3.2.3 contemporary urban environments Flashcards
1
Q
Why do we study contemporary urban environments?
A
- From 2007 to 2008 there are now more urban environments then rural dwellings
- To prevent economic social inequality
- Cities, change and develop over time and buildings have changed
- Teaches us how to use green space and landscapes
- Weather and climate
- People, and then movement (who, what and why)
- Sustainability e.g. waste, transport and derelict buildings
2
Q
What is urbanisation?
What is urban growth?
What is urban expansion?
A
Urbanisation is the increase in the proportion of people living in urban areas
Urban growth is the increase in total population of a town or city over a period of time
Urban expansion is the increase in size or geographical footprint of a city
3
Q
What is a mega / meta city?
A
Mega city = metropolitan area with a total population in excess of 10 million people
Meta city = urban areas that have merged to form continuous built-up areas with more than 20 million people
4
Q
Describe urbanisation
A
urbanisation is an uneven process
in 1800, only 3% of the world’s population lived in cities. Rose to 47% by the 20th century.
UN forecasts that the global urban population of 3.2 billion will rise to nearly 5 billion by 2030
3/5 of people will live in cities
most urban growth about 25 years will be in LICs
1/7 of the world’s population live in shanty towns
5
Q
Urbanisation analysis
A
- Urbanisation started increasing in the 1800s
US was the first to urbanise the quickest
India progressed the slowest along with China - Overall increase in urban and rural areas
In 2000, rural population started slowing with urban population increasing
In 2007, urban population over took rural - northern hemisphere = majorly urban population
southern hemisphere = majority rural hemisphere
LICs have more rural areas
6
Q
what is suburbanisation?
A
suburbanisation is the movement of people from living in the inner parts of the city to living on the outer edges
7
Q
describe the process of suburbanisation in the UK
A
- The towns and cities in the UK demonstrate the effects of past suburbanisation. In the 1930s there were few planning controls and urban growth took place alongside main roads = ribbon development.
- By the 1940s this growth, and growth between the ribbons, became a cause for concern. This led to the creation of green belt-areas of open space and low density land use around towns where further development was strictly controlled
- Since 1950, suburban expansion has increased and has been better planned. During the 1950s and 60s large-scale construction of council housing took place on the only land available, which was the suburban fringe
- In the 1970s, there was a move towards homeowner ship, which led to private housing estates being built, also on the urban fringe. Building in these areas allowed people to have more land for gardens and more public open space
- As car ownership grew, the edge of town, where there is more land available for car parking and expansion, became the favoured location for new offices, factories and shopping outlets. In a number of cases, the strict controls of the green belts was ignored
- In recent years new detached and semi-detached houses and bungalows have been built in suburban areas, along with local shopping centres and schools
8
Q
what are the causes of suburbanisation?
A
- attractions:
pleasant environment
greenspace
room to expand
restaurants/entertainment - decline:
slum clearance - technology:
ICT and computer developments, means more people work from home
Advances in transport - people can commute longer distances
4, de-industrialisation:
inner cities experienced spatial problems
loss of manufacturing jobs in the city - workers lacked skills to work in the service sector
- de-centralisation:
shift of jobs into service sector
non-centralised locations - cheaper land prices
9
Q
what are the effects of suburbanisation?
A
- Urban sprawl - leaves a hole in the CBD as people move out to the suburbs
- Better sense of community and more family orientated in the suburbs
- Increase in and out of city congestion and air pollution - 40% travel by car and increase in commuting
- Increase pressure on the greenbelt
- Increased demand for local retailing and increased employment opportunity
- Increased amount of derelict and empty buildings in the CBD
10
Q
what is ethnic enclaves?
A
a geographical area where a particular ethnic group is spatially clustered and socially and economically distinct from the majority group
11
Q
what are dormitory settlements?
what are edge cities?
A
dormitory settlements = where many commuters sleep overnight but travel to work elsewhere during the day
edge cities = concentration of business, shopping and entertainment outside a traditional downtown
12
Q
what are the global patterns of 1945?
