Urban Drainage

Question 1

What are infiltration rates like in urban areas?

Answer 1

Infiltration rates are low as there are so many impermeable surfaces so groundwater stores are low.

Question 2

How surface runoff affected by precipitation and storms in urban areas more?

Answer 2

Urban areas have more precipitation due to the UHI effect which increases surface runoff.

Question 3

What is catchment management?

Answer 3

Managing rivers and improving drainage systems at a whole river catchment
Aims to minimise:
-flooding
-drought
-water pollution
-erosion
but increase river ecosystems.

Question 4

What methods of hard engineering can be used to manage river catchments?

Answer 4

-Dams
-Floodwalls
-Reservoirs
Prevent flooding and ensure a constant water supply.

Question 5

What are the negatives of hard engineering methods to manage river catchments?

Answer 5

-Expensive
-Disrupt natural systems
Eg: Silt can get trapped behind dams starting downstream areas increasing erosion.
-Alter wildlife habits.

Question 6

How can soft engineering be used to manage a river catchment?

Answer 6

Uses knowledge of the river basin and its processes to work with nature.
-Land use management
Eg: planting trees to decrease flood risk and pollution.
-River restoration.

Question 7

Evaluate the use of soft engineering to manage a river catchment.

Answer 7

+Cheaper than hard engineering.
+Improved local environment
-Land use management can be difficult in areas already urbanised.

Question 8

Why might water management decisions create conflict?

Answer 8

What is the best for the catchment may not be best for all individuals so some residents may feel ignored.

Question 9

Give an example of a catchment management scheme that was disruptive.

Answer 9

The three gorges dam in China flooded residential areas forcing 1.2 million people to move.

Question 10

What is SUDS?

Answer 10

Sustainable urban drainage systems

Question 11

What do SUDS aim to do?

Answer 11

Imitate natural drainage systems rather than channeling water through pipes and drains using several methods.

Question 12

What are the methods SUDS use?

Answer 12

-Vegetated trench’s
-Vegetated roofs
-Containers

Question 13

How do vegetated trenches make urban drainage more sustainable?

Answer 13

Increased interception of rainfall and retention basins store water. They increase infiltration and water storage decreasing runoff and channel flow lowering flood risk and the amount of pollutants entering the river.

Question 14

How do vegetated roofs reduce flood risk?

Answer 14

They intercept rainfall and increase evapotranspiration which reduces flood risk.

Question 15

How do containers on roofs decrease flood risk?

Answer 15

Containers catch and store rainwater for reuse decreasing flood risk and water can also be used during droughts.

Question 16

Why are SUDS more sustainable than traditional urban drainage?

Answer 16

They work with the natural environment to improve drainage and water quality while providing new habitats and increasing biodiversity.

Question 17

What is the example for river restoration?

Answer 17

Enfield in London

Question 18

What are the sims of river restoration in Enfield?

Answer 18

-reduce flood risk
-decrease water pollution
-create new habitats
-increase biodiversity

Question 19

How common are floods in Enfield?

Answer 19

Approximately 1 large one per year.

Question 20

How many homes are at risk of flood?

Answer 20

Over 9000

Question 21

What are the sources of water pollution into the river Lea?

Answer 21

-Surface runoff washes oil and heavy metals into the water.
-Domestic sources
10% of houses in Enfield have wastewater pipes that feed directly into the river.

Question 22

When did the river restoration project begin in Enfield?

Answer 22

2012

Question 23

What were the aims of the river Lea restoration project?

Answer 23

-Reduce flood risk
-Reduce surface runoff to increase water quality
-Provide more habitats for wildlife
-Create new recreational areas for residents

Question 24

What SUDS did the restoration project use?

Answer 24

-Vegetated trenches
-Rain planters
-Wetlands

Question 25

How were vegetated trenches used in Enfield?

Answer 25

Trenches have been dug around roads to absorb runoff and decrease flood risk.

Question 26

How have rain planters been used in Enfield?

Answer 26

Installed in schools to collect rainwater and manage the flow of water into the drains to reduce flood risk.
+Provided opportunities to educate children on water management.

Question 27

How have wetlands been used in Enfield?

Answer 27

Reed beds were created around the salmons Brook to decrease runoff and filter water before it enters the river.

Question 28

Who provided funding for the river lea restoration project?

Answer 28

Defra and Thames water granted £340,000 to construct more SUDS.

Question 29

What were the reactions from the community to the river Lea restoration project?

Answer 29

Positive
Community helps with litter pickups too!

Question 30

How have local schools been involved in the project?

Answer 30

Thames21 offered education sessions for local schools to increase engagement which involved 1000 students in litter picking and wildlife management.

Question 31

How has the river Lea restoration project been successful?

Answer 31

-Flood risk is reduced
-SUDS have reduced ammonia levels in salmons brooks by 67%
-Populations of eels and dragonflies have increased.