Urbanisation Processes

I will discuss this according to the Urban Process Timeline, so that it is orderly. The timeline is as follows:

1. Agglomeration
2. Suburbanisation
3. Commuting
4. Urban regeneration
5. Counter-urbanisation
6. Urban re-imaging
7. Urbanisation of suburbs

Urbanisation: Process of change that converts rural areas, regions and countries into urban ones. It is also the growth of towns and cities which leads to an increasing percentage of a country's population living in urban settlements. 

1. Agglomeration: This is how urban settlements first appear. It is the concentration of people and economic activities at favourable locations. E.g. at river crossing points so there is a supply of water, near a mineral resource such as coal, iron or oil. Long ago, defence was important so people were able to protect themselves. E.g. hilltops made good defensive sites, there were good views but it was hard to reach, and would not be sheltered from strong winds. 

2. Suburbanisation: Definition: The outward spread of the urban area, often at lower densities compared with the older parts of a town or city. 

• As towns grow, they expand outwards through suburbanisation. 
• Adds to built-up area, but building densities lower than in older parts of town. 

3. Commuting: People start to move out of the town/city to live in smaller more rural areas. These are often called dormitory settlements because many new residents only sleep there. They commute to work and still make use of urban service like shops and hospitals. Commuting definition: Travel some distance between one's home and place of work on a regular basis. 

4. Urban regeneration: involves re-using areas in old parts of the city where businesses and people have moved out into the suburbs or beyond. (Expanded upon in another post 'Urban regeneration and re-imaging)

5. Counter-urbanisation: the movement of people and businesses (employment) from major cities to smaller towns/cities and rural areas. 

6. Urban re-imaging: changing the image and look of an area to attract people.  (Expanded upon in another post 'Urban regeneration and re-imaging)

7. Urbanisation of suburbs: suburbs are generally areas of low-density development, so instead of using rural areas governments want to use suburban areas--suburban areas become more dense, raised to an urban level--. Empty spaces are being developed and large detached houses are replaced by flats. The suburbs are no longer just residential areas anymore, shops and other services start to locate there too.

If you need further details/clarification, just comment and let me know. :)

Urban regeneration and re-imaging

Urban regeneration + urban re-imaging= rebranding-->to help sell an urban area to a new target market

Urban regeneration and Urban re-imaging are different. 
Definitions:
Urban regeneration: the investment of capital in the revival of old, urban areas by either improving what is there or clearing it away and rebuilding.


Urban re-imaging: changing the image of an urban area and the way people view it. 

Urban regeneration:  Over time, old parts of town would suffer decline. The factories would move elsewhere, resulting in jobs lost. Quality of life and housing is poor, so the place needs to be regenerated, as in 'brought back to life'. Regeneration includes:

• transforming the economy of the area by encouraging new businesses to replace those that have closed/moved elsewhere. Employers--people who might provide employment in the area by using/buying shops or offices need to be brought in to the scheme as they can provide new work which hopefully improves the economy. 
• upgrade the quality of the built environment by a) finding new uses for old and often empty buildings, b) clearing them away to make way for new ones. (The London Docklands is a good case study which I have talked about in another post. The old warehouses in the run-down dockland area were converted into luxury apartments and flats which also transformed its image.)

Urban re-imaging: To change the reputation of a city or an area by: 

• focusing on a new identity/function--Docklands had more services such as pubs and cinemas so it became the new 'cool' place to be. 
• changing the quality and appearance of the built-up area--Docklands was completely redeveloped and regenerated, new industries would locate there so there were more jobs and it was a good brownfield site development, re-using space and saving land in the process (reclaiming land and putting it to another use) 

Shanty Towns

Shanty town (aka. squatter settlement) is a slum settlement (sometimes illegal or unauthorised) of impoverished people who live in improvised dwellings made of scrap materials such as packing boxes, wooden planks, corrugated iron and plastic sheeting.

Why are they formed? Where are they found? 
When people from poor rural areas migrate to LIC cities they find that there are no houses for them, so they have to build homes on land available to them. The land is usually in areas of no economic value, on the edge of town, along main roads or on steep slopes. They often build on land they do not own, or on land that they do not have permission to build on.

