Cue 7 Urban Drainage Flashcards
What are urban areas usually covered in
Impermeable materials like concrete or tarmac
Urban structures are designed to shed water quickly what does this result in
Low infiltration and so replenishment of groundwater stores is low
What does ground water feed and what happens during dry periods
Groundwater feeds rivers so during drier periods river discharge in urban areas is low
Precipitation and more intense storms is higher in urban areas what does this cause
Increased surface run off
What happens to surface run off
It is channeled through man made pipes which transports water to rivers and streams
What is the result of low infiltration rates, high surface run off and channeling of water
It enters rivers quickly and gives a short lag time and high peak discharge with a fast return to base flow
What is catchment management
A way of managing rivers and improving drainage by looking at the whole river catchment and the interaction between water and land
What is the aim of catchment management
To minimize issues like flooding, drought water pollution and erosion and to improve river ecosystems
What are the 2 methods to manage river catchments
1 hard engineering and soft engineering
Describe hard engineering
These involve man made structures like dams, flood walls and reservoirs to prevent flooding and ensure a constant water supply
What are the disadvantages of hard engineering
Expensive
Disrupt natural systems
Alter wildlife and habitats
Describe soft engineering
Uses the knowledge of the river basin and its processes to try to work with nature
Uses land management and involves river restoration and conservation
It is cheaper and can improve the environment
Disadvantages of soft engineering
Planning restrictions can limit the construction of new homes and businesses
Who makes the decision about which method of land management to use and why
Experts and not residents as they look at what is best for the catchment as a whole - residents and communities often feel ignored
Give an example of how catchment management systems can be disruptive
3 Gorges Dam in China flooded 13 cities and 140 towns forcing 1.2 million people to move
What is th aim of sustainable urban Drainage systems (SUDS)
To limit natural drainage systems rather than channeling through pipes or drains
What methods do SUDS use to decrease flooding, water pollution and drought in urban areas
1 vegetate trenches increase interception of rainfall and retention basins store water. They help to increase infiltration and water storage- this decreases runoff and channel flow which lowers flood risk. Increased infiltration decreases the amount of pollutants entering watercourses
2vegetate roofs intercept rainfall and increase evapotranspiration which reduces flood risk
3containers on the roofs of buildings catch and store rainwater for refuse helping to reduce drought risk
Why are SUDS more sustainable than traditional urban drainage methods
They work with the natural environments to improve drainage and water quality- vegetate trenches and roofs provide new habitats and increase biodiversity
