rivers

Question 1

type of erosion

Answer 1

attrition / abrasion / hydraulic action / solution

Question 2

define river discharge

Answer 2

the volume of water passing a point in the river in a set time

Question 3

types of sediment transportation

Answer 3

saltation / solution / traction / suspension

Question 4

one benefit of building levees to control river flooding

Answer 4

• cheap to construct so allows large areas to be constructed
• natural appearance limits impact on tourism

Question 5

one disadvantage of levees

Answer 5

increases risk of flooding downstream
loss of valuable farmland
less effective than hard construction techniques

Question 6

explain why washlands reduce the risk of flooding somewhere else

Answer 6

excess water floods the washland

therefore rivers discharge is reduced

Question 7

describe how a meander develops into a lake

Answer 7

meander becomes more pronouns allowing narrow neck to form
rover erodes through neck
water takes the fastest route and by passes the old loop
causes deposition build up at entrances of old channel forming an oxbow lake

Question 8

explain one way in which rivers transport their load

Answer 8

solution - rock minerals enter water having been chemically dissolved
suspension - when rock particles are small enough to be carried
traction - when rock material is rolled along a river bed in times of high discharge
saltation - when material is partially in suspension and partially bedlam thus ‘jumping’

Question 9

explain two differences between upper course and lower course river landscapes

Answer 9

• upper course have narrower valleys because discharge is lower - thus less erosion
• lower courses have more meandering because of higher discharge - more lateral erosion
• upper course is irregular and include waterfalls because of lower discharge - less erosion and landscape modification

Question 10

explain one reason why high discharge can increase erosion

Answer 10

• increased velocity so more abrasion

- increased load - increases abrasion

Question 11

explain two ways in which human activities can affect hydrographs

Answer 11

more urbanisation - increases rate of surface run off because more impermeable surfaces - affect lag time - increases discharge

deforestation - affects interception rates - changing run off and lag times

Question 12

for a named river explain why it floods

Answer 12

river seven - antecedent conditions / heavy rainfall - leading to flooding as baneful discharge exceeded

Question 13

describe how river discharge is calculated

Answer 13

width and depth measured to Gove cross sectional area

cross sectional area multiplied by velocity

to give cumbers - cubic metres per second

Question 14

explain how a meander is formed

Answer 14

abrasion takes place on outside of bend - because fastest flowing part of channel - slowest - flowing water on inside bend - so deposition occurs there

Question 15

explain one reason why the antecedent conditions in a drainage basin can affect the peak discharge of a rivers hydrograph

Answer 15

heavy rainfall - ground saturated - can’t take up more water - higher surface run off - smaller lag time and higher peak discharge

Question 16

explain now way that deposition leads to formation of levees

Answer 16

• levees formed when a river is in flood and bursts its banks- load is deposited along the river bank as the river slows down - layers build up

Question 17

explain one reason why river velocity increases downstream

Answer 17

channel becomes wider and deeper downstream - reduces the rampant of friction

Question 18

explain one way channelisation helps manage river landscapes

Answer 18

making channel wider and deeper - increases capacity to hold river water

Question 19

explain one way that weather and climate can affect river erosion

Answer 19

global climate change - increases amount of evaporation - reduces erosion

intense periods of rainfall - increase erosion

Question 20

explain how human actions have increased flood risk

Answer 20

river severn - Tewkesbury

• lots of bridging point settlements increasing vulnerability = urbanisation
• damage - 140,000 of damage for local council + 48000 houses damaged

Question 21

examples of hard engineering strategies

Answer 21

embankments - banks raised to increase channel size
flood walls - increase capacity
flood barriers - stop water flow
channelisation - river channel deepened and widened
dams - built to regulate and control river flow

Question 22

examples of soft engineering strategies

Answer 22

• washland - parts of the floodplain where flooding is allowed
• afforestation - planting trees so more infiltration and less surface run off
• flood warning system
• lands zoning

Question 23

explain formation of a flood plain

Answer 23

form due to both erosion and deposition
erosion removes interlocking spurs creating a wide flat area on either side of river
during a flood material being carried is deposited - as river loses energy
overtime height of floodplain increases as layers of deposition build up

Question 24

explain how a waterfall will change in the future

Answer 24

will retreat - soft rock is easily eroded - by abrasion