Lecture 3 - Drainage Basins

Question 1

Name the four major drainage patterns

Answer 1

Dendritic, Rectangular, Trellis and Radial

Question 2

Describe the Dendritic drainage net

Answer 2

Tree-like, usually occurs on horizontally or uniformly resistant rocks, where there are no structural controls.

Question 3

Describe the Rectangular drainage net

Answer 3

It displays a perpendicular network of streams. Tributaries join the main river at perpendicular angles. It is controlled by joints and fractures

Question 4

Describe the Radial drainage pattern

Answer 4

It has streams heading out in all directions from a central elevated source e.g. a volcano

Question 5

Describe the Trellis drainage pattern

Answer 5

It has a dominant drainage direction. Primary tributaries are perpendicular to the river whereas secondary tributaries are parallel. It is controlled by alternating bands of soft rock.

Question 6

What components control an orogenic drainage net?

Answer 6

• Longitudinal faults predispose drainage along strike;
• Re-entrants along the boundary between the mountain and the basins; they provide the foci for extensive drainage basins