RIVERS : Stages of a River
RIVERS
A river is a natural flowing water course usually freshwater, flowing towards an ocean, a lake, a sea, or another river.
River Bank: Two sides of a river called River banks.
Rivers have two banks: Right
bank and Left bank.
If you stand on a river and face the way the water is flowing,
the right will be on your right hand side and left bank will be on your left
hand side.
River bed:
The bottom of the river
called River bed. It can be made up of stones, pebbles, boulders, rock and mud.
The water flows over the river bed. Rivers bed can be seen in streams because
of its shallow water. River bed of middle and lower course is not visible
because of deeper water.
River Channel: The main way or the path by which river water
flow is called the river channel. It can be a straight channel like a canal or
a meandering channel. Channel gives the river its shape.
Courses of Rivers: Rivers have three courses:
Upper course
Middle course
Lower course
Upper course: The upper course found in the mountains and
hills where the river starts its journey. Waterfalls, rapids are found in this
course. The river starts as a stream in the upper course and flows through
V-shaped valleys. The river has fast flowing water in the upper course. Rivers
carry lots of stones and boulders with the water to flow over. Fast flowing water
and grinding stones cut down the river valley and make the river valleys deeper
and steeper in
upper course. Erosion occurs mostly here.
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| Rivers in upper course |
Middle course: The middle course is where the river starts to
become wider and deeper. Instead of eroding downwards river starts erode sideways.
This creates a broad V-shaped valley. The river starts to meander or bend in
the middle course. River flows gently here. Erosion and deposition occurs in
this course.
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| Rivers in middle course |
Lower course: Rivers flow slowly in this course. Rivers
become widest here. This course is found closest to the sea where the river has
its mouth. The flat area beside the river banks is known as floodplain.
Floodplain is very fertile because of its alluvial soil. Farmers grow crops there.
Sometimes river might also have Estuary or Delta at its mouth.
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| Rivers in lower course |
Stages of Rivers: There are also three stages of a river’s life:
Stage 1 is a youthful river. This is the rivers upper
course where the rivers have fast flowing water, rapids, stream and
tributaries.
Stage 2 is the mature river. This is the river in its
middle course where it has meanders and flowing gently.
Stage 3 is the river in old age. This is in lower
course, where rivers flow slowly towards its mouth at the sea.
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| Features of a river |
Source:
Source is the start or beginning of a river.The source of a river usually found in hills and mountains.A river can have more than one source.Sources can be different type:
Springs:Some rivers begin where water flows out of rocks.Rain water sinks through the soil and trickles through the cracks and spaces in rocks such as chalk and limestone.These are called Permeable rocks.The water continues to do this until it reaches a rock like clay.Clay is an impermeable rock.
Rills and Streams:Lots of rain fall on mountains.Rainwater flows down slopes and quickly makes channels.At beginning channels are small . They are called They are called Rills.They join together and make bigger rills . Finally stream is formed.The streams join up to make a river.
Lakes:The source of some rivers are Lakes. The source of river Nile is Lake Victoria in Burundi.
Melting Snow and ice:When the weather gets warmer the snow and ice melts.This forms lake in front of glaciers and rushes into channels in the V-shaped valley and eventually forms a river.
Few examples of sources of rivers:
The source of river Nile is Lake Victoria in Burundi.
The source of Missouri river is in Rocky mountain.
The source of Amazon river is in Andes mountains.
Stream
A stream is the same as a river. Streams usually have narrow
channels and are quiet shallow. Streams are usually found in the upper courses.
Tributary:
A tributary is a stream or a river flowing into a larger river.
A river grows as more tributaries flow into it. There is no special size that a
tributary has to be. Some of the World’s longest river are joined by
tributaries that themselves are major rivers. Example is Missouri river a major
tributary of the Mississippi river.
Mouth:
Mouth is the place where river ends its journey.Rivers may meet the sea, a lake or a larger waterway.Most rivers flow into the sea.
Not all rivers mouth are the same.There may be an Estuary or Delta at the mouth.The River Jordan flows into the dead sea which is actually an inland lake.In desert areas some rivers simply dry up.
Estuary:
If the river has wide mouth, it is called an Estuary.Rivers carry a lot of sediment as it travels from its source to its mouth.When the freshwater from the rivers meet the salty water from the sea , the river drops its sediment.Most is then washed away by the sea and the tides.
