River Process

Question 1

What determine the speed of river?

Answer 1

Gradient

roughness of Channel

Wetted perimeter.

Question 2

How does the roughness of channel affect the river speed?

Answer 2

Boulders or pebbles or rocks are obstacles which make the river use more energy to overcome the friction of the channel. Thus the velocity is reduced.

Question 3

How does gradient affect the speed of river?

Answer 3

The steeper the gradient, the faster the river flows

Question 4

How does the wetted perimeter affect the speed of the river?

Answer 4

The longer the wetted perimeter, the larger the surface area the water will contact with the channel. More friction thus need to be overcome. Hence the speed is reduced.

Question 5

What are the factors affect the volume of a river?

Answer 5

1. Drainage basin
2. Presence of vegetation
3. Permeability of rocks.
4. Climate

Question 6

How does the drainage basin affect the volume of the river?

Answer 6

The bigger the basin, the greater will be the amount of water within the river. Catchment area I’d larger, more tributaries.

Question 7

How does the presence of vegetation affect the river volume?

Answer 7

With more vegetate present, more water will be intercepted.

This allows the water to infiltrate and percolate and be stored as ground water.

Hence, less surface runoff.

Question 8

How does permeability of rocks affect the volume of river?

Answer 8

An area with permeable rocks will allow water to infiltrate into the ground and this results in less surface runoff.

Question 9

How does climate affect the volume?

Answer 9

During dry season: higher temperature, less rainfall

During wet season: lower temperature, more rainfall

Question 10

What are the two general types of erosion? Where do they commonly occur?

Answer 10

Vertical erosion - upper course

Lateral erosion - lower course

Question 11

What are the four typical types of erosional processes?

Answer 11

Corrasion / abrasion
Attrition
Solution
Hydraulic action

Question 12

Talk about how does corrasion erode the river channel?

Answer 12

1. Rock fragments carried along by the river are capable of grinding against the river bed and banks of its channel.
2. The rocks chip away at the channel, causing it to be widened and deepened
3. It’s particularly effective during periods of floods where the river velocity and force are at its maximum.

Question 13

Talk about how does the attrition erode the channel.

Answer 13

1. The river carries a load of eroded materials which contains rock fragments and other materials.
2. These materials and fragments constantly collide with one another as they move.
3. Over time, they are broken down into smaller pieces and their rough edges may be smoothened out.

Question 14

Talk about how does solution take place as an erosional process.

Answer 14

1. As rain falls onto the earth, it interacts with the carbon dioxide present in the atmosphere .
2. As a result, the rainfall becomes a form of weak carbonic acid.
3. The rainwater hence can dissolve certain minerals present in the rocks on the river bed and banks.

Question 15

Talk about hydraulic action.

Answer 15

1. This action’s erosive agent involves the force of running water.
2. In a high-energy river, the water is capable if loosening the rocks and dislodging them from the river bed and banks.
3. This process erodes the river channel by removing rocks which protrude from the river bed and banks.

Question 16

Which types of processes are involved in transportation?

Answer 16

Traction
Saltation
Suspension
Solution

Question 17

List the sizes of sediments.

Answer 17

Clay 
Silt 
Sand
Pebbles 
Cobbles
Boulders

Question 18

How is a water fall formed due to erosion of unequal resistance of rocks.

Answer 18

1. A river may flow an area covered with rock layers of different resistance
2. The river will erode the less resistant layers more rapidly.
3. The differential rate of erosion will result in a change of gradient along the less resistant layers
4. Over a time, water will plunge from great heights to hit the river bed wish a great amount of force.
5. Repeated pounding of the river bed by the plunging waters may leave a depression at the base of the waterfall.
6. This depression is deepened as rocks and boulders swirl around, cutting into the river bed. The resultant pool is known as a plunge pool.

Question 19

How is the water fall formed due to faulting?

Answer 19

1. Faulting involves the displacement of rocks.
2. This displacement may result in one block of land lifted higher Than the other.
3. when a river flows down from the edge of the uplifted block to the lower block, a waterfall and plunge pool are formed.

Question 20

How is a gorge formed?

Answer 20

1. When river flows through an area of resistant rocks, it can only carry out vertical erosion, leaving the sides relatively unaffected.
2. Over a time, deep, narrow and steep-sided valley know as gorge is formed