Urban Drainage Flashcards
What is the traditional method of removing surface water run off?
Traditionally, a network of underground pipe systems were used to remove surface water run off.
What is a problem with traditional water drainage systems?
They did not take into account how useful the water could be.
What are some of the potential uses water could have?
Water resource management.
Provided a habitat for wildlife.
Landscaping
Community facilities
List 3 natural landscapes:
Forests
Wetlands
Grasslands
What do natural landscapes do?
They trap precipitation.
What do natural landscapes allow?
They allow precipitation to infiltrate the ground.
True or false: urban areas have natural landscapes to trap precipitation and allow it to infiltrate the ground?
False: urban areas do not have areas like this.
Instead of natural landscapes, what do urban areas have?
They have impermeable surfaces like roads, car parks and rooftops.
What does SUDS stand for?
Sustainable Urban Drainage Systems
What are SUDS?
These are modern approaches to urban drainage. They are a more holistic approach and try to manage surface water and mimic natural drainage.
Where do greater and more intense amounts of precipitation tend to fall?
Greater amounts of intense rainfall tend to occur in cities rather than the surrounding rural area.
Where are pollutants from urban areas going?
They get into rivers and into the ground which is bad because ground water pollution is hard to clean up.
What are 3 adaptations of urban areas in regards to water shedding?
Sloping roofs
Smooth rounded guttering
Cambered roads
What acts like high density drainage systems?
Storm sewer systems collect water and act like high density drainage systems.
What gathers speed and erosional power the further underground it travels?
Water
What happens when water leaves the storm drains?
The water empties into streams which fill rapidly.
What two things are reduced because of reduced infiltration?
Soil water and groundwater levels.
What type of water feeds streams during dry periods?
Soil water and groundwater.
What is reduced in streams as a result of a lack of soil water and groundwater?
The base level flows.
What does a storm hydrograph for an urban river show?
A river with a flashy discharge but a low base flow.
What are urban areas more likely to have after heavy rainfall?
They are more likely to have flooded rivers.
Why are more people now at risk of flooding?
The increase of population and urban growth as well as more frequent severe weather because of climate change will lead to more people being at risk to flooding.
According to the Asian Development Bank, how much of the Asian population will be at risk to flooding by 2025?
350 million people in Asia will be at risk from inland flooding by 2025.
What has the Red Cross stated about almost half of the natural disasters that it dealt with in 2014?
Almost half of the natural disasters that the Red Cross dealt with in 2014 were caused by floods.
What can a high river flow cause?
This can cause a flooding and erosion of the river bank during wet periods.
What will a decreased river flow during dry weather cause?
This will cause harm to fish and other aquatic life.
What can high water temperatures do to ecosystems?
They can disturb ecosystems.
What can very high flows do?
They can overload the foul water system resulting in raw sewage on the surface.
What are 6 causes of water pollution?
Road salt Viruses from pet waste Pesticides and nutrients Heavy metals Oil, grease and toxic chemicals Sediment
Where do the polluting pesticides and nutrients come from?
They come from parks and gardens.
Where do the polluting heavy metals come from?
Car exhausts.
Where do the oil, grease and toxic chemicals come from?
They come from cars.
Where does the sediment come from?
River bank erosion and building sites.
What can pollutants do?
Harm fish and wildlife.
Kill native vegetation.
Foul drinking water supplies.
Make recreational spaces unsafe and unpleasant.
How can sediment from erosion reduce habitats?
It can fill in spaces between the rocks on the stream bottoms which reduces living space for biological communities.
What is the Los Angeles River channel designed to be?
It is designed to be fail-safe.
What happened in to the LA River in the 1930s which caused authorities to control and channelize it?
Devastating flash flooding in the 1930s caused authorities to convert it from natural and meandering to cement and controlled.
What is one advantage of the channelized LA River?
The channel has helped to control flooding.
What are two disadvantages of the LA River having a channel?
It removed the ecosystem services that the river used to provide and the river may also be compromised I one part of the channel sustains significant damage.
What type of engineering is the channelling?
