HR: 0830h
AN: H51D-1105    [PDF]
TI: Factors Associated With Post-fire Sediment Yields From Hillslope Plots in the Colorado Front Range
AU: * Benavides-Solorio, J
EM: jdedios@cirpac.inifap.conacyt.mx
AF: INIFAP-Centro de Investigacion Regional del Pacifico Centro, Parque Los Colomos s/n Col. Providencia, Guadalajara, Jal 44600 Mexico
AU: MacDonald, L H
EM: leemac@cnr.colostate.edu
AF: Colorado State University, Department of Forest, Rangeland and Watershed Stewardship, Fort Collins, CO 80523 United States
AB: In recent years there has been a large increase in the number and size of wildfires in the mid-elevation zones of the Colorado Front Range. High-intensity rainstorms after these fires have increased erosion rates by several orders of magnitude and severely affected downstream aquatic resources. The objective of this study was to measure sediment production rates at the hillslope scale and determine the key controlling variables. To this end 48 sediment fences have been continuously monitored in three wildfires and three prescribed fires at elevations ranging from 1670 to 3050 m. The most intensively-studied area is the Bobcat fire, which burned 43 km$^{2}$ in June 2000. Within this fire sediment production rates exceeded 10 Mg ha$^{-1}$ yr$^{-1}$ for areas burned at high severity. Prescribed fires produced substantially less sediment than the corresponding wildfires. Sediment production rates from sites burned at high severity were nearly 200 times higher than sites burned at moderate severity. Nearly all of the erosion occurred as a result of summer rainstorms rather than winter snowmelt. Sediment production rates per unit area were 2-3 times higher in swales or small drainages than from planar hillslopes. Data from the older fires indicate that sediment production rates remain elevated for sites burned at high severity for at least three years after burning. When the data from all fires were combined, 77% of the variability in sediment production rates could be explained by fire severity, percent bare soil, rainfall erosivity, soil water repellency, and soil texture. A simpler model using only percent cover and rainfall erosivity had a R$^{2}$ of 0.62. Various models were tested against an independent data set from the Bobcat fire, and this showed that fire severity, percent bare soil, and rainfall erosivity could successfully predict post-fire erosion rates. The understanding and models developed in this project can help land managers predict the likely impacts from future wildfires and assist in the design of more effective post-fire rehabilitation techniques.
DE: 1803 Anthropogenic effects
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
SC: Hydrology [H]
MN: 2003 Fall Meeting