rills from the drainage network. Increasing ground cover on skid trails and
between areas disturbed by post-fire logging and stream channels may reduce sediment
yields as well as the hydrologic connectivity between hillslopes and the drainage
network.
Moscow FSL publication no. 2021e
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