Geography CUE: 3.2.3.5

Question 1

Condensation (hygroscopic) nuclei

Answer 1

PM (particulate matter) that provides a surface for water vapour to condense onto. Because there is more pollution in urban areas = more condensation nuclei = greater cloud formulation = more rain

Question 2

Greater convection

Answer 2

Convection is rising of air. Urban areas are hotter due to the UHI (Urban Heat Island) = hot air is less dense so it rises and then cools. As the air cools - more condensation = more clouds

Question 3

What happens to water in urban areas

Answer 3

• Buildings designed to shed water sloping roof –> drains –> sewage
• More surface runoff as ground is impermeable
• More Condensation (due to Condensation nuclei / air pollution)
• Less interception as there is less vegetation / trees

Question 4

Infiltration definition

Answer 4

The process by which water soaks into, or is absorbed by, the soil.

Question 5

Surface run-off definition

Answer 5

Surface runoff (also known as overland flow) is the flow of water that occurs when excess stormwater, meltwater, or other sources flows over the earth’s surface.

Question 6

Discharge definition

Answer 6

River discharge is the volume of water flowing through a river channel.

Question 7

Through flow definition

Answer 7

Water flows downhill within the soil.

Question 8

Groundwater flow definition

Answer 8

The deeper movement of water through underlying permeable rock strata below the water table.

Question 9

Interception definition

Answer 9

This is when precipitation lands on buildings, vegetation and concrete before it reaches the soil.

Question 10

Storm Hydrographs - between urban and rural

PRECIPITATION

Answer 10

They are the same

Question 11

Storm Hydrographs - between urban and rural

RISING LIMB

Answer 11

Urban has a steep rising limb where as rural has a gentle rising limb. Quicker in urban, slower in rural.

Question 12

Storm Hydrographs - between urban and rural

PEAK DISCHARGE

Answer 12

A lot higher in urban than rural more likely to flood

Question 13

Storm Hydrographs - between urban and rural

LAG TIME

Answer 13

A lot longer in rural than urban

Question 14

Storm Hydrographs - between urban and rural

OVERALL WATER RECORDED IN THE RIVER

Answer 14

A lot higher in urban area below blue line

Question 15

Precipitation in urban areas

Answer 15

Urban areas have traditionally been designed and built to shed water and remove it as quickly as possible. This is though impermeable surfaces which produce high levels of surface run-off with very little infiltration. Gutters, drains and sewers etc then transfer the water to rivers and water courses very quickly. Thought this results in rivers which respond very quickly to storm (precipitation) events, with short lag-times and high peak discharge. These are known as ‘flashy’ Hydrographs. Combined with the fact that rivers in urban areas are often highly controlled and their courses restricted means flooding is common in urban areas.

Question 16

What are the issues associated with managing water in urban areas?

Answer 16

River flow:
- Increased flow leads to flooding and erosion of the river bank during wet periods
- Decreased flow during dry weather harms fish and other aquatic wildlife

Issues:
- Higher water temperatures can disturb ecosystems
- Very high flows can overload the foul water system resulting in raw sewage on the surface

Pollution:
- Sediment from building sites, river bank erosion
- Oil, grease and toxic chemical from cars
- Heavy metals from car exhausts
- Pesticides and nutrients from parks and gardens
- Viruses from pet waste
- Road salt

Question 17

Which of these issues do you think poses the greater challenge in urban areas?

Answer 17

• Pollution from industry and buildings as it is most prevalent in cities and uses harmful chemical ect
• Cities with monsoon or heavy rainfall periods and seasons would have a worse impact from pesticides and nutrients as it will be washed away quicker.
• LIC have lower hygiene levels so more likely to be effected by waste.

Question 18

What are Sustainable Urban Drainage Systems?

Answer 18

They manage water in urban areas to reduce flooding & risk, whilst also improving water quality, biodiversity and providing amenity for the local community. They normally try and mimic the ‘natural’ process that occurs within the water cycle.

Question 19

Why are they needed?

