Urban Drainage

Question 1

What is a drainage basin

Answer 1

The area of a land drained by a river and its tributaries

Question 2

What is a watershed

Answer 2

The boundary dividing the drainage basin from another

Question 3

What is precipitation

Answer 3

Rain snow

Question 4

What is interception

Answer 4

Things stopping precipitation from reaching the ground

Question 5

What is transpiration

Answer 5

Evaporation from leaves

Question 6

What is evaporation

Answer 6

Water turning to gas

Question 7

What is surface storage

Answer 7

Eg puddles

Question 8

What is infiltration

Answer 8

Water being absorbed into the soil

Question 9

What is surface run off and overland flow

Answer 9

Water running on surface of ground- to river or drains

Happens in impermeable areas
Happens at slope

Question 10

What is soil moisture

Answer 10

Water in soil

Question 11

What is percolation

Answer 11

Water being absorbed into rocks

Question 12

What is groundwater

Answer 12

Water in the ground

Question 13

What is ground water flow

Answer 13

Water flowing through the ground

Question 14

What is throughflow

Answer 14

Water flowing through soil

Question 15

Eg of input

Answer 15

Precipitation

Question 16

Eg of storage

Answer 16

Interception

Surface storage

Soil moisture

Groundwater

Question 17

What are flows

Answer 17

Ground water flow

Through flow

Percolation

Infiltration

Surface run off and overland flow

Question 18

Eg of output

Answer 18

Evaporation

Transpiration

River channel

Question 19

Hydrological cycle in urban environment

Answer 19

Evaporation

to precipitation

to surface storage (back to evaporation or)

run off

Question 20

Hydrological cycle in rural environments

Answer 20

Evapotranspiration to precipitation

to interception by vegetation (can be evaporated)

to surface storage (can be evaporated)

to surface run off AND soil water storage

to ground water storage

Question 21

Storm hydrograph

Basin lag time

Answer 21

Time between the highest rainfall and highest discharge in hours —

Happens as only 9% of water lands in the river and the other % has to make its way through flows etc

Question 22

What is the line with the rising and recession limb

Storm hydrograph

Answer 22

Line shows discharge in metres squared per second

Question 23

What is base flow

Storm hydrograph

Answer 23

The usual flow of the river

Question 24

What is recovery rate

Storm hydrograph

Answer 24

Where through flow an the main line meet

Question 25

What are sustainable drainage systems

Answer 25

Hold back and slow surface run off in urban areas and allow natural processes to break down pollutants

Question 26

Name the 7 sustainable urban drainage systems

Answer 26

Swales

Permeable roads

Bio retention basins

Detention basins

Rain gardens

Green roofs

Water butts

Question 27

How do Swales work

Answer 27

Wide shallow channels which store excess water

Question 28

How do permeable roads and pavements work

Answer 28

Absorb rain water

Question 29

How do bio retention basins work

Answer 29

Contain gravel or sand layers beneath reed beds

The basins collect and filter water as well as providing habitats

Question 30

How do detention basins work

Answer 30

Like bio retention basins but are designed only to store water and prevent flooding

They are usually dry

Question 31

How do green roofs work

Answer 31

Planted with wild flowers and absorb rainwater to reduce run off

Question 32

How do water butts work

Answer 32

Connected to down pipes and collects rain water from house roofs

Question 33

What are some of the benefits of suds

Answer 33

Slows down surface run off allowing infiltration- reducing risk of flood and sewer and drain overflow

Polluted water an be filtered as infiltrated in ground

More infiltration means more groundwater and potentially less drought

Wildlife habitats are improved

Green space improve the physical feel and emphasise the aesthetic appeal of new developments

Question 34

6 urban flood management strategies

Answer 34

Land use zoning

Dredging

Flood walls

Flood warning

Straightening the channel and channelisation

River restoration

Question 35

Explain land use zoning

Answer 35

Restrict the construction of buildings and other impermeable surfaces on the flood plain

Can provide sport and recreational opportunities but restricts short term economic potential

Can’t undo what’s done

Question 36

Explain dredging

Answer 36

Deepen the river channel and increase its capacity

Material removed from river bed can be used to build up river banks
But ugly and will need to be repeated

Question 37

Explain flood walls

Answer 37

Construct hugger river banks and increase the channels capacity

Higher river banks walls will allow greater discharge

Reduced flood risk but ugly and expensive to do and maintain

Question 38

Explain flood warnings

Answer 38

Prepare people so lives can be saved

Doesn’t always work

Property destroyed

Question 39

Explain Chanel straightening and channelisation

Answer 39

Remove meanders and increase the velocity of river flow

The Increased velocity means that the river will travel at a faster rate but floods made be displaced downstream to the point where the river slows/meanders

Question 40

Explain river restoration

Answer 40

Returning the river to a more natural state by restoring habitats, recreating meanders and removing obstructions to create a more natural system

Wildlife habitat is restored but local residents may oppose to the plan as they don’t understand how it can reduce flooding- BUT EDUCATE THEM?