Contemporary Urban Environments - Urban Drainage

Question 1

What is the Thames Tideway, London?

Answer 1

• A new 25km sewage system built underneath the River Thames to capture, store and transfer any excess sewage and rainwater that usually flows into the river.
• Will help reduce the amount of untreated sewage that is released into the Thames.
• Cost $4.2 billion (funded by Thames Water).
• Started in 2016 and aims to be completed by 2025.
• Increased levels of noise and air pollution, congestion and many believe green infrastructure would have been sufficient.

Question 2

What is the case study for river restoration and conservation?

Answer 2

Cheonggyecheon river, Seoul, South Korea

Question 3

What is urban precipitation like?

Answer 3

Precipitation is higher in urban areas than in rural areas and storms are more intense, this is due to the urban heat islands effect and the formation of condensation nuclei from dust and pollutants

Question 4

How do urban surface affect drainage?

Answer 4

Urban areas are covered in impermeable materials e.g. concrete and tarmac, this results in low infiltration and high surface run-off

Question 5

What are the charcteristics of an urban river catchment?

Answer 5

• Water is artificially imported into the system adding extra water as an INPUT
• Runoff is poor quality as it picks up dust and pollutants created by urban processes like industry or transport
• An artificial drainage system is added via a network of underground pipes and rains used to get rid of rainwater in urban areas
• Less water stored in urban areas as lakes and ponds are often drained and water is channelled underground.

Question 6

What are the characteristics of an urban hydrograph?

Answer 6

Low infiltration rates, high surface runoff and channelling of water means that water enters rivers quickly. This gives a short lag time and high peak discharge, with a fast return to base flow

Question 7

What is catchment management?

Answer 7

Catchment management is a way of managing rivers and improving drainage systems by looking at the whole river catchment, and the interactions between water and land. It aims to minimise issues such as flooding, drought, water pollution and erosion in sensitive areas, and to improve river ecosystems.

Question 8

How is hard engineering used in catchment management?

Answer 8

Dams, floodwalls and reservoirs, which are used to prevent flooding and ensure a constant water supply. However, these schemes can be expensive, disrupt natural systems and alter wildlife habitats.

Question 9

How is soft engineering used in catchment management?

Answer 9

Land use management, river restoration and conservation. It is generally cheaper than hard engineering and it can improve the local environment.

Question 10

What are SUDS?

Answer 10

SUDS aim to imitate natural drainage systems, rather than channelling water through pipes and drains

Question 11

What are some characteristics of SUDS?

Answer 11

• Vegetated trenches (swales) – increase interception of rainfall, and retention basins store water. They help to increase infiltration and water storage, this decreases runoff and channel flow, which lower flood risk.
• Vegetated roofs – intercept rainfall and increase evapotranspiration, which reduces the flood risk
• Containers on the roofs of buildings catch and store rainwater for reuse. This helps reduce drought risk.

Question 12

How are SUDS sustainable?

Answer 12

SUDS are more sustainable than traditional urban drainage methods because they work with the natural environment to improve drainage and water quality. Vegetated trenches and roofs also provide new habitats and increase biodiversity.