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Drainage Pattern
Drainage pattern is defined as a general layout or arrangement of the main river and the tributaries on the surface of the earth. It can also be defined as the way in which the tributaries join the main river.
A drainage pattern describes the characteristic way tributaries and rivers branch off in different directions. The most common drainage pattern is called dendritic.
A dendritic drainage pattern, which resembles the shape of a tree, tends to develop where a whole drainage basin is made up of the same type of rock.
A rectangular drainage pattern is made of numerous cracks that form a grid pattern; this pattern is common over certain types of rock, such as granite, in which cracks called joints develop to form a grid.
Radial drainage patterns occur where rivers flow in all directions away from a raised feature, such as a volcano.
Centripetal drainage is found where rivers flow from surrounding high ground toward a central basin, which is often occupied by a lake.
Some of the most complex drainage patterns are found in areas where erosion of folded beds of strata has produced parallel bands of alternating softer and harder rocks. In such cases the rivers cut parallel valleys in the softer strata, with short steep tributaries flowing down at right angles from the ridges of harder rock.
In a few places the rivers may cut across the hard rock bands and connect the major parallel river channels. This type of drainage is called a trellis drainage pattern.
Activity
Study the big rivers on the Atlas.
1. In which highland do they rise?
2. Which rivers flow through most countries? Name these countries.
3. Which rivers flow through deserts or semi-desert? Name these dry areas.
4. Rivers often form borders between countries, can you find some examples.
1. In which highland do they rise?
2. Which rivers flow through most countries? Name these countries.
3. Which rivers flow through deserts or semi-desert? Name these dry areas.
4. Rivers often form borders between countries, can you find some examples.