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A Level Human Geography > Urban Drainage > Flashcards

Urban Drainage Flashcards

1
Q

Give examples of natural landscapes

A

Forests
Wetlands
Grasslands

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2
Q

What do natural landscapes allow water from rainfall to do?

A

Trap precipitation -> interception

Allow infiltration into the ground

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3
Q

Give examples of impermeable surfaces in urban areas

A

Roads
Car parks
Rooftops
Pavements

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4
Q

How are urban areas designed to cope with large amounts of precipitation?

A

Underground pipes
Sloping roofs
Guttering
Cambered roads

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5
Q

What characteristics of urban areas contribute to large amounts of surface runoff?

A

Impermeable surfaces -> prevent infiltration

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6
Q

How does reduced infiltration in urban areas affect the hydrological cycle?

A

Up to 20% less groundwater
Lower soil moisture levels
-> Lower base level flows of an urban river than pre-urban river
Up to 30% more surface runoff

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7
Q

Why are urban areas more likely to suffer from floods after heavy rainfall than rural areas?

A

Urban drainage systems release rainwater into rivers / streams
-> flooding

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8
Q

Give some case study information about urban flood risk

A

The Asian Development Bank (ADB) -> Asian population vulnerable to inland flooding predicted 350 million by 2050.

The Red Cross -> almost half of the natural disasters they dealt with in 2014 were caused by floods

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9
Q

Give the issues associated with urban river catchment management

A

Pollution =
• road salt
• sediment from building sites / riverbank erosion
• oil, grease, chemicals from cars
• heavy metals from car exhausts
• pesticides / nutrients from parks, gardens

River flow =
• increased flow -> flooding + erosion during wet periods
• decreased flow -> harms fish + aquatic wildlife during dry weather

  • > higher water temps disturb ecosystems
  • > large amount of water in sewage treatment -> raw sewage in water system
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10
Q

What is a hydrograph?

A

A graph showing the rate of flow (discharge) compared to time past a specific point in a river, or other flow

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11
Q

What are the rate of flow and precipitation measured in on a hydrograph?

A

Rate of flow = Cubic metres per second

Precipitation = millimetres

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11
Q

What is meant by ‘peak rainfall’ on a hydrograph?

A

The time of highest rainfall

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12
Q

What is meant by ‘peak discharge’ on a hydrograph?

A

The time when the river / channel reaches its highest flow.

-> later than peak rainfall because of lag time

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13
Q

What is meant by ‘lag time’ on a hydrograph?

A

The time between peak rainfall and peak discharge

-> time taken for water to find its way to the river / channel

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13
Q

What does the ‘rising limb’ on a hydrograph show?

A

Shows that the normal / base flow of the river is increasing.
-> when runoff, ground water, soil water reach the river / channel

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14
Q

What does the ‘falling limb’ on a hydrograph show?

A

Shows that water is still reaching the river / channel, but in decreasing amounts

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15
Q

What does SUDS stand for?

A

Sustainable urban drainage system

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16
Q

What is the purpose of SUDS?

A

Provides a natural approach to managing urban drainage -> prevent flooding + water pollution

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17
Q

How does SUDS work?

A

SUDS works by slowing down the surface run off from a site -> allows natural processes to break down pollutants

19
Q

Give advantages of SUDS

A

Allows natural processes (e.g. Infiltration) to break down pollutants in water.
Relieves pressure on traditional drainage systems.

20
Q

What does Source Control SUDS do?

A

Deal with surface runoff close to where the rainfall lands.

21
Q

Name the different types of SUDS

A

Source control SUDS
Site control SUDS
Regional control SUDS

22
Q

What does Site Control SUDS do?

A

Manage surface runoff from larger areas eg major roads.

23
Q

Where are Regional Control SUDS often found / what does it do?

A

Downstream from Source and Site Controls.

Deal with the runoff from large areas.

24
Q

How do different SUDS work together?

A

Rainwater that passes through smaller SUDS can then feed into the larger SUDS.
It is best to have the water run through swales, filter drains, or ditches rather than pipes.

26
Q

Name examples of SUDS

A 
Swales
Permeable paving (source Control)
27
Q

What are Swales?

