river processes + pressures

What are the 4 main types of transportation (the way river carries eroded material)?

1. Traction — large boulders roll along the river bed

2. Saltation — smaller pebbles bounce along river bed, picked up then dropped

3. Suspension — finer sand is carried along in the flow (river looks brown)

4. Solution — minerals from rocks are dissolved in water and carried along

What is deposition?

When the river loses energy, it may drop some of its load

How do waterfalls form?

1. Band of more resistant rock lies over less resistant rocks

2. Less resistant rock is eroded more quickly

3. More resistant rock is undercut, forming an overhang

4. Overhang can no longer be supported, blocks of rock fall down

5. Waterfall retreats upstream

How do interlocking spurs form?

• The river at its source is small + has limited energy

• Flows around ridges in the valley sides called spurs

• The spurs become interlocking with those on the other side of the valley

How do meanders form?

• On the inside of the bend, current is slower (deposition)

• On the outside of the bend, the current is faster (erosion)

How do ox-bow lakes form?

1. A meander

2. Meander neck narrows

3. Ox-bow lake formed

How is a levee formed?

1. A river floods over its bank

2. The biggest + heavies silt particles can’t be carried and are dropped, forming floodplains

3. Increased deposition on the river bed when the river is low

4. Gradually raises the river bed upwards

5. After many floods, the deposits on the bank build up, forming levées

What are the 4 impacts of climate on river landscapes + sediment loss?

1. Erosion rate is greater where discharge + energy of river are greater

2. Weathering of rocks is greater

3. Amount of discharge is affected by climate (wetter climates = greater discharge)

4. The transportation rate is greater where energy of water is greater

What are the 2 main types of slope processes?

1. Soil creep

   • Particles of soil slowly move down sides of valleys due to gravity

2. Slumping

   • Valley sides are eroded by river, making sides steeper and increasing downward movement of material

What 4 human activities contribute to flooding?

1. Urbanisation

2. Deforestation

3. Land-use change

4. Building on floodplains

What are physical factors that affect lag time?

• Geology

• Soil type

• Vegetation

• Slope

What are 2 hard engineering methods and their advantages + disadvantages?

1. Embankments

   • Uses natural materials (attractive)

   • May burst, causing flooding

2. Flood walls

   • Requires minimal maintenance

   • Blocks view of the river

What are 2 soft engineering methods and their advantages + disadvantages?

1. River restoration

   • Can reduce flooding downstream

   • People living there might not want land use to change

2. Plant trees

   • Increased infiltration

   • Not suitable for all locations

Why does increased discharge increase erosion?

Increases load (1) which increases abrasion (1)

2 reasons for why employment of women has increased?

1. Having fewer children, so available to work

2. Population has grown