🌆3.2.3.5 - Urban Drainage

Question 1

What is interception?

Answer 1

When precipitation lands on buildings, vegetation, concrete etc before it reaches the soil. Storage is temporary, often quickly evaporated

Question 2

What is vegetation storage?

Answer 2

All the moisture in vegetation at one time

Question 3

What is surface storage?

Answer 3

Total volume of water held on Earth’s surface in lakes, ponds and puddles

Question 4

What is groundwater storage?

Answer 4

Water in underground permeable rock strata

Question 5

What is channel storage?

Answer 5

Water held in a river or stream channel

Question 6

How can flooding be increased in urban areas?

Answer 6

If run off from roofs and paved areas is piped into waterways

Question 7

What are SUDS?

Answer 7

Sustainable Urban Drainage Systems

Question 8

What do SUDS aim to do?

Answer 8

Control the quality and rate of run off from a development
Improve quality of run off
Enhance the nature conservation, landscape and value of site and surroundings

Question 9

What are permeable pavements?

Answer 9

Pavements made of porous material such as concrete blocks, porous asphalt and crushed stone

Question 10

Where does water go from a permeable pavement?

Answer 10

It may infiltrate directly into the subsoil or be stored in an underground reservoir before soaking into the ground

Question 11

What are swales?

Answer 11

Shallow ditches with gently sloping sides that can be built into the landscape

Question 12

What are the advantages of swales?

Answer 12

They provide temporary storage for storm water
Reduce peak flows
Facilitate filtration of pollutants
Encourage microbial decomposition

Question 13

How can green roofs act as SUDS?

Answer 13

They reduce flow rates and improve water quality, as well as improving insulation

Question 14

What are infiltration trenches?

Answer 14

Stone filled reservoirs to which stormwater run off is redirected

Question 15

How are pollutants removed from infiltration trenches?

Answer 15

By absorption, filtering and microbial decomposition in the surrounding soil

Question 16

What does the type of SUDS in place depend on?

Answer 16

The pollutants present in run off
The size of and drainage strategy for the catchment area
The hydrology of the area and infiltration rate of soil
The presence of Groundwater Source Protection Zones or contaminated land

Question 17

What do SUDS aim to do?

Answer 17

Drain surface water in a manner that will provide a more sustainable approach than what has been standard practice of re-routing run-off through a pipe to a water course

Question 18

What percentage more precipitation do urban areas receive than rural areas?

Answer 18

5%

Question 19

Causes for increased levels of precipitation in urban areas

Answer 19

. Urban Heat Island
. Cities produce large amounts of water vapour (industry)
. Less vegetation
. Impermeable surfaces
. Pollution

Question 20

Causes of increased precipitation: Urban Heat Island

Answer 20

. Increased temperature = increased evapotranspiration
. Warmer air holds more water

Question 21

Causes of increased precipitation: Less vegetation

Answer 21

. Decreased evapotranspiration = decreased moisture in air
. Decreased infiltration rates

Question 22

Causes of increased precipitation: Impermeable surfaces

Answer 22

. Water quickly transported (drains and gutters)
. Increased surface runoff causing short lag time and increased peak discharge

Question 23

Why do impermeable surfaces create issues for local geology

Answer 23

. Rock below doesn’t get water
. Clay goes brittle
. Impacts house foundations

Question 24

Causes of increased precipitation: Pollution

Answer 24

Increased cloud formation due to more condensation nuclei

Question 25

Problems with decisions being made by experts when it comes to water management solutions

Answer 25

Residents feel ignored
Feels disruptive i.e. Three Gorges Dam

Question 26

Issues with traditional methods of urban drainage

Answer 26

. Increased river flow- increased flood risk
. Raw sewage leaks into rivers in high flows
. Road salt, oil, toxic chemicals washes off urban surfaces and enters rivers
. Pet waste = viruses

Question 27

Why are SUDS considered a better way to manage urban drainage?

Answer 27

. Work with natural environment
. Improve drainage and water quality
. Some methods increase biodiversity as they create new habitats

Question 28

Swales

Answer 28

. Temporary storm water storage
. Decrease peak flows
. Filter out pollutants
. Increased infiltration
. Installed next to roads instead of curbs

Question 29

Wetlands and Ponds

Answer 29

. Accommodate water level variation
. Increased flood storage capacity
. Plants and algae filter out pollutants
. Silt traps decrease sedimentation

Question 30

Permeable Pavements

Answer 30

. Porous pavements i.e. concrete blocks increase infiltration
. Direct infiltration or stored underground
. Removes pollutants in the infiltration process

Question 31

Infiltration Trenches

Answer 31

. Stone-filled reservoirs
. Runoff directed into them, gradually infiltrates
. Filter strips removes excess solids and pollutants

Question 32

SUD example

Answer 32

Alcester primary care centre

Question 33

What SUDs are used

Answer 33

Soakways, swales, raingardens, permeable pairings

Question 34

What are the benefits of the SUDs

Answer 34

. Environment benefits staff and patiences
. Control of surface runoff
. Water treated biologically through the system
. Biodiversity increases
. Lower cost of installation

Question 35

Why is precipitation higher in urban areas

Answer 35

. Increased presence of hygroscopic nuclei
. Warmer air in cities can hold more moisture
. There is less vegetation in urban areas and therefore less evapotranspiration
. High surface run off

Question 36

How much more precipitation do urban areas get than rural areas?

Answer 36

5-10%

Question 37

Answer 37

Swales

Question 38

Answer 38

Permeable pavements

Question 39

Answer 39

Infiltration trench