A

Swales are shallow, broad and vegetated channels designed to store and/or convey runoff and remove pollutants.
They may be used as conveyance structures to pass the runoff to the next stage of the treatment train.
Can be designed to promote infiltration where soil and groundwater conditions allow.

28
Q

Give advantages of swales

A
  • Easy to incorporate into landscaping.
  • Good removal of urban pollutants.
  • Reduces runoff rates and volumes.
  • Low capital cost.
  • Maintenance can be incorporated into general landscape management.
  • Pollution and blockages are visible and easily dealt with.
29
Q

Give disadvantages of swales

A
  • Not suitable for steep areas or areas with roadside parking.
  • Limits opportunities to use trees for landscaping.
  • Risks of blockages in connecting pipe work.
30
Q

What is permeable paving?

A

Surfaces suitable for pedestrian / vehicles -> allowing rainwater to infiltrate into underlying layers.
Surfaces with an aggregate sub-base can provide good water quality treatment.

31
Q

What can permeable paving allow rainwater to do before infiltrating?

A

The water can be temporarily stored, reused, or discharged to a watercourse or other drainage system.

32
Q

Give advantages of permeable paving

A
  • Reduced peak flows to watercourses reducing the risk of flooding downstream.
  • Reduced effects of pollution in runoff on the environment.
  • Reduced need for deep excavations for drainage -> significant cost benefits.
  • Lined systems can be used where infiltration is not desirable, or where soil integrity would be compromised.
  • Allows dual use of space, so no additional land take.
  • Removes need for gully pots and manholes.
  • Eliminates surface puddles and surface ice.
  • Not much maintenance required.
  • Good community acceptability.
33
Q

Give disadvantages of permeable paving

A
  • Cannot be used where large sediment loads may be washed/carried onto the surface.
  • In the UK, current practice is to use on highways with low traffic volumes, low axle loads and speeds of less than 30 mph.
  • Risk of long-term clogging and weed growth if poorly maintained.
34
Q

What is a catchment?

A

A catchment is something that is for collecting water.

Eg reservoir, natural basin.

35
Q

What can the movement of water be displayed by?

A

Hydrographs

36
Q

What are storm drains?

A

Drainage systems that run directly into rivers

37
Q

Define drainage basin

A

An enclosed area to which run off drains by gravity into a river, lake or other body of water.

38
Q

Give types of water storage

A

Drainage basin
Vegetation - interception
Surface storage - pond, lake, puddle
Ground water storage - water table

39
Q

What has caused a loss of natural drainage basin stores?

A

Development of urban areas

40
Q

Name the place that is the case study for urban drainage

A

Cheonggyecheon river project

-> Seoul, South Korea

41
Q

What is the population of Seoul

A

24 million = megacity

42
Q

Where is Cheonggyecheon located in Seoul and what was it built on?

A

Cheonggyecheon

  • > a central area of the city.
  • > built over the course of a small seasonal stream.
  • > 1958-1961 the stream was fully covered over, major road built on top.
43
Q

What was done to restore the river that was covered over in Cheonggyecheon?

A

2003
$281 million scheme
Restore the river -> transform it into a 5.8km ecologically sensitive green pedestrian corridor

44
Q

What was the reason for the project to restore the river in Seoul?

A

South Korea is putting more emphasis on health, sustainability and social responsibility.

45
Q

Give examples of the work that was carried out in order to restore the river in Seoul

A

• 22 bridges were built - 12 pedestrian, 10 for cars.
-> improve connectivity between the city’s north and south.
• Water is pumped to the area from nearby Hanang River.
-> create constant flow.
• Water is treated to remove pollution.

46
Q

What issue would’ve been caused by the restoration of the river? What did authorities do to address this issue?

A

Concerns that traffic would be disrupted -> businesses would suffer.
Seoul Metropolitan authority…
-> extra parking with lower fees.
-> improved loading / unloading systems.
-> promoted business in Cheonggyecheon.
-> provided businesses with restructuring grants.

47
Q

What positives came out of the river restoration project in Cheonggyecheon?

A
  • Hasn’t affected traffic as much as expected.
  • Higher house prices -> more investment / restoration.
  • Temperature reduction of 2.5°C -> due to road being removed.
  • Re-established former habitat of the stream -> ‘urban wildlife haven’.

A Level Human Geography (15 decks)

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