Answer 19

Urban areas have uncharacteristically high levels of impermeable surfaces, which in turn increases surface run-off, reducing the lag-time and therefore results in more frequent flooding. Pollution builds on roads over time and can be washed into water courses after a period of rainfall.

Question 20

Example of SUDS

SWALES

Answer 20

Description of type:
- Shallow vegetated channel that often runs alongside a road or impermeable surface

Benefits:
- Can hold / temporarily store water during periods of heavy rainfall. Allows water to infiltrate over time. Bothe reduce flood risk.
- Vegetation can filter out larger materials whilst other pollutants can be absorbed by the vegetation or broken down through organic processes.
- Vegetation can provide habitats for insects and other wildlife, increasing biodiversity.

Question 21

Example of SUDS

GREEN ROOFS

Answer 21

Description of type:
- Roof covered in vegetation or another medium. THe effectiveness of a green or living roof will depend on the thickness of the substrate on the roof, provides attenuation and other benefits such as biodiversity enhancement and thermal cooling.

Benefits:
- Has insulating properties and increases evapotranspiration (EVT)
- Improve the drainage system sustainably
- Supporting wildlife habitats
- Boosting thermal performance

Question 22

Examples of SUDS

PERMEABLE TARMAC / SURFACE

Answer 22

Description of type:
- Allows water to soak into the ground or a gravel-filled base. Permeable surfaces can attenuate the flow and provide treatment. Good for constrained sites as provides drainage + car parking function.

Benefits:
- Reduce build up of surface runoff and flooding. Helps to reduce water pollution.
- Filtering rainwater through the pavement helps remove pollutant
- Heat Island Effect Mitigation - permeable pavements can lower surface temperatures

Question 23

Example of SUDS

DETENTION BASINS (temporary) Retention ponds (permanent)

Answer 23

Description of type:
- Excavated basins for temporary storage of water during flood events

Benefits:
- Allows for infiltration and ground-water recharge
- Easy to maintain
- Simple to design and construct
- Potential for dual land use
- Protect ecosystem and Human settlements

Question 24

Example of SUDS

WATER BUTTS (rainwater harvesting)

Answer 24

Description of type:
- Precipitation is collected from roofs and stored in water butts for repurposing in toilets and watering gardens

Benefits:
- Eco-friendly
- Relatively cheap and easy to implement and maintain
- Provides self-sufficiency for households
- Surplus water in the North of England could be used to supply

Question 25

Example of SUDS FILTER STRIPS

Answer 25

Description of type: - Gently sloping, veitated strips of land that provide opportunities for slow conveyance and infiltration Benefits: - Effective at removing polluting solids through filtration and sedimentation - Encourages evaporation and can promote infiltration - Easily integrated into landscaping and can be designed to provide aesthetic benefits.

Question 26

Lamb Drove, Residential SuDS scheme, Cambourne Cost compared to traditional schemes

Answer 26

The estimated cost savings due to SuDS is approximately £11k (around 10%). In addition, each house will have two water butts to collect rainfall from the roof, which can be used for watering gardens and other applications for which rainwater is sustainable. Omission of the new storm sewer connection should give some financial benefits (approximately £30 / year / household) to the residents as it avoids the annual payment of storm water disposal changes to the sewage undertaker.

Question 27

Lamb Drove, Residential SuDS scheme, Cambourne Protection against flooding

Answer 27

- Water butters - Permeable paving - A green roof - Swales - Filter strips - Detention and wetland basins - A retention pond

Question 28

Lamb Drove, Residential SuDS scheme, Cambourne Consideration of climate change

Answer 28

In the early stages of the design, it was found that the full attenuation of runoff to a 1:100 year standard, with allowance for climate change, could be accommodated within the site boundary.

Question 29

Lamb Drove, Residential SuDS scheme, Cambourne Impact on water flow

Answer 29

The Lamb Drove Site has attenuated surface water flows, significantly reduced peak flows have been observed when compared to the control site.

Question 30

Lamb Drove, Residential SuDS scheme, Cambourne Impact on water quality

Answer 30

SuDS has improved the quality of water discharged from Lamb Drove when compared to the control site. Results have shown that Lamb Drove has observed reductions in concentration of a variety of pollutants and other water quality indicators.

