rivers 2

Question 1

What is a hydrograph?

Answer 1

A graph showing how a river responds to a storm, showing the rainfall and discharge over time

Question 2

What is a ‘flashy’ hydrograph?

Answer 2

A hydrograph with a short lag time and a high peak discharge

Question 3

What is a ‘flat’ hydrograph?

Answer 3

A hydrograph with a long lag time and a low peak discharge

Question 4

Which factors influence the shape of a flood hydrograph?

Answer 4

Basin size
Drainage density
Rock type
Land use
Relief
Rainfall intensity

Question 5

What is ‘lag time’?

Answer 5

The time between peak rainfall and peak discharge on a hydrograph

Question 6

What is antecedent rainfall?

Answer 6

The amount of rain that has already fallen prior to a specific event

Question 7

Define ‘interception’

Answer 7

Leaves and tree branches catch rainfall and prevent it from running into the river

Question 8

Define ‘infiltration’

Answer 8

Rain that soaks into the top layers of the soil and rock below

Question 9

What is impermeable rock?

Answer 9

Rock which water is not able to flow through

Question 10

What is permeable rock?

Answer 10

Rock which water is able to flow through

Question 11

Name a range of hard engineering stategies used to manage river flooding?

Answer 11

Reservoirs and dams
Channel straightening
Embankments
Flood relief channels

Question 12

Name a range of soft engineering strategies used to manage river flooding?

Answer 12

Afforestation
Land use zoning
River restoration
Wetland restoration
Flood warnings

Question 13

How do dams regulate water flow?

Answer 13

Durings periods of high rainfall, water is stored in the dam.

Water is released when rainfall is low

Question 14

Why is building dams controversial?

Answer 14

They are very expensive
Land is flooded to create the reservoir
People are relocated to make way for the dam

Question 15

What are the benefits of dams?

Answer 15

They are multi purpose - so they can be used to generate HEP as well as manage river flow.
They are affective holding back water in times of potential flood
They are long lasting

Question 16

Most dam schemes are multi-purpose. What are their main functions?

Answer 16

Flood prevention
Irrigation
Water supply
Hydro-electric power generation
Recreation e.g. sailing

Question 17

What is channel straightening?

Answer 17

Cutting through meanders to create a straight channel to speed up water flow

Question 18

What are the advantages of channel straightening?

Answer 18

It moves water out of an area quickly as water passes through a straight channel quicker than a meandering channel.

Question 19

Why is channel straightening problematic?

Answer 19

It may increase the risk of flooding further downstream

Question 20

What are river embankments?

Answer 20

Raised riverbanks which allow the river channel to hold more water and prevent flooding

Question 21

What are the advantages of river embankments?

Answer 21

Embankments increase the volume of water that the river can hold, reducing the risk of flooding.

Question 22

What are the problems with embankments?

Answer 22

Not always effective. Water can rise above the embankments, causing flooding.

Question 23

What are flood relief channels?

Answer 23

A man-made river channel constructed to by-pass an urban area

Question 24

What are the benefits of flood relief channels?

Answer 24

River discharge can be controlled by using gates to control water levels.

Question 25

What are the disadvantages of flood relief channels?

Answer 25

How does floodplain zoning work?

Question 26

How does floodplain zoning work?

Answer 26

It restricts different land uses to certain locations on the floodplain. Expensive/important land uses are placed further away from the river e.g. housing and industry Low-value uses are placed close to the river e.g. pasture and parkland.

Question 27

What are the advantages of flood plain zoning?

Answer 27

Consideration into the landuse around the river is taken which means concrete surfaces are not used, reducing impermeable surfaces close to river. Less damage occurs as important facilities are located futher away.

Question 28

What are the disadvantages of flood plain zoning?

Answer 28

It limits the uses of land closes to a river It is almost impossible to use flood plain zoning on land that has already been built on

Question 29

What is river restoration?

Answer 29

Making the river more natural. For example: When rivers have previously been artificially starightened they are returned to their original course. Removing levees so that the river floods naturally The purpose of this is to prevent flooding further downstream.

Question 30

What are the benefits of river restoration?

Answer 30

Less risk of flooding downstream Limited maintenance needed Creates habitats for birds

Question 31

What are the problems with river restoration?

Answer 31

Flooding can increase | Major floods are more likely unless planning takes place.

Question 32

How does afforestation help manage river flooding?

Answer 32

Planting trees to intercept and absorb water reduces surface run off.

Question 33

Who issues flood warnings in England and Wales?

Answer 33

The Environment Agency

Question 34

What are the 3 levels of flood warnings?

Answer 34

1. Flood Watch 2. Flood Warning 3. Severe Flood Warning

Question 35

What would people be encouraged to do by the Environment Agency to prepare for a flood?

Answer 35

1. Plan what to do eg. move possessions upstairs 2. Use flood gates to prevent water entering their property 3. Use sandbags to keep floodwater away from buildings

Question 36

give flood relief channel example

Answer 36

Jubilee River – River Thames​ Constructed to reduce flood risk in a number of towns, this stretch of the river is highly developed with extensive housing developments and infrastructure​ Completed in 2002, cost £110 million​ New river is 12km in length and up to 50m wide. Maintained in low flow conditions, takes excess water from the River Thames

Question 37

what were the social issues of the flood relief channel in jubilee river

Answer 37

Protection of wealthy properties in Maidenhead and Eton at the expense of less affluent areas further downstream at Wraysbury.​ Paddle boaters promised a fully navigable river are disrupted by weirs

Question 38

what were the economic issues of flood relief channels in jubilee river

Answer 38

it was the most expensive flood relief scheme in the UK. Floods in 2003 damaged weirs – the cost of maintenance is quite high.​ Additional local relief measures are required downstream; the scheme has not so much solved the problem but shifted it elsewhere – serious flooding in 2014.​

Question 39

environmental issues of flood relief channels in jubilee river

Answer 39

Extensive flooding in 2014 below the confluence of the River Thames and the flood relief channel damaged habitats​ Concrete weirs are unattractive.​