A
Urbanisation = An increase in the proportion of a country’s population living in a town or city. The drawer of urban areas can often be due to better economic opportunities, centres for education, access to more reliable food supplies and clean water. Additionally, people may be drawn to urban living as a lifestyles found there are more attractive to them.
Suburbanisation: people are attracted to less densely populated areas with more open space, greenery, and driveway parking. The growth of lower density housing developments are often closely linked to road and public transport networks, which shorten travel time into the cities. People choosing to live on the edge of the cities can lead to urban sprawl.
Counter-urbanisation: people moving away from the city can be due to a range of urban push factors, such as crime, traffic congestion, degradation of the city buildings and spaces. Environmental push factors such as a lack of green space and air pollution can also be a reason for people moving out of cities and into more rural villages.
Urban resurgence: The improvement of city buildings leads to people being pulled into life in the city centre - this especially is centred for young professionals, graduates, students. The influx of wealth and youth leads to the revival and regeneration of some inner city. This then leads to more people returning
13
Q
describe these terms:
natural increase
fertility rate
birth rate
death rate
A
natural increase = birth rate minus the death rate of a population
fertility rate = the number of lives birthed per 1000 women of a child-bearing age
birth rate = the number of births a year per 1000 population
death rate = the number of deaths a year per 1000 population
14
Q
what is counter urbanisation?
A
the process of people moving away from urban areas to smaller settlements and rural areas - often leap frogging the green belt
depopulation of major urban areas to small areas - leads title growth of rural areas beyond the city
boundary between rural and urban becomes less obvious as more people become involved
15
Q
what are the social characteristics of counter urbanisation?
A
hobby farmers replace traditional agricultural life
suburban villages have a mixture of traditional dwellers and commuters
segregation of new migrants (commuters) and old rural residents
highly mobile population
16
Q
who is involved in counter urbanisation?
A
middle aged families
young professionals
existing rural dwellers
affluent people moving of their own accord
17
Q
what has caused counter urbanisation?
A
negative reaction to city life
air pollution
aspirations of a quiet country life
land and house prices are cheaper
higher personal car ownership and increase in public transport
working from home
improved roads
18
Q
what are the push factors of counter urbanisation?
A
air pollution
increasing house prices
traffic congestion
crime rates
social changes
19
Q
what are the social effects of counter urbanisation?
A
- newcomers may not appreciate the traditional values of village life
- there may be some conflict with new residents
- rural services may close and use services in city instead
- people left behind are usually working class
20
Q
what are the economic effects of counter urbanisation?
A
- young cannot afford to buy in the village, causes resentment
- old properties are converted = modernised
- small industrial units are being sited on the main roads including settlements
- farmers can make large amounts of money from reselling land to authorities or developers
- population decline means that cities miss out on local tax
less fund for local facilities
21
Q
what are the environmental effects of counter urbanisation?
A
- former Greenland sites are built on
- the spread of the rural urban fringe
- agricultural buildings are redeveloped at homes and businesses
22
Q
what are the 4 sectors of urban change?
A
urban resurgence: refers to the regeneration, both economic and structural, of an urban area which has suffered a period of decline. often been initiated by regeneration schemes but also due to wider social, economic and demographic processes
de-industrialisation: the reduction of industrial activity as capacity in the region. refers to the loss of jobs in the manufacturing sector.
de-centralisation: the movement of population and industry from the urban centre to outlying areas
encompasses both suburbanisation and counter urbanisation
rise of service economy
23
Q
what is urban resurgence?
A
the regeneration of an urban area resulting in an influx of population , typically young and highly mobile
24
Q
what are the main causes and effects of urban resurgence?
