Water In Urban Areas Flashcards
What does a grass roof do for flooding
The green roof intercepts rain preventing the rain from running into impermeable surfaces and going into drains
What’s river straightening
Cutting through meanders to create a straight channel
This increases the gradient and speed of flow
This may also increase flood risk further downstream
What is afforestation and how does it help with flood risk
Planting trees to intercept water and reduce surface run off
Evapotranspiration from both leaves and branches dissipates water that would otherwise end up in a river
What are diversion spillways and how do they reduce flooding in urban areas
Flood relief channels that by pass the main channel , used for emergency use only , high flow levels threaten flooding or a permanent feature enhancement by creating new wetlands and recreational opportunities
What is riverbank conservation and how does it reduce flooding
Planting bushes and trees to reduce lateral erosion - the roots stabilise banks by binding the loose sediment together -
Plants absorb water on the banks- reducing amount of water that gets into the river
Decreasing erosion- the sediment won’t raise the riverbed
What is floodplain zoning and how do they reduce flood risk
Restrict land use to I certain locations on a floodplain - natural floodplains act as a natural soak way by reducing surface runoff off and impermeable surfaces being built there
What do SUDS stand for
Sustainable urban drainage systems
What is SUDS
natural processes to reduce flooding and provide something for the community to improve the look of the area
What are swales and what are the positive and negative of them
Shallow broad vegetated channels designed to store runoff and remove pollutants
Easy to incorporate into landscape
Removes water pollutants
Reduces surface run off water
Low cost
Maintenance is easy
Not suitable for steep areas or roadside parking
Limited opportunities to use trees for landscaping
What are permeable surfaces in urban environments and what are the positives and negatives of them
Permeable surfaces allow water to infiltrate across the surface by having many small holes on the surface
Reduced surface running
Reduced effect of water pollution
Can be used in high density housing developments
Do not spoil look of area
Reduced ice and puddles
Risk of long term clogging and weed growth if not properly maintained
Cannot be used where people drive more than 30 mph
What is a green roof and what are the positives and negatives of them
Plants remove urban pollutants from air
Can be applied in both density housing areas
No additional land is needed to build them
Absorbs noise pollution
Insulates buildings against temperatures of extreme heat or cold
Reduces urban heat island
High cost compared to normal roofs
Maintenance cost
Can’t instal on historic buildings
Can’t use with steep roofs
What are bioretentjon areas and what are the positive and negative effects of them
Areas of shallow landscaped depressions which have vegetation and filtration to remove pollution
Plants removing urban air pollutants
Well suited for building in areas with impermeable surfaces
Easily built in new or old housing estates
Requires maintenance
Can get clogged with weeds and litter
Not suitable for areas with steep slopes
What are rain gardens and what are the positive and negative effects of them
Small depressions in the ground that act as infiltration points for water- usually outside people’s homes
Easy to fit in to existing houses
Minimal land use
Easy to maintain
Look nice
Flexible layout - able to fit into anyone’s garden
Susceptible to clogging with litter or waste
Often small and have small impact
Cost of professional landscaping
What are retention ponds and what are the positives and negatives
Easily copes with storms and floods
Removes urban water pollutants
Creates area for wildlife
Creates area for local people to visit
Natural look adds value to area
Not suitable for densely populated areas
Invasive species spread there
Requires lots of land
Water can go stagnant and get smelly green algae
What is a sponge city
A city designed to absorb and hold rainwater
What are some benefits for a sponge city apart from its ability to prevent flooding
Provides more community green spaces
Better air quality
Improved biodiversity
What are some disadvantages of a sponge city
One disadvantage of a sponge city is that they SUDS are expensive to implement and while they may be able to cope with the issues today ,many aren’t being built with the future in mind
Why does London in particular need to become a sponge city
London is “underprepared “for climate change
Especially since floods are predicted to be 4 times more frequent because of climate change
London is only 22 percent spongelike
