River - River Processes

River - Factors Affecting Energy of Rivers

River - Case Studies for River Management

River - Drainage Pattern

River - Why is There No Delta At the River Mouth?

River - Negative Impacts of Channelisation

River - Vertical & Lateral Erosion

River - Channelisation

River- Positive and Negative Impacts of Rivers

River- Transportation

River- Erosional Processes

River Features- Delta

River Features: Animation- Formation of Waterfall

River Features- Ox-bow Lake

The following webpage shows an animation of how an oxbow lake is formed.
http://www.school-portal.co.uk/GroupDownloadFile.asp?file=21606

River Features- Cross Section of Meander

River Features- Meander

River Features- Floodplain & Leeves

River Features- Waterfall

River Processes

There are 3 river processes that occur as the river flows along its course.

1) Erosion
occurs when rocks and other materials are broken into smaller pieces and moved downstream by the energy of the river.

The four processes of erosion are:

• Hydraulic action where fast-moving water loosens and dislodges the rocks and soil from river bed and banks.
• Corrasion where rock fragments that are dragged along by the flow of the river, grind against the river bed and banks.
• Attrition where eroded materials in the river constantly collide against each other and break down into smaller pieces.
• Solution where minerals in the rock dissolve in the carbonic acid in the river due to acid rain.

To remember:
" I was a piece of rock by the river bank, broken off by hydraulic action. I was carried by the river causing corrasion as I erode the river bed and banks. I collide against the other rocks, resulting in attrition. I’m going to be dissolved in solution as there’s carbonic acid in the water. "

(By student: Hot Chicks Affect Success)

2) Transportation
occurs when materials are carried downstream by the energy of the river.

The four processes of transportation are:

• Traction where the larger size materials are rolled and slided along the river bed. (e.g boulders and gravel)
• Saltation where materals are transported downstream in a series of bouncing action. (e.g. coarse sand)
• Suspension where fine particles are carried along in the river without touching the river bed. (e.g. silt and clay)
• Solution where the river transport dissolved materials downstream. (e.g. calcium carbonate)

The following webpage shows an animation of how the river transports its load.
http://www.school-portal.co.uk/GroupDownloadFile.asp?file=21393

To remember:
" There was a tractor (traction) bringing soil to the construction site. However the salt (saltation) content of the soil is too high. The driver got a suspension and has to think of a solution as he lost his rice bowl. "

(By student: Think Some Sexy Stuff)

3) Deposition
occurs when the river puts down or deposits its load due to insufficient energy.

Energy of the River

The energy of the river is determined by 2 factors- speed of flow and volume of water. Therefore, when the speed of flow and the volume of water is high, the energy of the river is also high. We say that there is a positive relationship between energy of river and the speed of flow and the volume of water that the river is carrying.

There are 3 factors affecting the speed of the river. (GRoW)
1) Gradient of channel
Rivers flow downhill from a height due to gravity. Therefore, a steep gradient will cause the speed of the river to be fast.

2) Roughness of channel
A smooth channel without obstacles like rocks and boulders will increase the speed of the river.

3) Wetted perimeter
The lesser the water that contact the river channel, the higher the speed of flow due to less friction.

There are 4 factors affecting the volume of water in the river. (SPCPetrol)
1) Size of Drainage Basin
The larger the drainage basin, the higher the volume of water of the river.

2) Presence of Vegetation
More vegetation will result in higher interception and lower runoff, resulting in lower volume of water. Vegetation will also delay the amount of water that reaches the river in a short time, preventing floods.

3) Climate
If the rainfall is high, the river will have a higher volume of water.
Climate will also determine the amount of vegetation in the river vicinity.

4) Permeability of Rocks
High premeability will result in low volume of water due to decrease in runoff.