A
causes: deindustrialisation, suburbia, urban population, government incentives and public private partnerships
effects: converted warehouse accommodation, restaurants, bars and cafes
25
what are the main reasons of urban resurgence?
de-industrialisation in the second half of the 20th century
cities have revived their fortunes by developing strong financial centres
movement from the secondary sector into the tertiary sector
26
what were the social, economic and environmental effects of the london olympics (urban resurgence)
social:
- de-industrialised areas have been made into sociable areas
- shopping centres
- health and public services increased
economic:
- house prices increased
- renters kicked out due to BBC
- increased local economy
environment:
- toxic industrial waste released when dug up, however was cleaned up
27
what is urban form?
urban form is the physical characteristics of built up areas including shape, size, density and make up in settlements
conducted using a variety of scales from street level to an entire city
28
what causes urban form to change?
1. population
2. environment
3. economy
4. technology
5. policies
29
what is a world city?
a city that acts as a major centre for economic activity - finance, trade etc
serves not just the country its located in but the whole world
100 cities count for 30% of world's economy
global economy is channeled through knowledge, capital and expertise
increases the development gap, only functioning in certain locations
30
list some characteristics of a world city
variety of international financial services including insurance and real estate
centres of media and communications for global network
headquarters of multinational corporations
major manufacturing centres with post and container facilities
domination of the trade and economy of a large area
centre of new ideas and innovation
considerable decision making power at global level
high quality educational services and unis
multi-functional infrastructure offering some of the best legal, medicinal and entertainment facilities
31
what are the characteristics of a mega city?
1. environmental problems = increased levels of pollution - from increased cars, factories and high population density
health and waste concerns
2. residential differentiation = different socio-economic groups live further apart. housing shortages force poorest into inadequate housing
3. urban sprawl = expansion of the urban area, usually with insufficient infrastructure
4. edge cities = surrounded by new forms of retail, leisure and industrial etc
5. high density living = vertical resident zoning eg high rise developments
6. transit oriented development = urban areas develop around major road routes, bus routes
7. peripheral growth = development of new growth poles and dispersed settlements
8. car dominated = high use of cars led to low density housing estates on the edge of cities - leisure and retail centres created further out
9. redevelopment and conservation = protection of historic cores and redevelopment of former industrial sites
32
what are the physical factors affecting urban morphology?
topography = steep slopes or flat land
water = lakes and seas may limit growth
rivers may encourage development
dry points = areas locates away from flooding
natural resources eg coal
land type = swamps and wetland may limit growth
33
what are the human factors limiting urban morphology?
planning = urban expansion can be planned or unplanned
LICs = unplanned growth
government policies = focus of regeneration will result in gov ideologies
infrastructure = new developments are built along transport lines
land value, trading centres and conflict
34
what are the main land uses of a city?
out of town retreat:
spread out
low density
motorways
trials
resedential:
newer
driveways
gardens
CBD:
entertainment
services
high buildings
offices
shops
restaurants
inner city:
industrial
little green space
residential
green areas:
wood
park
protected green space
35
what is land value?
the peak land value intersection (PLVI) is the point with the highest land value and from here land prices decline - distance decay
usually only very profitable businesses can afford the high prices of the PLVI
36
describe the bid rent curve
the price and demand for real estate changes as the distance from the CBD increases
price of land closer to CBD is higher
different land uses will compete for desirable places of property in order to maximise profits
accessibly increases the potential for more customers
trade off between accessibility and cost of land
37
what are informal settlements?
shanty towns or favelas
commonly found in LICs
traditionally developed on the edge of cities and edge of transport routes
often located on undesirable on difficult building conditions eg steep slopes
38
describe the waugh model
outside: favelas
periferia
high cost housing
industry
CBD
39
what is the difference between HIC model and LIC models?
difference in HICs to LICs, wealth disparities
rapid rural to urban migration
poor infrastructure, build next to few existing roads
lack of regulation
squatter settlements
improvement over time while new arrivals to the city
industry re locating
lack of government policies
40
describe the burgess model
land values were the highest in the CBD and cities grow outwards in a series of concentric rings of land use
centre is the oldest and the newest part is on the outside
size and quantity increases from distance from the CBD
41
describe the hoyt model
modified the burgess model following the development of public transport
suggests that transport and physical features were important
industrial areas dropped outwards in sectors alongside main transport and housing growing up around there
42
what is the difference between the hoyt and burgess model?
concrete solid rings and one is more flexible with modified sectors
working class zones in hoyt
high class in burgess
topography and hills - suggest land does not change over time
urban resurgence and de-industrialisation is not taken into account
43
what is gentrification?
defined as the buying and renovating properties in more run down areas by wealthier individuals
44
why does gentrification happen?