Many areas on which shanty towns are built are unsafe:

• prone to flooding
• prone to landslides (steep slopes--this is why it is unoccupied, people cannot build tall buildings on steep slopes..)
• heavily polluted location

Often, they lack basic services such as electricity, water and sewerage. (Sewerage: the provision of drainage by sewers) Sometimes raw sewage runs across the streets and contaminates the area, leading to a wide variety of diseases. It is an unhealthy place to live in. However, for many people living in a shanty town is better than the life they had in rural areas. They prefer to live there and work in the informal economy, as it offers greater opportunities.  

Case study of inner city redevelopment: London Docklands

You can refer to page 168-169 of Key Geography for GCSE textbook.

During 19th Century-port of London busiest in the world
Surrounding the docks were:

• many industries using imported goods
• high-density, poor quality housing (typical old inner-city area)

1950s-ships become bigger = unable to reach London's docks

By 1970s, area became derelict, with few jobs, few services and poor living conditions. 

Many people forced to leave area to look for work + better quality of life.

Because: 

• traditional jobs in docks were lost (manual, unskilled, unreliable and poorly paid)
• most housing was substandard-lacking basic amenities (services e.g. water, sewerage, electricity..) and located in poor-quality environment

When textbooks talk about amenities, they mean:

Amenities definition: A desirable or useful feature/facility of a building/place. e.g. basic services in housing like electricity, water, sewerage... 

In 1981, the London Docklands Development Corporation (LDDC) was set up to try to improve:

• social
• environmental
• and economic conditions of the area

LDDC given 3 main tasks: 

1. Improve social conditions by:

• creating new housing
• creating new recreational facilities
• improving shopping facilities

2. Improve economic conditions by:

• creating new jobs
• improving transport system (to and within area)

3. Improve environmental conditions by: 

• reclaiming derelict land 
• cleaning up docks
• planting trees
• creating areas of open space (people like parks and peaceful green surroundings)

To clarify if you're confused: 

Derelict land: land that is damaged or abandoned and cannot be put to use until damage is repaired 

Reclaiming derelict land is: to recover land that has lost its productivity and to make it usable again

What improvements were made after 1981?

Social Improvements


1. Housing

• 22,000 new homes created (many are former warehouses converted to luxury flats)
• 10,000 refurbished former terraced houses (Refurbish: to renovate and redecorate smth esp. a building

-In 1981 population= 40,000

-In 2000 population= 85,000

2. Services

• several huge new shopping malls
• post-16 college and campus for new University of East London
• leisure facilities: watersports marina, national indoor sports centre 

Economic Improvements


1. Employment

• number of jobs increased, In 1981= 27,000  In 2000= 90,000
• many new firms and financial institutions e.g. Stock Exchange, ITV Studios, newspaper offices
• many high-rise office blocks, esp. at Canary Wharf

2. Transport

• Docklands Light Railway links area with central London
• Jubilee Line Underground extension
• City Airport
• Many new roads, including M11 link 

Environmental Improvements

• 750 hectares of derelict land reclaimed 
• 200,000 trees planted
• 130 hectares of open space created

However, remember that not everyone was happy about the changes, because not everybody benefited:


Negative effects on the local people: (in descending order of importance to me, others may be more important for you, but structure your answers in an exam so that you write what's most important first!)

• new jobs went to people living outside the area, as local people did not have the technical skills (a lot of new jobs created were in finance/media industries--using high tech equipment--local people not skilled enough to do these types of jobs)
• a lot of new housing far too expensive for locals
• more money was spent on providing infrastructure (expensive offices + houses) and a clean environment for office workers; than on services (e.g. hospitals and care for elderly, health + educational facilities for local people)
• noise + air pollution (dust) from the building
• prices in area generally increased (e.g. in shops, bars etc.) --newcomers were wealthy, causing local shop and recreational prices to rise--
• newcomers did not mix with local people--tension--causing a breakdown of East Ender's community

Greenfield vs Brownfield

Basically a cut down version of pg 165 of Edexcel IGCSE Geography textbook

Some people aren't happy that the countryside around towns and cities of HICs is being developed and lost.
Environmentalists believe that new developments should be done on brownfield sites opposed to greenfield sites.


