Define the following drainage patterns:
Dendritic
Trellis
Rectangular
Radial
Answers
A radial drainage pattern occurs when the tributaries flow radially outward and downward from a central topographic high. This type of pattern is typical of volcanic cones, isolated hills, and elevated domes.
Definition of rectangular drainage pattern. A drainage pattern in which the main streams and their tributaries display many right-angle bends and exhibit sections of approx. the same length; it is indicative of streams following prominent fault or joint systems that break the rocks into rectangular blocks.
rellis drainage pattern occurs where subparallel streams erode a valley along the strike of less resistant formations. These beds are usually steeply dipping and may be part of a fold system. The tributaries often intersect at right angles where a notch called a water gap cuts through a harder formation.
The main types of drainage patterns:
Dendritic patterns, which are by far the most common, develop in areas where the rock (or unconsolidated material) beneath the stream has no particular fabric or structure and can be eroded equally easily in all directions. Examples would be granite, gneiss, volcanic rock, and sedimentary rock that has not been folded. Most areas of British Columbia have dendritic patterns, as do most areas of the prairies and the Canadian Shield.
Trellis drainage patterns typically develop where sedimentary rocks have been folded or tilted and then eroded to varying degrees depending on their strength. The Rocky Mountains of B.C. and Alberta are a good example of this, and many of the drainage systems within the Rockies have trellis patterns.
Rectangular patterns develop in areas that have very little topography and a system of bedding planes, fractures, or faults that form a rectangular network. Rectangular drainage patterns are rare in Canada.