River Processes and Pressures

Question 1

what is hydraulic action?

Answer 1

the force of the water on the bed and banks of the river removes material

Question 2

what is attrition?

Answer 2

the load that is carried by the river bumps together and wears down into smaller smoother pieces

Question 3

what is abrasion?

Answer 3

material carried by the river rubs against the bed and banks and wears them away

Question 4

what is corrosion/solution?

Answer 4

some rock minerals dissolve in the river water

Question 5

what are the four main types of transportation?

Answer 5

traction
saltation
suspension
solution

Question 6

what is traction?

Answer 6

large boulders roll along the river bed

Question 7

what is saltation?

Answer 7

smaller pebbles are bounced along the river bed, picked up and then dropped as the flow of the river changes

Question 8

what is suspension?

Answer 8

finer sand particles are carried along the river giving a brown appearance

Question 9

what is solution?

Answer 9

minerals from rocks such as limestone and chalk are dissolved in water and carried along the river

Question 10

what is transportation?

Answer 10

the way in which the river carries eroded materials

Question 11

what is deposition?

Answer 11

the river slowing down and dropping some of its load

Question 12

what is a waterfall?

Answer 12

a steep drop ion a river’s course

Question 13

how are waterfalls formed?

Answer 13

• a band of resistant rock lays over less resistant rock
• less resistant rock underneath erodes forming an undercut and an overhang
• the overhang can no longer be supported so rocks fall
• the powerful fall of water erodes a plunge pool

Question 14

what are interlocking spurs?

Answer 14

water flows naturally from side to side of a valley around ridges called spurs which interlock at the other side of the valley

Question 15

what are meanders?

Answer 15

bends in the river course

Question 16

how are meanders formed?

Answer 16

the river swings one way and the other causing erosion on the outside bends

Question 17

how are floodplains formed?

Answer 17

the river deposits sediment on the outside bends after flooding as heavier particles cannot be carried back into river by water

Question 18

how is an oxbow lake formed?

Answer 18

the neck of a meander narrows cutting it off from the rest of the lake

Question 19

what are levees?

Answer 19

the build up of floodplains

Question 20

what are deltas?

Answer 20

a flat area of land created by a build up of sediment

Question 21

how are deltas formed?

Answer 21

the speed of a river decreases as it approaches the sea so it deposits some of the material it is carrying

Question 22

how does climate impact transportation rate?

Answer 22

rivers in wet climates transport more material than those in dry climates

Question 23

how does climate impact weathering processes?

Answer 23

freeze thaw weathering more likely to occur in cold climates

Question 24

how does climate impact average amount of discharge?

Answer 24

wetter climates mean more discharge than hotter climates where discharge evaporates

Question 25

how does climate impact erosion rate?

Answer 25

rivers in wet climates have a greater erosion rate

Question 26

what is soil creep?

Answer 26

particles of soil move slowly down the sides of valleys under the influence of gravity

Question 27

what is slumping?

Answer 27

valley sides are eroded by the river making the sides steeper and increasing the downward movement of material

Question 28

what is the lag time on a storm hydrograph?

Answer 28

the difference in time between peak rainfall and peak river discharge

Question 29

what does a storm hydrograph show?

Answer 29

how a river responds to a rainstorm

Question 30

what does the line on a storm hydrograph show?

Answer 30

the discharge in metres cubed per second

Question 31

what do the bars show on a storm hydrograph?

Answer 31

the amount of rainfall measured in millimetres

Question 32

how does geology make lag time short, the rising and falling limbs steep and discharge high on a storm hydrograph?

Answer 32

more resistant rock will will absorb less water than less resistant rock so run off will be greater and faster

Question 33

how does soil type make lag time short, the rising and falling limbs steep and discharge high on a storm hydrograph?

Answer 33

more impermeable soils will absorb less water than permeable soils so surface run off will be greater and faster

Question 34

how does vegetation make lag time short, the rising and falling limbs steep and discharge high on a storm hydrograph?

Answer 34

plants use water so run off will be greater and faster on the ground where there is less vegetation

Question 35

how does slope make lag time short, the rising and falling limbs steep and discharge high on a storm hydrograph?

Answer 35

steeper slopes cause faster surface run off so more water reaches the river quicker

Question 36

how does drainage basin shape make lag time short, the rising and falling limbs steep and discharge high on a storm hydrograph?

Answer 36

a wide basin with a lot of tributaries close together means water enters the river faster

Question 37

how do antecedent conditions make lag time short, the rising and falling limbs steep and discharge high on a storm hydrograph?

Answer 37

when the ground is already saturated further water will run off into the river quicker

Question 38

what is the water shed in the river basin?

Answer 38

the area of high land forming the edge of a river basin

Question 39

what is the source in the river basin?

Answer 39

where the river begins

Question 40

what is the mouth in the river basin?

Answer 40

where a river meets the sea

Question 41

what is the confluence in the river basin?

Answer 41

the point at which two rivers meet

Question 42

what is the tributary in the river basin?

Answer 42

a small rivers or stream that joins a larger river

Question 43

what is the main river channel in the river basin?

Answer 43

the main area through which the river flows

Question 44

what is the drainage basin in the river basin?

Answer 44

the area of land drained by a river

Question 45

what is interception?

Answer 45

water being prevented from reaching the surface by trees of grass

Question 46

what is the watertable?

Answer 46

current upper level of saturated rock/soil where no more water can be absorbed

Question 47

what is infiltration?

Answer 47

water sinking into the rock/soil from the ground surface

Question 48

what is groundwater flow?

Answer 48

water flowing on top of the ground

Question 49

what is percolation?

Answer 49

water seeping deeper below the surface

Question 50

what is throughflow?

Answer 50

water flowing through the rock layer parallel to the surface

Question 51

what is transpiration?

Answer 51

water lost through pores in vegetation

Question 52

what is surface run off?

Answer 52

water flowing through the soil layer parallel to the surface

Question 53

what is evaporation?

Answer 53

water lost through round/vegetation surface

Question 54

how does deforestation increase flooding?

Answer 54

prevents interception so there is more surface run off

Question 55

how does land use change increase flooding

Answer 55

rates of transpiration, erosion and deposition will slow | no trees to stop interception

Question 56

how does urbanisation increase flooding?

Answer 56

more impermeable surfaces like concrete prevent infiltration

Question 57

what are flood walls?

Answer 57

artificial barriers built along a river to raise height or river channel to increase capacity

Question 58

what are embankments?

Answer 58

artificial levees to raise height of river channel and increase rivers capacity

Question 59

what are flood barriers?

Answer 59

gates built near the river mouth which close during storm surges

Question 60

what is floodplain retention?

Answer 60

maintaining the rivers original landscape by lowering the level of floodplains or planting grass and trees

Question 61

what is river restoration?

Answer 61

restoring a rivers original features like meanders to slow water velocity