Own Knowledge - Rivers

Question 1

types of weathering

Answer 1

physical - freeze thaw
chemical - acid rain
biological - roots of plants

Question 2

types of mass movement

Answer 2

sliding
rock fall
slumping

Question 3

types of erosion

Answer 3

hydraulic action - sheer force of the water
abrasion - material carried by the river being rubbing against banks and bed of the channel, wearing it away
solution - minerals dissolve into water - slightly acidic - dissolve rocks
attrition - sediment particles collide with each other - rounder and smaller

Question 4

types of transportation

Answer 4

traction - rolling along river bed
saltation - bounce over eachother on the river bed
suspension - the water flow carries silt and clay-sized particles
solution - river water dissolves some minerals

Question 5

how do interlocking spurs form

Answer 5

• upper course
• erode downwards
• flow around the hardest parts of the rocks

Question 6

how do waterfalls form

Answer 6

• band of hard more resistant rock lies over a band of soft rock
• river erodes less resistant rock at a faster rate - undercutting it
• eroded by hydraulic action and abrasion
• hard rock overhangs
• hard rock falls under force of gravity
• falling rocks cause erosion of the river bed and the formation of PLUNGE POOL
• gorge forms as waterfall retreats = soft rocks eroded and hard collapses - gorges form in hard rock where vertical erosion is dominant

Question 7

how do meanders form

Answer 7

• found in flood plain
• highest velocity on outside of the bend - lateral erosion
• forms a RIVER CLIFF
• inside of bend - velocity less - deposition
• forming a POINT BAR

Question 8

how do oxbow lakes form

Answer 8

• rivers erode outside of bend fastest
• narrows the neck
• eventually erodes through neck
• new river by passes the meander
• dries up leaving an oxbow lake

Question 9

how is a flood plain formed

Answer 9

• formed by both erosion and deposition
• lateral erosion on outside of bends of meanders means they MIGRATE across valley floor + erode Vally sides = valley floor becoming wide and flat
• during floods - flood water spreads across valley floor + deposit fine sediments called ALLUVIUM as it loses energy - flat land

Question 10

how do levees form

Answer 10

• natural embankments of sediment on either side of a river
• during a flood water come out of channel and lose velocity
• deposits the larger + heavier material first on its bank
• repeated flooding causes these banks to get higher - forming levees

Question 11

how do deltas form

Answer 11

• when rivers meet another body of watet eg. ocean - loses velocity + deposits sediment
• if river deposits faster than it erodes = sediment builds up in a fan-shaped DELTA

Question 12

how does width change from source to mouth

Answer 12

• increases

Question 13

how does depth change from source to mouth

Answer 13

increases

Question 14

how does velocity change from source to mouth

Answer 14

increases

Question 15

how does discharge change from source to mouth

Answer 15

increases

Question 16

how does gradient change from source to mouth

Answer 16

decreases

Question 17

how does channel roughness change from source to mouth

Answer 17

becomes smoother = less friction

Question 18

how does sediment size change from source to mouth

Answer 18

becomes smaller + rounder

Question 19

define lag time

Answer 19

the difference between peak rainfall and peak discharge

Question 20

flashy hydrograph

Answer 20

• steeper rising limb
• short lag time
• higher peak discharge

Question 21

subdued hydrograph

Answer 21

• gentler rising limb
• longer lag time
• lower peak discharge

Question 22

how does drainage size and shape affect hydrograph

Answer 22

• small, elongated = higher discharge

- circular = lower discharge

Question 23

bridging points on river severn

Answer 23

Shrewsbury

Question 24

antecedent conditions - river severn 2007

Answer 24

140mm - highest in 100 years

Question 25

why is the risk of flooding increasing

Answer 25

- increasing population = building on floodplains - changes to land use = urban development creates more impermeable surfaces - changes to weather patterns = climate change

Question 26

Tewksbury damage

Answer 26

- 4800 homes affected - each home had estimated repair cost of 20,000 - 30,000 pounds - local council - 140,000 pounds

Question 27

who is responsible for managing the risk of flooding

Answer 27

environment agency

Question 28

how does the environment agency reduce chance of flooding

Answer 28

catchment management = rating the risk of properties | hard + soft engineering

Question 29

hard engineering strategies

Answer 29

- flood walls - embankments - flood barriers building infrastructure to overcome challenges

Question 30

advantages and disadvantages of embankments

Answer 30

- high banks built on or near a river / man made levees advantages - stop water from spreading into areas where it could cause problems - eg. settlements - they can be earth and grass - which blend into environment disadvantage - flood may go over the embankments - can burst under pressure, causing even greater damage

Question 31

advantages and disadvantages of flood walls

Answer 31

artificial barriers designed to raise the height of river banks advantages - increases capacity + prevent water from spreading disadvantages - expensive to build - may cause flooding downstream - ugly

Question 32

advantages and disadvantages of demountable flood barriers

Answer 32

a temporary structure that is only installed when needed advantages - put up and taken down when needed - prevent so much ugliness disadvantages - may not be installed in time

Question 33

advantages and disadvantages of permanent flood barriers

Answer 33

flood gates built near the river mouth to prevent a storm surge form flooding advantages - gates can be closed when a high surge is forecasted - able to protect large areas disadvantage - high cost - ugly

Question 34

examples of soft engineering

Answer 34

- flood plain retention - river restoration working with nature to encourage natural processes

Question 35

advantages and disadvantages of flood plain retention

Answer 35

strategies to maintain rivers original flood plain = allowing rivers to flood and intentionally allowing areas of floodplain to build up - this slows down the river flow reaching areas of economic importance + planting trees advantages - slow waters down - recover a rivers natural sedimentation process - helps the soil more efficient at storing water disadvantage - may require a change in land use - eg. a change in farmland

Question 36

advantages and disadvantages of river restoration

Answer 36

restoring a river to its natural course of meanders to slow rivers down + remove impermeable surfaces and replace with natural materials to promote infiltration advantages - more attractive for recreation - create natural habitats which benefit wildlife disadvantages - changes in land use