Urban Drainage Flashcards
What percentage more precipitation do urban areas receive than rural areas?
5%
Causes for increased levels of precipitation in urban areas
Urban Heat Island Cities produce large amounts of water vapour (industry) Less vegetation Impermeable surfaces Pollution
Causes of increased precipitation: Urban Heat Island
Increased temperature = increased evapotranspiration
Warmer air holds more water
Causes of increased precipitation: Less vegetation
Decreased evapotranspiration = decreased moisture in air
Decreased infiltration rates
Causes of increased precipitation: Impermeable surfaces
Water quickly transported (drains and gutters)
Increased surface runoff causing short lag time and increased peak discharge
Why do impermeable surfaces create issues for local geology?
Rock below doesn’t get water
Clay goes brittle
Impacts house foundations
Causes of increased precipitation: Pollution
Increased cloud formation due to more condensation nuclei
Problems with decisions being made by experts when it comes to water management solutions
Residents feel ignored
Feels disruptive i.e. Three Gorges Dam
Issues with traditional methods of urban drainage
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
Why are SUDS considered a better way to manage urban drainage?
Work with natural environment
Improve drainage and water quality
Some methods increase biodiversity as they create new habitats
Swales
Temporary storm water storage Decrease peak flows Filter out pollutants Increased infiltration Installed next to roads instead of curbs
Wetlands and Ponds
Accommodate water level variation
Increased flood storage capacity
Plants and algae filter out pollutants
Silt traps decrease sedimentation
Permeable Pavements
Porous pavements i.e. concrete blocks increase infiltration
Direct infiltration or stored underground
Removes pollutants in the infiltration process
Infiltration Trenches
Stone-filled reservoirs
Runoff directed into them, gradually infiltrates
Filter strips removes excess solids and pollutants