Question 31

Lamb Drove, Residential SuDS scheme, Cambourne Biodiversity

Answer 31

Substantial improvement in the biodiversity, ecology and subsequent quality of life at Lamb Drove compared to typical residential developments.

Question 32

Lamb Drove, Residential SuDS scheme, Cambourne Amenity

Answer 32

Larger SuDS components also contribute to provision of green space, green infrastructure, visual amenity and promoting wildlife.

Question 33

Lamb Drove, Residential SuDS scheme, Cambourne Any issues created

Answer 33

- Need to keep SuDS simple, as this will reduce maintenance costs and the likelihood of system being well maintained into the future. Also a key advantage of Swales and other surface - based SuDS is that problems can be observed and dealt with as they arise. - In high density developments, SuDS are likely to rely more heavily on special treatments of hard areas (such as Permeable paving or green roofs) with potentially higher costs and differ maintenance requirements. - SuDS can be incorporated into any terrain as they do not necessarily depend up infiltration into into porous sub-strata. SuDS can equally well be incorporated into the surface landscaping of impervious ground such as clay similar to Lamb Drove.

Question 34

River Restoration Scheme - Cheonggyecheon River, Seoul Background information

Answer 34

Mega City - 26 million people 27.8% green areas - MAintained the water flow depth and quality of 40cm by pumping from the River Hanang - Population density of 17,000 people per km^2

Question 35

River Restoration Scheme - Cheonggyecheon River, Seoul Reasons for and aims of the project

Answer 35

- An ecologically sensitive pedestrian corridor which improves the environment - To dismantle the elevated freeway and concrete deck above the stream - Improve the quality of life of people in Seoul - To remove the safety risks posed by the decaying freeway built over the top of the river - To increase business competitiveness and connectivity either side of the river (North and South)

Question 36

River Restoration Scheme - Cheonggyecheon River, Seoul What work was carried out / what did they do?

Answer 36

1. Car use was discouraged during the scheme and rapid bus lanes were added 2. 22 Bridges added in total including 12 pedestrian bridges and 10 motorist bridges to improve communications from North to South across river 3. The Hanang River was used as source of water pumped into the Cheonggyecheon River to deal with variable flow rates and maintain a regular flow of 40cm depth. The pumped in water is treated to prevent pollution 4. The historic Central zone had underground waterways redirected and given a new stream bed and landscaped banks.

Question 37

River Restoration Scheme - Cheonggyecheon River, Seoul Attitudes and contributions of parties involved

Answer 37

- South Korean president Lee Myung Bak included to restoration of the stream in his successful bid to become the Mayor of Seoul in 2001, and it become a priority for his administration - Transportation experts were concerned that removing the elevated high would increase traffic congestion and chaos in the northern end of the city since it arrived 169,000 vehicles per day.

Question 38

River Restoration Scheme - Cheonggyecheon River, Seoul Evaluation - Successes

Answer 38

- Festivals where held there and restored culture - Manage flood risk - Increased tourism --> more money + work - Reduce pollution and congestion - Reduction in Urban Heat Island - Increase wind speed by 50%

Question 39

River Restoration Scheme - Cheonggyecheon River, Seoul Evaluation - Failures / Challenges

Answer 39

- Cheonggyecheon was partially dry by the time the expressway was demolished subsequently making Cheonggyecheon an urban development as the steam does not flow naturally. Due to these factors, minimal sustainability has been achieved.

Question 40

River Restoration Scheme - Cheonggyecheon River, Seoul Overall judgement - consider economic, environmental and social impacts

Answer 40

Economic sustainability: Despite it's Central location the area had fallen behind the rest to Seoul in terms of economic viability. Since the end of the project, development capital has been invested in residential construction and property prices have risen are double the rates elsewhere in the city. The number of businesses in the areas closets to the restoration work has risen, compared with decreasing trends in most other city District. The stream has re-established lost habitats, plant and animal. Species have reappeared, and it has become an urban wildlife haven.