Geomorphic response of six headwater basins fifteen years after the La Mesa Fire
White WD and Allen CD. 1996. Geomorphic response of six headwater basins fifteen years after the La Mesa Fire. Pages 95-113. In White WD and Allen CD (ed): Fire effects in Southwestern forests: proceedings of the Second La Mesa Fire Symposium, Los Alamos, New Mexico, March 29-31, 1994. Los Alamos, New Mexico. March 29-31, 1994. US Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. Fort Collins, Colorado. General technical report RM-GTR-286
"A study was set up in 6 small headwater basins in the Rito de los Frijoles watershed 3 months after the La Mesa fire (1977) to investigate the factors important to hillslope erosion as a response to the disequilibrium conditions created by fire. Data is presented from the 1992 re-measurements, which indicate that these factors include the degree of ash development, the amount of upslope catchment area, the degree of slope, and the type or complexity of slope. The efficiency of transport of fire-derived sediment was related to the density and continuity of drainage lines. Early controls to fire related erosion proved to be needle cast from unburned crowns, and climatic variability (e.g., the precipitation differences between altitudes). Fifteen years following the La Mesa fire, hillslope erosion had been interrupted by downed, burned trees and increased ground surface microtopography afforded by the aggradational building of grass pedestal and cryptogamic crusts. The increased ground surface roughness encouraged infiltration from intensely burned areas. Infiltration often became shallow ground-water interflow which surfaced at the top margins of tributary canyons. The gathering of sediment-free runoff in the tributary and trunk canyons entrains the temporarily stored sediment derived from the mesa tops immediately following the fire. Present day sediment delivery from burned areas of the mesa tops was derived primarily from moderately burned basins. While the characteristic needle cast protects the moderately burned basins' ground surface from rain drop impact and channelized overland flow (rilling), needle cast discouraged the growth of cryptogamic crusts. Without the combined infiltration-encouraging factors of cryptogamic crusts and downed trees (which are fewer in moderately burned basins), precipitation in moderately burned areas generally concentrated in the drainages and channel incision resulted. Storage of this sediment occurred where drainages widen, such as the mouth of the moderate burn basin on Burnt Mesa, and on the lower gradient, mesa top trunk channels." [Tree CD]
- Type
- Conference Proceeding Paper
- Authors
- White, William; Allen, Craig
- Units
- BAND
- Keywords
- Erosion, Fire Effects, Geomorphology, Physical Sciences, Rito de los Frijoles Bandelier National Monument