River Landscapes and Processes

Question 1

what is a water shed

Answer 1

boundary of a drainage basin separates one drainage basin from another and is usually high land, such as hill s and ridges

Question 2

what is a tributary

Answer 2

a stream or small river that joins a larger stream or river

Question 3

what is a source

Answer 3

the starting point of a stream or river, often a spring or a lake

Question 4

what is a confluence

Answer 4

a point where two streams or rivers meet

Question 5

what is a mouth

Answer 5

the point where a river leaves its drainage basin and flows into sea

Question 6

types of weathering

Answer 6

mechanical
chemical
biological

Question 7

mass movement that affects river valleys

Answer 7

soil creep
sliding
flows

Question 8

erosion processes that effect river valleys

Answer 8

hydraulic action
abrasion
solution
attrition

Question 9

what is hydraulic action

Answer 9

sheer force of water hitting the river bed and banks and wearing them away

Question 10

what is abrasion

Answer 10

material carried in river rubbing against bed and banks of the channel and wearing them away

Question 11

when does deposition occur

Answer 11

when a river no longer has enough energy to carry its load

Question 12

what happens as rivers discharge and velocity reduce

Answer 12

heaviest material is deposited first

Question 13

4 types of transportation

Answer 13

traction
saltation
suspension
solution

Question 14

what does size of waves depend on

Answer 14

fetch - distance over sea the wave has travelled over
how long wave travelled for
strength of wind
time of wind blowing

Question 15

physical causes of flooding

Answer 15

intense rainfall
duration of rainfall
snow melt
relief

Question 16

human causes of flooding

Answer 16

deforestation
urbanisation

Question 17

why flood risk is going to increase

Answer 17

change in land use
increasing population
changes to weather patterns from climate change

Question 18

what does a hydrography show

Answer 18

how a river responds to a storm event

Question 19

what are the key features of a hydrograph

Answer 19

rising limb
lag time
falling limb

Question 20

what is rising limb in a hydrograph

Answer 20

rapid rise in water after a period of heavy rainfall

Question 21

what is lag time in a hydrograph

Answer 21

difference between time of heaviest rainfall and point at which the river contains the largest amount of water

Question 22

what is falling limb in a hydrograph

Answer 22

reduction in amount of rainfall reaching the channel

Question 23

what does environmental agency do

Answer 23

building flood defences

helping people prepare for flooding and giving flood warnings

Question 24

hard engineering techniques

Answer 24

levees
dams and reserovirs
flood relief channels
channelisation

Question 25

disadvantages of levees

Answer 25

burst under pressure causing more damage

Question 26

advantage of levees

Answer 26

stop water from spreading into areas where it could cause problems

Question 27

advantages of channelisation

Answer 27

allows more water to run through the channel more quickly, taking it away form places at risk

Question 28

disadvantage of channelisation

Answer 28

may put other places at risk
does not look natural

Question 29

advantages of flood relief channels

Answer 29

accommodate high flows so that a river wont over flow its banks

Question 30

disadvantages of flood relief channels

Answer 30

high costs
unsightly

Question 31

soft engineering techniques

Answer 31

washlands
river restoration
flood plain zoning

Question 32

advantages of washlands

Answer 32

safe place for floodwater to go
help slow flood water down

Question 33

disadvantages of washlands

Answer 33

allowing land to flood may limit the use of the land fo recreation

Question 34

advantages of river restoration

Answer 34

more attractive and create natural habitats

Question 35

advantages of flood plain zoning

Answer 35

prevents building homes and businesses in high risk zones

Question 36

how land is used to decrease flooding

Answer 36

afforestation
managing drainage
managing farmland

Question 37

formation of waterfalls and gorges

Answer 37

waterfall is formed along a river when a band of hard, more resistant rock lies over a band of soft, less resistant rock

1. river erodes the less resistant rock at a faster rate, gradually undercutting the more resistant rock. The continued erosion of the soft rock by abrasion and hydraulic action causes an overhang of hard rock
2. eventually hard rock cant support its own weight and collapses under force of gravity. Force of falling water and abrasion by boulders leads to erosion of river bed and the formation of a plunge pool
3. as soft rock continues to be eroded and the hard rock collapses, a steep sided gorge is formed as the waterfall retreats upstream
4. gorges form in hard rocks where vertical erosion by rivers is dominant

Question 38

formation of interlocking spurs

Answer 38

in upper course, discharge is low. River uses most of its energy overcoming friction with the channel. What energy it has left over is used by hydraulic action to deepen the channel by vertical erosion

resistant rock is in the upper course. Freeze thaw weathering gradually widens the river channel, giving the valley a steep v shaped cross profile. Over time this weakens rock which breaks loose and shifts down valley sides. This is then transported by river more downstream

winding path taken by the river is due to obstacles of hard rock in its path. The river takes the easiest route over land. This results in interlocking spurs

Question 39

formation of flood plains and levees

Answer 39

floodplains and levees can be found in lower course. Floodplains are flat, wide areas of land either side of the river

river transports sediment downstream. When river floods it transports sediment over floodplain. When flood occurs river loses energy depositing largest sediment almost immediately in sides of river banks. Whereas small sediment is carried further onto the floodplain

if flooding continuously occurs, the deposited sediment increases raising height of levees and flood plains

this also increases river channel, which can then cope with a higher discharge and flooding is less likely to occur in the future

Question 40

meanders and oxbow lakes

Answer 40

a meander is a slight bend in river. As water flows through meander it travels faster on outside bend creating erosion . This undercuts riverbank forming river cliff. Whereas water travels slower on inside bend causing deposition to create slip off slope

as bend becomes more extreme, the rivers current will begin to erode the neck of the meander know as lateral erosion

the meander neck continues to be eroded becoming smaller and narrower over time

continued erosion causes river to cut through the neck of meander completely making a shortcut for river current. Material will then be deposited t the side of the river bank where former river channel travels through

now the channel becomes more established, due to deposition so previous channel begins to dry up

over time the former meander becomes completely separated from the river channel and no longer receives river water

marsh plants colonise the area which widens the gap further. This is know as an oxbow lake

Question 41

what to do in the event of a flood

Answer 41

gather essentials together upstairs
fill jugs and saucepans with clean water
move family and pets upstairs
turn off gas, electricity and water supplies
keep listening to local radio
avoid walking through and touching the water