Brownfield site: land that has been previously used, abandoned, and now awaits a new use
Greenfield site: land that has not been used for urban development

Brownfield site

Advantages: 

• reduces loss of countryside and land that could have agricultural/recreational use
• revives old and disused urban areas
• services already installed e.g. water, electricity, gas and sewerage
• nearer to main areas of employment=reduces commuting

Disadvantages:

• more expensive as old buildings must be cleared and land decontaminated (clear pollution)
• often surrounded by rundown areas so is not appealing as residential location, especially to wealthy people
• higher levels of pollution=less healthy
• may not have good access to modern roads

Greenfield site

Advantages: 

• cheaper and rates of house building faster (no need to clear old buildings/pollution)
• layout not hampered by previous development, can be made efficient + pleasant easily
• healthier environment

Disadvantages:

• valuable farm/recreational space lost
• attractive scenery lost
• loss of wildlife and their habitats
• noise + light pollution due to development
• encourages suburban sprawl

No clear winner between the two. All depends on:

• what land use? Housing-quite flexible in terms of where it can be built, but shops/offices/industries need specific locations (e.g. close to main road so workers can access office easily)
• circumstances of particular town/city. Green space-valuable? Reusing brown space-serious problems? High costs?
• your own set of values. Should countryside be protected? Should it be released for urban growth? 

What is Urbanisation?

Urbanisation is happening fastest in poorer countries

Urbanisation is the growth in the percentage of a country's population living in urban areas. It's happening in countries all over the world-more than 50% of the world's population currently live in urban areas (3.4 billion ppl) and this is increasing everyday. But urbanisation differs between richer and poorer countries. 

1. most of the population in richer countries already live in urban areas. e.g. more than 80% of the UK's population live in urban areas
2. not many of the population in poorer countries currently live in urban areas e.g. around 25% of the population of Bangladesh live in urban areas.
3. most urbanisation that's happening in the world today is going on in poorer countries and it's happening at a fast rate

Urbanisation is caused by rural-urban migration

Rural-urban migration is the movement of people from the countryside to the cities. 

This causes urbanisation in richer and poorer countries.

The reasons why people move are different in poorer and richer countries though.

Reasons why people in poorer countries move from rural areas to cities:

1. there's often a shortage of services (e.g. education, access to water and electricity) in rural areas. Also ppl from rural areas sometimes believe that the standard of living is better in cities. (even though this often turns out not to be the case)
2. there are more jobs in urban areas. Industry is attracted to cities because there's a larger workforce and better infrastructure than in rural areas.
3. In rural areas some people are subsistence farmers. This means they grow food to feed their own family and sell any extra to make a small income. Poor harvests and crop failures can mean they make no income and even risk starvation.

Reasons why people in richer countries move from rural areas to cities: 

1. most urbanisation in rich countries occurred during the Industrial and the Agricultural Revolutions (18th and 19th centuries)-machinery began to replace farm labour in rural areas, and jobs were created in new factories in urban areas. People moved from farms to towns for work. 
2. in the late 20th century, people left run-down inner city areas and moved to the country. But people are now being encouraged back by the redevelopment of these areas.

Good healthcare and high birth rate in cities

It's normally young people that move to cities to find work. These people have children in the cities, which is what is meant by 'natural increase in population'.. fancy terms. So this increases the proportion of the population living in urban areas. Also, better healthcare in urban areas means people live longer, again increasing the proportion of people in urban areas. 

