fluvial processes

Question 1

fluvial systems

Answer 1

• distributed network operating from very small to very large scale
• comprise physical and living
• transport water and sediments from areas of erosion to deposition

Question 2

hydrological cycle

Answer 2

This is how water moves between reservoirs on the Earth. Without the cycle there would be no oceans, rivers, groundwater or life on earth.

Question 3

surface water

Answer 3

flows occur when soils are saturated or when the rain is so heavy it cannot infiltrate the soil.

Question 4

explain what hillslope-fluvial couple means?

Answer 4

water flows from the hills into the stream

Question 5

overland flow

Answer 5

excess water from rainfall or snowmelt runs across the surface and can deliver large amounts of sediment

Question 6

Drainage basin

Answer 6

• distributed channel network which eventually converge into a single channel
• drainage basin is an area from which a river or stream and their tributaries carry all the surface runoff

Question 7

what separates drainage basins?

Answer 7

topographic highs, which are referred to as watersheds or divides

Question 8

shape of a drainage basin affects its response to the catchment. How would dendritic basins compare to long narrow basins in a rainfall?

Answer 8

dendritic basins would respond quickly, long and narrow would be a slower response

Question 9

whats it called where two 1st order streams meet?

Answer 9

2nd order stream

Question 10

if a 3rd order stream meets a 1st order stream, what results?

Answer 10

still 3rd order

Question 11

4th order stream occurs when?

Answer 11

two 3rd order streams meet

Question 12

what is the main thing that influences stream velocity?

Answer 12

river gradient. higher = faster velocity. faster velocity = more erosion

Question 13

ultimate vs local base level

Answer 13

• ultimate base level is the ocean because rivers flow into the ocean so they cant erode any lower than that.
• Local or temporary base levels may occur e.g. if there is a lake half way down the mountain the river is flowing down.

Question 14

how does turbulence affect river velocity? where about is the greatest velocity of the river?

Answer 14

decreases it.

highest velocity in the middle of the surface.

Question 15

greatest turbulence occurs where?

Answer 15

bed of the channel

Question 16

3 types of sediment load in a river

Answer 16

1. dissolved load (from chemical weathering)
2. suspended load (silt and clay)
3. bed load (larger sand and gravel)

Question 17

when will you get a braided stream? (one of those capillary bed looking things)

Answer 17

braided streams are streams which have too much sediment and deposit sand and gravel bards in their channels

Question 18

what is a meandering stream?

Answer 18

single sinuous channel with looping curves known as Meanders.

Question 19

Outer bank of a meander is called? inner bank is called?

How does the erosion compare?

Answer 19

outer bank is called cut bank and has the highest velocity, so there is erosion.
inner bank is called the point bar and is the site of deposition.

Question 20

over time what happens to meandering streams?

Answer 20

the loops become larger and larger as the cut banks shrink and the point bar grows

Question 21

floodplain

Answer 21

broad strip of land built up by sedimentation on either side of the stream/channel. Called a floodplain because in a flood they may become covered in water with suspended clay and silt

Question 22

Delta

Answer 22

A delta forms when a running body of water enters another body of water and the running body of water slows and deposits its sediment which builds up a local, prograde shore line as a result

Question 23

alluvial fan (whats a colluvial fan?)

Answer 23

large fan-shaped pile of sediment that forms when a streams flows through a gully onto a flat plain and its velocity slows and its sediment is deposited.
Its called a colluvial fan if its formed from debris flow.

Question 24

when will a flood occur?

Answer 24

when the streams or rivers receive more water than their channel can handle

Question 25

coastal flood

Answer 25

caused by wind-generated waves and storm surges

Question 26

urban flood

Answer 26

Urbanisation has removed the infiltration capacity of the soil. Backed-up storm sewers are common causes

Question 27

urban hydrograph

Answer 27

building, concrete and asphalt have removed the infiltration capacity of the soil.
Surface runoff increases

Question 28

4 flood mitigation measures

Answer 28

1. Dam -capture and slowly release the extra water
2. levees - artificially deepen the water
3. floodways - add extra channels to deal with larger volumes
4. floodwall - wall protects low lying areas of the town

Question 29

All things being equal the channel with the lowest wetted perimeter will have the _______ water velocity

Answer 29

greatest