Open AccessCharacterizing arid region alluvial fan surface roughness with airborne laser swath mapping digital topographic data
Author(s) -
Frankel Kurt L.,
Dolan James F.
Publication year - 2007
Publication title -
journal of geophysical research: earth surface
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2006jf000644
Subject(s) - geology , alluvial fan , landform , geomorphology , arid , alluvium , deposition (geology) , surface roughness , tributary , digital elevation model , alluvial plain , hydrology (agriculture) , remote sensing , sediment , paleontology , cartography , geography , physics , geotechnical engineering , structural basin , quantum mechanics
Range‐front alluvial fan deposition in arid environments is episodic and results in multiple fan surfaces and ages. These distinct landforms are often defined by descriptions of their surface morphology, desert varnish accumulation, clast rubification, desert pavement formation, soil development, and stratigraphy. Although quantifying surface roughness differences between alluvial fan units has proven to be difficult in the past, high‐resolution airborne laser swath mapping (ALSM) digital topographic data are now providing researchers with an opportunity to study topography in unprecedented detail. Here we use ALSM data to calculate surface roughness on two alluvial fans in northern Death Valley, California. We define surface roughness as the standard deviation of slope in a 5‐m by 5‐m moving window. Comparison of surface roughness values between mapped fan surfaces shows that each unit is statistically unique at the 99% confidence level. Furthermore, there is an obvious smoothing trend from the presently active channel to a deposit with cosmogenic 10 Be and 36 Cl surface exposure ages of ∼70 ka. Beyond 70 ka, alluvial landforms become progressively rougher with age. These data suggest that alluvial fans in arid regions smooth out with time until a threshold is crossed where roughness increases at greater wavelength with age as a result of surface runoff and headward tributary incision into the oldest surfaces.