rivers- floods and hydrographs

Question 1

give flood relief channel example

Answer 1

Jubilee River – River Thames​
Constructed to reduce flood risk in a number of towns, 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 2

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

Answer 2

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 3

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

Answer 3

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 4

environmental issues of flood relief channels in jubilee river

Answer 4

Extensive flooding in 2014 below the confluence of the River Thames and the flood relief channel damaged habitats​

Concrete weirs are unattractive.​

Question 5

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

Answer 5

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 6

What are the 3 levels of flood warnings?

Answer 6

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

Question 7

• define and describe the human factors of flooding

Answer 7

Urbanisation- impermeable surfaces mean water flows quickly into drains, sewers and river channels

deforestation- when trees are removed, much of the water which had been evaporated from leaves or stored on leaves and branches flows rapidly into river channels

agriculture- exposed soil can lead to increased surface runoff

Question 8

• what causes flooding

Answer 8

river floods usually occur after long periods of rain- most frequently during winter

sudden floods, called flash floods, tend to occur in summer and associated with heavy rainstorms

]physical and human factrs can increase flood risk

Question 9

physical causes of flooding

Answer 9

Long periods of rain causes soil to become saturated leading to runoff.

Steep-sided valleys channel water to flow quickly into rivers causing greater discharge.

Impermeable rocks cause surface runoff to increase river discharge.

Question 10

What is a hydrograph?

Answer 10

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

Question 11

what is a flashy hydrograph

Answer 11

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

rapid response hydrograph posing a high flood risk

Question 12

What is a ‘flat’ hydrograph?

Answer 12

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

Question 13

describe physical/human causes of flooding affecting a hydrograph

Answer 13

steep slopes resulting rapid runoff

impermeable rocks encouraging rapid overland flow

heavy or prolonged rainfall

saturated or frozen soils

deforestation encourages rapid transfer of water to rivers

urbanization- impermeable surfaces encourage rapid overland flow

Question 14

physical/human causes of flooding resulting in flat hydrograph

Answer 14

gentle slopes slow down water transfer

permeable rocks allowing water to soak into rocks where transfer is slow

drizzle

deep dry soils able to absorb water

afforestation resulting in water being intercepted and evaporated