Draw (terrain)

A draw, sometimes known as a re-entrant in orienteering, is a terrain feature formed by two parallel ridges or spurs with low ground in between them.^[1] The long area of downward sloping low ground itself is the draw, and it is defined by the spurs surrounding it.

Example on a topographical map, and how it would look in the real world.

Typical draw, Little Carpathians

Characteristics

Draws are usually etched in a hillside by water flow, are usually dry, but many contain an ephemeral stream or loose rocks from eroded rockfall. In a draw the ground always slopes downward in only one direction, and upward in the other three.^[2][3] The slope on a draw is generally quite sharp, with a clearly established fall line and characterized by a generally steep vertical drop over a short horizontal distance. There is essentially no level ground and little or no maneuver room within the draw. On a topographical map, the contour lines depicting a draw are U-shaped or V-shaped, pointing toward high ground.

A draw can be conceptually thought of as the inverse of a spur, much how a valley can be considered the inverse of a ridgeline. In land navigation training, students are typically taught to visualize these features by making a closed fist with their hand; the knuckles form "hills" individually (and a ridgeline collectively), and from there the fingers represent spurs while the gaps in between fingers represent draws.^[4]

Comparison with valleys

Draws are less developed stream courses than valleys, and are similar to valleys on a smaller scale; however, while valleys are by nature parallel to a ridgeline, a draw is perpendicular to the ridge, and rises with the surrounding ground, disappearing up-slope.^[5] In some cases, a draw could be considered as the initial formation of a valley.^[6]

Etymology

The term "draw" has almost completely supplanted usage of "re-entrant" in common parlance; apart from a few geologists, only orienteers regularly use latter term.^[7]

See also

• Arroyo (watercourse) – Dry watercourse with flow after rain
• Canyon / Gorge – Deep chasm between cliffs
• Chine – Steep-sided river valley
• Couloir – Steep, narrow mountain gully
• Defile (geography) – Narrow pass or gorge between mountains or hills
• Gully – Landform created by running water and/or mass movement eroding sharply into soil
• Mountain pass – Route through a mountain range or over a ridge
• Riparian zone – Interface between land and a river or stream
• Salient (military) – Battlefield front breakthrough progressing into enemy territory
• Transverse valley – Low-lying area deeply interrupting a mountain chain
• Wadi – River valley, especially a dry riverbed that contains water only during times of heavy rain