Urban precipitation and drainage

Question 1

Impacts on drainage basin storage areas

Answer 1

• drainage systems act as systems of inputs, transfers, outputs and stores
• relationship between variables is dynamic- they will change with circumstances
• urbanisation is significant in altering storage

Question 2

Urban drainage system

Answer 2

Inputs= Precipitation
Outputs= Evapotranspiration/ Runoff
Store= Soil, rock, surface (impermeable) and plants

Question 3

2 challenges of the urban water cycle

Answer 3

1. Surface runoff- increased risk of flood through impermeable surfaces compared to soils
2. Polluted water- concrete and sewage can contaminate the water

Question 4

Old methods of urban drainage

Answer 4

1. Channelisation
2. Dredging
3. Dams and reservoirs
4. Flood defences

Question 5

New methods of drainage

Answer 5

1. Urban catchment management- managing urban water quality
2. SUDS- reduces potential impact of new, existing developments

Question 6

Sustainable urban drainage systems

Answer 6

• realistic + environmentally friendly replication of natural drainage
• 2 main aims: reduce surface runoff and breakdown pollutants
• Types of SUDS: wetlands, swales, paving, green roofs, retention ponds

Question 7

River restoration: Cheonggycheon river, Seoul

Answer 7

• needed because river had been badly damaged in the past and restoration needed because of decades of human alteration
  Aims: ecologically sensitive pedestrian corridor, dismantle freeway and concrete deck above stream,, improve quality of life, increase business competitiveness and connectivity
• total restored area = 5.8km
• green strip
• $281 million
• cars discouraged, bus lanes added
• 22 bridges added, 12 pedestrian
• Hanang river used as a source to mainatain flow rates - pumped in water is treated to prevent pollution

Question 8

Wetlands

Answer 8

provide stormwater attenuation and treatment
* shallow ponds and marshy areas- entirely aquatic vegetation
* slow flows to allow sediment to sttle and removes contaminates by enabling aerobic respiration
* significant ecological benefits

Question 9

London Olympic Park

Question 10

What do SUDs do?

Answer 10

1. Source control- methods reduce volume of water entering drainage network, intercepting, storing it for reuse
2. Pre-treatment- removes pollutants from surfaces before discharge e.g. trenches and ditches
3. Retention- delay discharge by providing storage e.g. ponds and wetlands
4. Infiltration- systems mimic natural recharge allowing water into ground

Question 11

Green roofs

Answer 11

covers roofs of buildings with vegetation cover/ landscaping, designed to intercept and hold precipitation, reducing surface runoff and increases transpiration

Question 12

Paving

Answer 12

allows rainwater to soak through cracks in between slabs

Question 13

Retention ponds

Answer 13

small lakes that store storm water and allow for its treatment

Question 14

Dredging

Answer 14

sediments removed from the river channel with machinery
* used as a way of stopping flooding by deepening river channel
* can cause flooding downstream
- causes water to flow more turbulently and increases speed of water flow

Question 15

Dams and reservoirs

Answer 15

manipulate water flows and stores to reduce flooding, reservoirs used as water supply
- great deal of environmental damage

Question 16

Flood defences

Answer 16

Physically altering water courses through channel straightening and flood walls
- expensive

Question 17

How did River restoration in Chenggy impact seoul environmentally, socially and economically?

Answer 17

Environmental: flood protection for 200 year period, increased biodiversity, reduces UHI effect- removal of paved express way, cooling effect on stream, increased vegetation, and increased wind speeds, reduced small particle air pollution by 35%

Social: 18.1 million visitors by 2008, 15% increase in bus ridership and 3.3% in subway, foreign tourists visit contributing to 2.1 billion, better health for locals due to reduced pollution