PHOTO PATTERN DATA ELEMENTS: ALLUVIAL FAN
The Basin and Range Province- This desert region is an area characterized by blockfaulted mountains and adjacent basins, some below sea level. Sediments flow off the
tilted blocks and form sloping, layered deposits of coarse-to-fine alluvium. Erosion
causes troughs to form in the surface of these layered deposits. (Arid)
Form
Fan, series of fan-shaped deposits sloping to a valley along
a mountain front. The materials grade from gravel to sand
to silt downslope.
Drainage
Dendritic where developed- drainage absent on most
deposits.
Gully Characteristics
Sharp, V-shaped gullies with steep gradients.
Special Features
Coalescing fans form almost continuous sloping surface.
Color (Photo Gray Tones)
Light grays indicate sorted granular materials. Dark pattern
due to vegetation.
Land Use
Agriculture developed on the porous fans. Wind erosion
occurs if vegetation does not anchor the soil.
Vegetation
Plants are restricted to area containing porous materials
which have groundwater.
Source: Terrain analysis procedural guide for surface configuration, US Army engineer
topographic laboratories, p. 7-43