1. rent gap = price of property has fallen below it's real value usually due to the lack of maintenance or investment
gap between actual and potential price
attracts people who renovate houses and sell for profit
2. commuting costs = commuting can be time consuming and expensive
moving close to the city centre, reduces the need to commute
3. pioneer image = trend of individuals moving into more edgy neighbourhoods
drawn to cultural living
4. support of gov and local decision makers = keen to improve economy and environment of inner cities
5. changing composition of households = seen the growth of single or two bed households without children
45
what are edge cities?
self contained settlements which have emerged beyond the original city boundaries, located close to transport links
people often commute
common in North America - a feature of post modern urban living
linked to urban sprawl
46
how do urban landscapes contribute to social segregation?
inner city becomes rundown and lacking in employment (de-industrialisation)
lower income groups stayed in the city centre where the wealthier middle class people moved out (suburbanisation)
social segregation is based on residential location
rise of the social (tertiary) industries are bought to the city centres and led to urban policy
intend to bring life back into the city
47
what are the features of town centre developments?
leisure = cinemas, theatres
space
street entertainment
night life
flagship attractions = national marine aquarium
new offices and conference centres
resedential development = redeveloping old buildings
48
what are cultural and heritage centres?
indépendant sellers, cultural places
eg jewellery quater, Birmingham
- diamond heaven vintage
- pasta de plaza
- 6,000 people living in floor to floor ceiling apartments
- linked to central Birmingham
49
what are fortress landscapes?
Landscapes designed around security, protection, surveillance
occurs in the uk
50
describe some features present in fortress landscapes
1. CCTV: Britain has also seen a boom in privately owned CCTV cameras which are now thought to outnumber, private surveillance cameras, 70 to 1
2. Street lights: unlit spaces can increase antisocial behaviour. street lights can deter homelessness from sleep as bright lights can disrupt sleep
bright lights can also increase feelings of safety and prevent crime. crime will move to other areas
3. anti-homeless measures: spikes and bumps on pavements and windows to prevent homelessness sleeping
handrails on benches also
4. defence mechanisms: speed bumps
railway and fencing amid mosquito alarms - high pitch sounds to deter people from lingering
51
how is crime prevented in fortress landscapes?
architects reduce the amount of crime by providing defensible space, high visibility policing and changing road layouts
defence mechanisms are controversial
52
what are gated communities?
often fenced off and exclusive communities
popular among USA + South Africa as they draw people interested in security and lifestyle benefits
high property prices with large outgoing costs and rules and regulations
properties increase in value
53
what are the features and characteristics of post modern western cities?
1. economy = dominated by quaternary and tertiary services, the city would be highly globalised and orientated towards consumption of goods
2. planning = stakeholders views incorporated into the decision making process and the city in spatial fragments rather then homogenised sectors for aesthetic reasons
3. culture and ethnicity = a highly polarised society that is highly fragmented and diverse - offering a dispora
4. urban structure = high tech corridors and post suburban developments such as edge cities. architecture and landscapes - there is a mix of different styles of buildings with different meanings plus historical references
5. government = services provided by the market rather than by public services, plus partnerships between public and private sectors
54
what is the difference of urban structure between modern and post-modern cities?
modern:
- homogenous functioning zoning
- dominant commercial centre
- steady decline in land value from centre
post-modern:
- chaotic multimodal structure
- highly specular centres
- large seas of poverty
- high tech corridors
- post suburban developments
55
what is the difference of urban government between modern and post-modern cities?
modern:
- managerial re-distribution of resources for social purposes
- public provision of essential services
post-modern:
- entrepreneurial use to lire mobile international capital and investment
-public and private sector working in partnership
- market provision of services
56
what is the difference of urban economy between modern and post-modern cities?
