AEOLIAN LANDSCAPES - Fundamentals of Geomorphology - page 306

Table 12.3 A classification of dunes

Primary dune forms Criteria for subdivision Secondary dune forms Description

Free Morphology or orientation:

Transverse Transverse Asymmetric ridge

Barchan Crescentic form

Dome Circular or elliptical mound

Reversing Asymmetric ridge with slip faces on either side of

the crest

Linear Seif Sharp-crested ridge

Sand ridge Rounded, symmetric ridge, straight or sinuous

Star Star Central peak with three or more arms

Network Confused collection of individual dunes whose

slip faces have no preferred orientation

(Sheets) Zibar Coarse-grained bedform of low relief and

possessing no slip face

Streaks or stringers or
sand sheets

Large bodies of sand with no discernible dune
forms

Anchored Vegetation and topography:

Topography Echo Elongated ridge lying roughly parallel to, and

separated from, the windward side of a
topographic obstacle

Climbing dune or
sand ramp

Irregular accumulation going up the windward
side of a topographic obstacle

Cliff-top Dune sitting atop a scarp

Falling Irregular accumulation going down the leeward

side of a large topographic obstacle

Lee Elongated downwind from a topographic obstacle

Fore Roughly arcuate with arms extending downwind

around either side of a topographic obstacle

Lunette Crescent-shaped opening upwind

Vegetation Vegetated sand

mounds

Roughly elliptical to irregular in plan, streamlined
downwind

Parabolic U-shaped or V-shaped in plan with arms opening

upwind

Coastal Dunes formed behind a beach

Blowout Circular rim around a depression

Source: Based on Livingstone and Warren (1996, 74-101)

upon the slope of the obstacle. When the upwind slope
of an obstacle is less than around 30 ◦ , sand blows over it.
When it is above 30 ◦ , then sand is trapped and a climb-
ing dune or sand ramp forms. If it exceeds 50 ◦ , then an
echo dune forms at an upwind distance of some thrice the
height of the obstacle. Cliff-top dunes may form in the

zone of slightly lower wind velocity just beyond the crest
of an obstacle. Falling dunes form in the lee of an obsta-
cle, where the air is calmer. If the obstacle is narrow, then
sand moving around the edges may form lee dunes that
extend downwind. Lunettes are crescent-shaped dunes
that open upwind and are associated with pans (p. 299).