Geography

Firstly, I want to introduce my Geography teacher , Tashi Wangdi sir.  He is from Pema Gatshel but he is teaching a student in my school Udzorong Central School. I like the way he teaches us in class and I am proud to say that I am a student who’s studying geography under Tashi Wangdi sir. He is not only my teacher this year but also my teacher forever. In Today's class I learnt River.

A river begins from mountains or hills and flows down to low land. In a cold region, a river may originate from melting snow or a glacier. In warmer places, water drains from slope to form channels during rainfall. These channels join together to form stream and river.

The impact of river on the physical landscape is understood through the study of different stages. These stages are divided into upper, middle and lower based on the flow of water.

The works of river.

i) Erosion

It is the removal of materials from the Earth’s surface. The erosional work of a river depends on channel gradient, volume of water, river load and velocity.

ii) Transportation

River transport the eroded materials from higher gradient to lower gradient. The transportation capacity is determined by size and amount of load, volume and velocity of a river.

iii) Deposition

Deposition of loads take place as the river enters the low lying areas. It is due to decrease in gradient and velocity of river.

In todays class I learnt Stages of River.

Stages of River.

1.Upper Course or Youthful Stage

Rivers are usually small and flow down with lots of energy due to steep gradient. The features formed in this stage are formed by erosional work. The main work of a river in this stage is vertical erosion or downward cutting. Some of the land features formed are V-shaped valleys, gorges, interlocking spurs and waterfalls.

2.Middle or Mature stage

In this stage, the river flows through gentle slope. The volume of river increases with increase in number of tributaries. The speed of the river decreases due to decrease in slope. River erodes side wards and it is called lateral erosion. Transportation is the main work while some deposition also takes place. The main land features formed in this stage are alluvial fans, broad valleys and meanders.

3.Lower or Old stage

In this stage the speed of the river decreases mainly due to low gradient. The volume of water also increases. The main work in this stage is deposition. Some of the features are meanders, oxbow lakes, flood plains and natural levees.