modern:
- industrial
- mass production
- economies of scale
- production based
post-modern:
- service sector based
- flexible production aimed at niche markets
- economies of scope
- globalised
- telecommunications based
- consumption orientated
57
what is the difference of urban planning between modern and post-modern cities?
modern:
- cities planned in totalry
- space shaped for social ends
post-modern:
- spatial fragments designed for aesthetic rather than social ends
58
what is the difference of urban culture/society between modern and post-modern cities?
modern:
- class divisions
- large degree of internal homogentry within class groups
post-modern:
- highly fragmented
- lifestyle divisions
- high degree of social polarisation
- groups distinguished by their consumption patterns
59
describe inequality
an unequal distribution of wealth
generally higher in LICs as they lack resources
to support the poorest citizens
60
describe cultural diversity
refers to the existence of a variety or ethnic groups within a society
can relate to nationality, race, age and traditions
migrants tend to move to cities because there are more jobs and less discrimination than coastal areas
61
why is there greater cultural diversity in cities?
cities tend to offer a greater range of employment opportunities
first point of entry for immigrants
cities tend to house earlier immigrant groups with the same ethnicity
established cultural diversity means there are specialist shops and religious centres
urban populations tend to be more tolerant of immigrants
62
what are the reasons for ethnic segregation in cities? (self segregation)
migrants seek the support and security of living near friends and relatives within in an ethnic minority
provision of specialist facilities such as places of worships
protection against racial abuse and attacks from majority of population
maintenance of culture and language
63
what are the reasons for ethnic segregation in cities?
traditionally, migrants have been a source of cheap labour forcing them to into areas of housing
ethnic minorities have been discriminated against in access to local housing authorities
as well as being less successful in securing mortgage loans
hostility from majority population
movement of the majority population out of the area = white flight
64
what are the issues associated with cultural diversity?
pressure on services
local authorities may need to provide bilingual literature and translations
english lessons may need to be provided
schools may need to alter their curriculum and change holidays to account for different ethnic groups
variations in academic attainment
65
what issues do economic inequalities bring?
political and social unrest - riots and protests
crime eg drug use
health problems
66
what are the social dimensions of sustainable cities?
* a community spirit is created
* people are always welcome to join in events
* neighbours look out for one another and respect each other
* all people are treated fairly
* there are low levels of crime, drugs and anti-social behaviour with viable, effective and community friendly policing
* adequate provision of schools and health services
* availability of food supplies
* green housing and buildings
* clean water and sanitation
* green public transport
* green energy access
* recreational areas and community support
67
what are the natural/environmental dimensions of sustainable cities?
actively seek to minimise climate change
* create cleaner, safer and greener neighbourhoods
* waste and recycling management
* energy efficiency
* water management
* air quality conservation
* adaption to and mitigation of climate change
* forest and soil management
68
what are the economic dimensions of sustainable cities?
local people have the opportunity to make money and have a good quality of life
* they are encouraged to open up small businesses and spend their wages locally to help improve other people’s businesses
* successful businesses create more jobs for or people, and better standards of living for more people in the community
* decent employment opportunities
* production and distribution of renewable energy
* investment in green technology and innovation
69
what are the economic dimensions of sustainable cities?
* when decisions are made about a community, local people are included in the decision-making process
* the community enjoys a sense of civic values, responsibility and pride
* adoption of green urban planning and design strategies
* strategies to reduce inequalities
* strengthening of civil and political rights
* support of local, national, regional and global links
70
what is the ecological footprint of urban areas?
cities tend to have a higher ecological footprint than rural areas
wealthier cities have a higher footprint than poorer ones
71
what is liveability?
the sum of the factors that add up to a communities quality of life (built and natural environments)
economic prosperity
social stability and equity
educational opportunity
cultural entertainment and recreation possibilities
72
what is liveability dependant on?
job opportunities
crime rates
open spaces
access to education
73
what are the features of a liveable city?
good provisions of schools and healthcare services
secure job and career opportunities to all residents
renewable energy
developing brownfield sites rather than greenfield sites
safe neighbourhoods
74
what is an urban heat island?
