Urban precipitation and drainage management

Question 1

On average what percentage more precipitation does urban areas experience compared to rural areas?

Answer 1

5-15% more

Question 2

Why is there more precipitation in urban areas compared to rural areas?

Answer 2

• warmer air in cities can hold more moisture
• dust and pollution make more condensation nuclei

Question 3

How much precipitation is surface run of is in rural, suburban and central urban in percentages?

Answer 3

rural- 10%
Suburban- 30%
Central urban- 55%

Question 4

Why are drains needed in urban areas?

Answer 4

Impermeable surfaces like concrete stops water infiltrating into the ground causing surface runoff so drains are needed to remove water quickly to reduce flooding

Question 5

Name 4 hard engineering strategies to reduce flooding in urban areas.

Answer 5

river straightneing
natural levees
diversion spillways
river channelisation

Question 6

What is river straightening and how does it prevent flooding?

Answer 6

straightening the channel to allow water to flow rapidly to prevent it from flooding

Question 7

What is natural levees and how do they prevent flooding?

Answer 7

banks either side of the river which can be made higher to create embankments which can hold back flood water in the river to reduce flooding

Question 8

Whats diversion spillways and how do they prevent flooding?

Answer 8

They are flood relief channels which bypass the main channel which are only used for emergencies and are controlled by gates in order to move water quickly if the channel gets full and creates a flood risk

Question 9

What is river channelisation and how does it prevent flooding?

Answer 9

like river straightening but uses concrete which reduces friction so it increase the rate of flow

Question 10

What are the 2 disadvantage of river straightening?

Answer 10

• may increase flood risk downstream
• may cause more erosion and will destroy natural habitats

Question 11

What is a disadvantage of river channelisation?

Answer 11

it damages the local ecosystems and looks unsightly

Question 12

What are the 4 soft engineering strategies to reduce flooding in urban areas?

Answer 12

afforestation
riverbank conservation
floodplain zoning
river restoration

Question 13

What is afforestation and how does it prevent flooding?

Answer 13

planting trees which interrupts the flow of water and helps soak up the water and through evapotranspiration get rid of it into the atmosphere

Question 14

What is riverbank conservation and how does it prevent flooding?

Answer 14

planting bushes and trees to reduce lateral erosion, this is because their roots stablise the banks to reduce flooding

Question 15

What is floodplain zoning and how does it prevent flooding?

Answer 15

It restricts different land uses to different parts of the floodplain to stop urban areas from being flooded as floodplains are there to store flood water and not to be built on

Question 16

What is river restoration and how does it prevent flooding?

Answer 16

it involves returning a river to its natural cause

Question 17

What does SuDS stand for?

Answer 17

sustainable drainage system

Question 18

What are SuDS?

Answer 18

realistic yet environmentally friendly replication of natural drainage systems in any built environment as they hold back and slow surface run off from developments and allow natural processes to break down pollutants

Question 19

What are swales?

Answer 19

wide, shallow drainage channels that are normally dry

Question 20

What are permeable road and pavement surfaces?

Answer 20

the use of porous block paving and concrete to allow the infiltration of water into the ground

Question 21

What are infiltration trenches?

Answer 21

gravel filled drains and filter strips

Question 22

What are bioretention basins?

Answer 22

gravel and/or sand filtration layers beneath reed beds and other wetland area to collect, store and filter dirty water

Question 23

What are detention basins?

Answer 23

excavated basins to act as holding ponds for water storage during flood events

Question 24

What are rain gardens?

Answer 24

shallow landscape depressions planted with flowers and shrubs

Question 25

What are green roofs?

Answer 25

super-insulating wildflower habitats with minimal runoff to gutters

Question 26

What are the benefits of SuDS?

Answer 26

• slow down surface run off and reduce the risk of flooding
• prevent water pollution
• provide valuable habitats for wildlife in urban areas
• create green spaces for people in urban areas

Question 27

What SuDS did Lamb Drove, Cambourne use?

Answer 27

green roof
permeable paving
swale
retention pond
filter strip
detention basin
water butt

Question 28

Why did Lamb Drove, Cambourne build SuDS?

Answer 28

It had a development of 35 ‘affordable’ homes on the floodplain where flooding was a major concern- the SuDS have added social value to both residents and community while improving the biodiveristy and ecology of the area.