Fragile Environments Keywords

Agro-forestry: the growing of trees for the benefit of agriculture: as wind breaks or as protection against soil erosion

Alternative energy: renewable sources of energy, such as solar and wind power, that offer an alternative to the use of fossil fuels

Chlorofluorocarbons (CFCs): chemicals once used in foams, refrigerators, aerosols and air-conditioning units. Their use is now banned because they were thought to be responsible for the destruction of the world’s ozone layer and for part of the greenhouse effect

Climate change: long-term changes in the global atmospheric conditions

Deforestation: the deliberate clearing of forested land, often causing serious environmental problems such as soil erosion

Desertification: the spread of desert conditions into what where semi-arid areas

Famine: a chronic shortage of food resulting in many people dying from starvation

Fossil fuel: carbon fuels such as coal, oil and natural gas that cannot be ‘remade’ because it will take tens of millions of years for them to form again (i.e they are finite)

Fragile: a term used to describe those natural environments that are sensitive to, and easily abused by human activities

Global warming: a process whereby global temperatures rise over time

Malnutrition: a condition resulting when a person is unable to eat what is needed to maintain good health

Overgrazing: when pasture or grazing is unable to support the number of animals relying on it for food. The result is the vegetation cover declines and soil erosion sets in.

Population pressure: when the number of people in an area begins to approach carrying capacity and places a strain on available resources

Refugee: a person whose reasons for migrating are due to fear of persecution or death

Soil erosion: the washing or blowing away of topsoil so that the fertility of the remaining soil is greatly reduced

Sustainable: a term used to describe actions that minimize negative impacts on the environment and promote human well-being

Well-being: a condition experienced by people and greatly influenced by the standard of living and quality of life 

Urban Environments Keywords

Accessibility: the ease with which one location can be reached from another; the degree to which people are able to obtain goods and services, such as housing and healthcare

Brownfield site: land that has been previously used, abandoned and now awaits a new use

Congestion: acute overcrowding caused by high densities of traffic, business and people

Counterurbanisation: the movement of people and employment from major cities to smaller cities and towns as well as to rural areas

Environmental quality: the degree to which an area is free from air, water, noise and visual pollution

Ethnic group: a group of people united by a common characteristic such as race, language or religion

Greenfield site: land that has not been used for urban development

Land value: the market price of a piece of land; what people or businesses are prepared to pay for owning and occupying it

Megacity: a city or urban area with a population larger than 10 million

Poverty: where people are seriously lacking in terms of income, food, housing, basic services (clean water and sewage disposal) and access to education and healthcare. See also Social Deprivation.

Shanty town: an area of slum housing built of salvaged materials and located either on the city edge or within the city on hazardous ground previously avoided by urban development; I like to think of it as: a slum settlement (sometimes illegal or unauthorized) of impoverished people who live in improvised dwellings made from scrap materials: packing boxes, corrugated iron and plastic sheeting, often on undesirable locations such as steep slopes or on the city edge.

Social deprivation: when the well-being and quality of life of people falls below a minimum level

Social segregation: the clustering together of people with similar characteristics (class, ethnicity, wealth) into separate residential areas

Socio-economic group: a group of people sharing the same characteristics such as income level, type of employment and class

Squatter community: see Shanty town

Suburbanisation: the outward spread of the urban area, often at lower densities compared with the older parts of the city or town

Urban regeneration: the investment of capital in the reviving of old, urban areas by either improving what is there or clearing it away and rebuilding

Urban re-imaging: changing the image of an urban area and the way people view it

Urban managers: people who make important decisions affecting urban areas, such as planners, politicians and developers

Urbanisation: growth in the percentage of people living and working in urban areas

Hazardous Environments Keywords

Adjustment: changes designed to react to and cope with a situation, such as the threat posed by a hazard

Earthquake: a violent shaking of the Earth’s crust

Emergency aid: help in the form of food, medical care and temporary housing provided 

immediately after a natural disaster

Epicentre: the point on the Earth’s surface that is directly above the focus of an earthquake

Hazard: an event which threatens the wellbeing of people and their property

Infrastructure: the transport networks and the water, sewage and communication systems that are vital to people and their settlements and businesses

Lahar: a flow of wet material down the side of a volcano’s ash cone which can become a serious hazard

Natural disaster: a natural event or hazard causing damage and destruction to property, as well as personal injuries and death

Natural event: something happening in the physical environment, such as a storm, volcanic eruption or earthquake

Plate movement: mainly the coming together and the moving apart of tectonic plates

Prediction: forecasting future events or changes

Pyroclastic flow: a devastating eruption of extremely hot gas, ash and rocks during a period of explosive volcanic activity; the downslope flow to this mixture is capable of reaching speeds up to 200kph.