the zone around and above an area which has an high temperature than the surrounding rural areas
buildings and streets can interfere with airflow and pollution can play a part
75
describe the process of an urban heat island
1. paved surfaces and concrete crayons absorb the sun's rays and produce heat
2. chemicals emitted by cars, industrial facilities and even trees affect suns rays (trap and create more heat)
3. the warm air rising from a city may collide with most air from a nearby body of water
4. the warm air and precipitation can affect wind for miles
76
what are the causes of urban heat islands?
lower albedo = extensive dark surfaces absorb heat during the day and release it at night
large expanses of glass and steel reflect heat into surrounding areas
less vegetation = less evapotranspiration, moisture in the air is released
buildings leak heat from poor insulation in winter and air conditioning pumps hot air into the streets in the summer
rising heat, water vapour and condensation from air pollution provide the conditions necessary for precipitation and heavy more frequent thunderstorms
temperature decline from the urban centre to the rural fringe = thermal gradient
77
what are the strategies to reduce urban heat islands?
1. cool surfaces = cool roofs built from materials with high solar reflectance
store less solar energy so emit less heat
2. green roofs = plants and growing medium planted over a waterproof membrane
can reduce rooftop temperatures by 20-40 degrees
3. urban greening = planting vegetation and has a cooling effect
4. sky view factor = open space between buildings
5. cool cars = lighter coloured cars
78
Chicago and the urban heat island
1. vegetation = city hall used green roofs
£3,200 saved and law introduced that buildings with gov funding must be energy efficient and could contain green roofs
positive incentive as fast tracking of building permission
2. permeable pavements = allows water to pass and infiltrate through
3. green alleys = bike lanes, widen pavements
4. resurfacing with lighter colours
79
what are the urban heat island effects on precipitation?
rainfall can be higher over urban areas than rural areas - higher urban temps encourage the development of lower pressure over cities in relation to surrounding areas
convection and rainfall tends to be heavier and more frequent as does thunder and lightening
1. convection = ground surfaces are heated, rapid evapotranspiration takes place and result in cumulus cloud and convectional weather patterns
2. high buildings = induces air turbulence and promotes vertical motion
3. large amounts of water vapour from industrial sources
4. low pressure = caused by rising air and surface winds are drawn in from surround rural areas. air then converges as it is forced to rise over the urban canopy
5. prevailing wind = friction from the urban boundary creates an orographic process, air may split apart due to barriers created by high rise buildings and create clouds
6. city pollution can increase cloud formation and rainfall
pollutants act as hygroscopic (water attracting) nuclei and assist in formation
80
what are the urban heat island effects on fog?
fog increased along with industrialisation
early 1700s there would have been about 20 days every year but at the end of the 1800s this had risen to 50 days
average number of particles in city air is greater in urban areas than rural areas
particles as condensation nuclei and encourage fog formation at night
81
what are the urban heat island effects on thunderstorms?
develop in hot humid and are characterised by violent and heavy precipitation
chance of thunderstorms is increased, particularly during the late afternoon in the summer months
82
what are the urban heat island effects on wind?
urban structures have an effect on wind speed, direction and frequency
1. SA = uneven because of the varying height of the buildings which creates turbulence giving rapid and abrupt changes to wind direction and speed
2. high rise buildings cause slow air movement but they also channel air into canyons between them
3. convectional processes = calm and clear nights draw in strong localised winds from cooler areas
83
what is urban air quality?
particulates are fine particles - about 80% in urban areas are from vehicle exhausts
burning of refuse products fine eg sulphates
constitution and mining produce particulates
plants and mould also generate particulates in form of spores
84
what are the sources and impacts of urban air quality?
