1.6 Urban drainage

Question 1

Why is it so important to have a good urban drainage system

Answer 1

As stated in Urban climate, urban areas experience more severe weather, and have higher populations, meaning they are vulnerable

Question 2

What is Urban hydrology (the urban water balance)

Answer 2

Urban hydrology displays the relationship between of processes in the water cycle, such as flows, stores and outputs much like drainage basin would.

But with less infiltration and evapotranspiration, and more runoff and waste, due to urban infrastructure

Question 3

What are the features (and issues) of urban hydrology

Answer 3

1. More intense rainfall and storms
2. Reduced evapotranspiration and infiltration
3. Impermeable surfaces increase runoff
4. Runoff increases flooding and REDUCES WATER QUALITY + BIODIVERSITY

Question 4

What are the features of an urban hydrograph compared to a rural hydrograph

Answer 4

They have a low base flow
They have a short lag time
They have a high peak discharge (causing steep rising limbs)

Question 5

What are the 3 main type of urban drainage systems

Answer 5

Smooth storm sewer systems (most common)
Urban catchment management and SUD’s
River restoration

Question 6

How do smooth storm sewer systems work and why are the not sustainable

Answer 6

These are smooth, plastic, underground pipes, from which water is rapidly transferred from cities to streams.

Lots of the water goes into the streams as runoff, increasing flood risk. Not as much water is stored in plants/soil, increasing drought risk. It also effects the rivers ecosystem and human’s drinking water

Question 7

What is Urban catchment management

Answer 7

The management of urban water within an urban drainage basin

Question 8

What do SUD’s aim to do

Answer 8

SUD’s aim to replicate the natural patterns of drainage systems to have minimal environmental impact, while being cost effective

Store runoff, allow it to soak and slowly transport to filter out pollutants

Question 9

Give some examples of SUD’s methods and some where they are being used

Answer 9

Blackpool

Green roofs
Water butts
Retention ponds (270m of water)
Planting and reworking soil

Question 10

Give an example of a hard engineering river solution with context

Answer 10

The LA river

Over 100,000 people in LA are at flood risk

in 1930, they concreted 51 miles along the river to convert the meanders into a nice controlled flow.

Question 11

What were the advantages and disadvantages of the LA river

Answer 11

Reduced flooding (efficient)
Easy to maintain

Ugly, destroyed ecosystems
If one part breaks, whole system is at risk

Question 12

Give an example of a soft engineering river solution

Answer 12

Cheonggyecheon, Seoul

Question 13

Why did Cheonggyecheon need restoration

Answer 13

In the 20th century, the river was completely covered over by a freeway

This drastically affected the urban drainage catchment, and caused issues for both humans and wildlife. It also created a north and south divide, causing 100,000 businesses to struggle

Question 14

What were the aims of the Cheonggyecheon restoration project

Answer 14

In 2003, 5.8km of the river was turned into an ecologically sensitive green corridor to improve economic, social and environmental opportunities

Question 15

What did the Cheonggyecheon restoration involve

Answer 15

Added 22 bridges and lots of seating to improve connectivity and business

Dismantled the freeway above it

Split into 3 zones - the middle zone has water falls to increase oxygen supply, and the final zone looks overgrown and wild to look natural

Question 16

What were the impacts on the river catchment after Cheonggyecheon’s restoration (economic, social, environmental)

Answer 16

1. Land prices have increased up to 50% in areas within very close proximity
2. Foreign tourists have spent a total of $2 million
3. Amount of people who ride buses have increased
4. Less likely to suffer form respiratory issues
5. Flood protection and reduced urban heat island
6. Reduced small particle pollution by 35%