Risk assessment: judging the degree of damage and destruction that an area might experience as a result of a natural event

Storm surge: a rapid rise in sea level in which water is piled up against the coastline to a level far exceeding the normal. It tend to happen when there is very low atmospheric pressure and where seawater is pushed into a narrow channel

Subduction: the pushing down of one tectonic plate under another at a collision plate margin. Pressure and heat convert the plate into magma

Tropical revolving storm: a weather system of very low-pressure formed over tropical seas and involving strong winds and heavy rainfall (also known as cyclone, hurricane or typhoon)

Tsunami: a tidal wave caused by the shock waves originating from a submarine earthquake or volcanic eruption

Volcanic activity: the eruption of molten rock, ash or gases from a volcano

Economic Activity and Energy Keywords

Economic sector: a major division of the economy based on the type of economic activity. The economies of all countries are made up of three sectors; most HICs have a fourth sector.

Energy: heat and motive power. The former provided by the sun and by burning coal, oil and timber, the latter provided by electricity, gas, steam and nuclear power

Energy consumption: the amount of energy used by individuals, groups of countries

Energy efficiency: making the most of energy sources in order to cut down on waste and reduce consumption

Energy gap: a gap created because the loss of energy caused by phasing out the use of fossil fuels is greater than the amount of energy that is being developed from new, low-carbon sources

Fossil fuel: carbon fuels such as coal, oil and natural gas that cannot be ‘remade/renewed’, because it will take tens of millions of years for them to form again

Global shift: the movement of manufacturing from HICs to cheaper production locations in LICs

High-tech industry: economic activities that rely on advanced scientific research and produce new, innovative and technologically advanced products, such as microchips, new medical drugs and new materials

Informal employment: types of work that are not officially recognized and are taken up by people working for themselves on the streets of LIC cities. e.g. shoe shining, selling stuff on the street

Non-renewable energy: energy produced from resources that cannot be replaced once they are used. Examples include the fossil fuels of coal, oil and natural gas

Primary sector: economic activities concerned with the working of natural resources-agriculture, fishing, mining and quarrying

Quaternary sector: economic activities that provide highly skilled services such as collecting and processing information, research and development

Secondary sector: economic activities concerned with making things, such as cars, buildings and electricity

Renewable energy: sources of energy which cannot be exhausted, such as the sun, wind and running water

Tertiary sector: activities that provide a wide range of services and enable goods to be traded

Transnational company (TNC): a large company operating in a number of countries and often involved in a variety of economic activities

River Environments Keywords

Abstraction: the taking of water from rivers, lakes and from below the watertable (aquifers)

Attrition: A process of erosion. The material is moved along the bed of a river, collides with other material, and breaks up into smaller pieces. 

Aquifers: permeable rock that can transfer or store water below ground (ground water)

Base flow: the usual level of a river, the part of a river's discharge fed by groundwater

Catchment area=Drainage basin

Channel network: the pattern of linked streams and rivers within a drainage basin

Clean water: water that is fit for human consumption and is therefore relatively free from pollutants

Condensation: when water vapour is cooled and changes state to form water droplets

Confluence: where two rivers/streams meet

Corrasion: a process of erosion, sometimes known as abrasion. This is when fine material rubs against the river bank. The bank is worn away, by a sand-papering action called abrasion, and collapses. 

Corrosion: a process of erosion. Some rocks forming the banks and bed of a river are dissolved by acids in the water

Cumecs: cubic metres per second, the unit for river discharge

Dam: a large structure, usually of concrete, sometimes earth, built across a river to hold back a large body of water (reservoir) taken for human use

Deposition: the dropping of material that was being carried by a moving force, such as running water

Discharge: the quantity of water flowing in a river channel at a particular location and time

Drainage basin: It is a water system involving external inputs and outputs, where the amount of water in the system varies over time. It is the area where water from precipitation (rain/snow..) drains downhill into a common body of water such as a river or lake. [The area drained by a river and its tributaries.]