sources:
cars and high volumes of traffics
impacts:
can lead to serious health issues and even death
locations like schools and parks are next to busy roads
85
describe nitrogen dioxide
at high concentrations, NO2 can inflame the airways and long term exposure can affect lung functioning and breathing
can worsen asthma
5,900 premature deaths across London associated with NO2 long term exposure
sources:
- road transport - responsible for 50% emitted
- urban areas and busy roads
86
describe nitrogen oxides
contributes to respiratory diseases, formation of ground-level ozone and acid rain
associated with impaired lung function and worsening of asthma, COPD and CVD
70% originates from road transport
large areas exceed recommended safe limits
emitted by cars, power plants etc
87
describe PM25
fine particulate matter of 2.5 micrometers or less in diameter
penetrates lung barrier and enters the blood system causing CVD and COPD
38% from burning wood and coal in domestic fires
12% from road transport
13% from solvent use and industrial process
16% industrial combustion
88
what causes water pollution?
industrial discharges
mobile sources
resential wastewater and sewage
trash
polluted stormwater runoff
89
what are the impacts of water pollution?
over 1.2 million people lack access to clean water
water born infections make up 80% of all infectious diseases wide world
heavy metals from industrial processes lead to birth defects
- raw sewage can lead to cholera and typhoid
algae levels increase in polluted water which leads to the suffocation of aquatic species due to a lack of oxygen
90
what are the main reasons for dereliction?
out-migration
decline in housing quality
impact from past urban planning decisions
loss of industry
deindustrialisation
suburbanisation
crime and vandalism
91
what are the strategies of dereliction
1. regeneration schemes
2. land remediation = removal of pollution
3. community action
92
describe the drainage basin in urban areas
urban areas have 5-15% more precipitate than rural areas
however there is less vegetation and therefore evapotranspiration reduces moisture in the air
less interception and more precipitation landing on hard impermeable surfaces
drains are needed to shift all the surface water to prevent flooding
93
what is a culvert?
structure that allows water to flow under a road, railroad from one side to the other side
typically embedded so surrounded by soil
may be made from pipe, reinforced concrete or other material
94
what is canalisation?
when rivers are straightened and deepened
run off piped into rivers in an attempt to manage excess water
95
why are urban areas more at risk from flooding?
higher risk of precipitation, urban heat island etc
water will flow more rapidly along pavements and road surfaces
run off increases
drains may be unable to cope with the sheer volume of water and culverts may become blocked with debris
lower levels of vegetation, interception reduced
96
describe flood hydrographs
they record and measure the relationship between discharge and precipitation
overland flow = volume of water reaching the river from surface runoff
through flow = volume of water reaching through the soil and underlying rock layers
97
what are some hard engineering drainage management techniques?
1. river straightening
+ increases velocity
- city may have already been built around river
- expensive
- more problems downstairs
2. artificial levees
+ increases amount of volume
- unattractive
98
what are some soft engineering drainage management techniques?
1. afforestation
+ delays and increases lag time
+ good for environment, increases ecosystems
- not enough land
- takes time to grow
- not practical
2. flood plain zoning
+ can put areas of less importance by rivers
- city may have already been built up around the river
99
what are SUDS?
sustainable urban drainage systems are drainage solutions that provide an alternative to the direct channeling of surface water through networks of pipes and sewages to nearby watercourses
100
How do SUDS prevent flooding?
By mimicking natural drainage regimes, SUDS aim to reduce surface water flooding, improve water quality and enhance the amenity and biodiversity value of the environment.
SUDS achieve this by lowering flow rates, increasing water storage sapacity and reducing the transport of pollution to the water environment.
101
list SUD techniques
* Swales - wide, shallow drainage channels that are normally dry
* Permeable roads and pavements - porous paving and concrete
* Infiltration trenches - gravel filled drains
* Bioretention basins - gravel filled or sand filled filtration layers beneath reed beds and other wetland habitats to collect, store and filter dirty water
* Detention habitats - excavated basins to act as holding ponds for water storage
* Rain-gardens - shallow landscaped depressions with flowers and shrubs (allows some water storage)
* Green roofs - minimises run off from building roofs
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what are the benefits of SUDS?
slow down runoff and reduce risk of flooding
reduce the risk of sewer flooding during heavy rain
prevent groundwater supplies
provide valuable habitats
creates green spaces
