O Level Notes : Geography - landforms and landscape processes - The course of the river
To understand river processes and landforms it is important to start by looking at the course of the river. The course of the river is the stretch of the river from its source through the middle course to the mouth. This is also called the river's long profile.
The Course of the river
The source of the river is where the river starts. Usually these sources are in highlands or wetlands which supply the river with water. The middle course is the central segment of the river and the mouth is the lower part of the river where the river enters the sea or lake. Despite understanding the course of the river, it is also important to know the features of the cross sections of the rivers.
The River Cross Section
The banks are the sides of the channel. The width is the distance across the channel from one bank to another. The bed of the river is the floor of the river while the depth is the distance from the water surface to the bed. There are also other features that you need to understand. These include the following:
Velocity
It is the speed of the river or water flowing in the channel. This speed varies from one part of the channel to another.
Velocity variations
- Cross sectional area
It is the area across the channel from one bank to another. It is the area covered by the channel across a given point along the course of the river.
- Tributaries
These are streams which join the other bigger streams.
- Distributaries
These are small channels branching away from the main river. (These channels branches off and flows away from the main stream.)
- Confluence
The point where two streams join.
- Types of Flow
The water shows different patterns as it flows down the channel. The types of Flow are:
- Laminar flow
This pattern of flow occurs where velocity is low. It is the smooth horizontal flow of water. The low velocity allows water to flow in sheets or laminar. It is rare because channels are not generally smooth.
Laminar Flow
- Turbulent Flow
It is the rough flow of water down the channel. This pattern is common when velocity is high and the channel is meandering. The rough channel bed especially in mountainous regions lead to turbulent flow of water. The water hits boulders and the rough bed experience eddies which is the swirling of the flowing water.
Turbulent flow of water
- Helicoidal Flow
This is the corkscrew motion of water. Pools and rifles on the bed of the river causes the water to follow a corkscrew flow.
Helicoidal Flow
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