Hard engineering.
What is an alternative to hard engineering?
Safe-to-fail measures.
What title do safe-to-fail methods generally fall under?
They generally fall under the title of SUDS.
How do SUDS work?
Rainwater is collected in water butts for use in gardens or flows into grass channels called swales where it then travels onto grass basins where it is stored before being released into local ditches.
Where does rain that falls on roads go to before joining the rest of the SUDS system?
It soaks though a permeable block paving where it is either filtered and stored in the stone below or flows into swales with stone filter drains underneath before joining the rest of the SUDS system.
What do source control SUDS deal with?
These deal with surface run off on or near to where the land falls.
What do site control SUDS deal with?
These deal with surface run off from larger areas such as roads.
What do regional control SUDS deal with?
These deal with run off from a large area, usually downstream of source and site controls.
Give an example of where SUDS have been used.
Moor Park Centre in Bispham, North Blackpool
What are the knock-on benefits of SUDS?
They prevent puddles forming which therefore means that dangerous ice is less likely to form.
What affects the seasonal and yearly variations of water flow?
Dams
What is a good example of a sustainable river project?
The Cheonggyecheon River project, Seoul, South Korea
What is the population of Seoul?
24.5 million
What was built over the course of a small seasonal stream in Seoul?
A central area in the city called Cheonggyecheon.
When was the stream in Cheonggycheon covered up?
Between 1958-1961
What was built on top of the small seasonal stream?
A major road.
When was the scheme to improve the situation launched?
2003
Why was the stream originally covered up?
It was seen as a flood and sanitation risk.
How much was spent on restoring the river?
$281 million
What was the river transformed into?
It was transformed into a 5.8km ecologically sensitive green pedestrian corridor.
What is South Korea now putting a large emphasis on?
It is now putting more of an emphasis on sustainability, health and social responsibility which is why it launched the scheme.
How many bridges were built?
22
Out of the bridges built, how many were pedestrian?
12 were pedestrian.
Out of the bridges built, how many were for vehicles?
10
Why were the bridges built?
They were built to improve the connectivity between the city’s north and south sides.
From which river is water pumped to create a constant flow of water?
Water is pumped from the Hanang River to create a constant flow of water.
What were two concerns during the restoration?
Traffic disruption
Loss of business
What did Seoul Metropolitan authority do to address these concerns?
Provided extra parking with lower fees.
Improved loading and unloading systems.
Promoted the businesses in Cheonggyecheon.
Provided businesses with restructuring grants.
What wasn’t impacted as much as expected?
The traffic
What was the temperature reduction as a result of the road being removed?
2.5C
What has been re-established?
The habitat that would have once been in the stream was re-established and the area has become an urban wildlife haven.
Why did the elongated freeway need to be removed?
It was old and posed a safety risk so it needed to be repaired or removed.
What is a catchment?
This is something for collecting/ catching water like a reservoir or a natural basin.
What do concrete storm drains do to the peak discharge and the lag time on a hydrograph?
They increase the peak discharge and decrease the lag time.
What are the 3 different types of natural water storage?
Vegetation
Surface storage
Groundwater storage
What else does vegetation include concerning natural water storage?
It includes interception and intercepted storage.
What are three examples of surface water storage?
Ponds, lakes, puddles.
What are two key things associated with ground water storage?
The water table.
Water is absorbed through soil and permeable rock.
What does a hydrograph show?
It shows the rate of flow (discharge) versus the time past a specific point in a river or other channel carrying flow.
What is precipitation measured in?
mm
What is the peak rainfall?
This is the time of highest rainfall.
What is the peak discharge?
The time when the river or channel reaches its highest flow.
Why is the peak discharge later?
This is because it takes time of the water to find its way to the river or channel.
What is the lag time?
This is the time it takes for the water to find its way to the river or channel.
What does the falling limb show?
This shows that the water is still reaching the river or channel but in decreasing amounts.
What was the percentage of surface run off before urban development?
It was 1%
What is the percentage of surface run off since urban development?
20-30%