Erosion: the wearing away and removal of material by a moving force, such as running water

Flood plain: the flat land lying either side of a river which periodically floods

Hydraulic action: a process of erosion. The sheer force of water hitting the banks of a river

Hydrograph: a graph showing the discharge of a river over a given period of time

Hydrological cycle: the global movement of water between the air, land and sea

Impermeable: if a material is impermeable, it does not allow water to pass through it

Interlocking spur: a series of ridges projecting out on alternate sides of a valley and around which a river winds

Levee: a raised bank of material deposited by a river during periods of flooding

Mass movement: the movement of weathered material down a slope due the force of gravity

Meander: a winding curve in a river's course

Oxbow: a horseshoe-shaped lake once part of a meandering river, but now cut off from it

Pollution: the presence of chemicals, dirt or other substances which have harmful or poisonous effects on aspects of the environment such as rivers and the air

Reservoir: an area where water is collected and stored for human use

River regime: the seasonal variations in the discharge of a river

Saltation: a process of transportation. smaller stones are bounced along the bed of a river in a leap-frogging motion

Solution: a process of transportation. Dissolved material is transported by the river.

Suspension: a process of transportation. Fine material, light enough in weight to be carried by the river. It is this material that discolours the water.

Stores: features, such as lakes, rivers and aquifers, that receive, hold and release water

Stormflow: the increase in stream velocity caused by a period of intense rainfall

Stream velocity: the speed at which water is flowing in a river at a given location and time

Traction: a process of transportation. Large rocks and boulders are rolled along the bed of the river

Transfers: the movement of water between stores in the hydrological cycle

Transport: the movement of a river’s load

Waterfall: where a river’s water falls vertically, as where a band of hard rock runs across the river channel

Watershed: the boundary between neighbouring drainage basins

Weathering: the breakdown and decay of rock by natural processes, without the involvement of any moving force

Mississippi Flood Defence Scheme Case Study

An example of an exam question, and how to structure your answer because there is a lot of information. This is very full on and very long, in an exam, you may want to cut short your answer. But this has everything, is very detailed, so that you have an example of a complete answer. Make it your own words and make it more concise. That's your job now!

For a named flood defence scheme, describe and explain how it helps to reduce the flood risk. (9m)

Name of flood defence scheme: Mississippi River Flood Defence Scheme, USA

The Missouri River is a main tributary to the Mississippi River, 6 huge dams have been built on it, creating a 1600km chain of 105 reservoirs, controlling the amount of water added to the Mississippi River. Thus reducing the risk of flooding. The Tennessee is another major tributary, 9 dams have been built on its river such as Kentucky and Nick-a-Jack, and 10 have been built on its tributaries. The Tennessee Valley authorities (TVA) have also been responsbile for planting many trees. Afforestation has occurred in the upper Mississippi drainage basin system, delaying surface run-off by interception by vegetation. Trees also absorb water, their roots delay throughflow and run-off too. All this reduces the amount of water reaching the river and delays it as well. This gives the Mississippi more time to transport flood water away. The Bonnet Carré floodway has been constructed to divert excess water from the Mississippi. It begins 50km North of New Orleans and diverts excess water along a 9km spillway through 350 small bays to Lake Pontchartrain, and eventually into the Gulf of Mexico. The Mississippi River has been straightened and shortened. From 1934-1945, a 530km stretch of river has been shortened by almost 300km. It cuts through the meanders making it straighter and shorter. this increases the gradient and therefore the speed, so flood water can be transported away faster. Levées have been strengthened and heightened. Instead of soil covered by bundles of willow, which is very vulnerable to erosion, it is now reinforced concrete. A special barge backs away from the shore leaving 25m x 8m concrete mattresses. This is repeated until the deepest part of the bank is covered to above flood level. For example in St. Louis where the confluence of the Missouri and the Mississippi is, it has a levée made of reinforced concrete. It is 15.8m high. The flood level of 1993 was 15.05m. This levée protects St. Louis from the Mississippi flooding. 

An update:

To help you formulate your own answer, I thought this might help:

River management/Flood Defence scheme: Mississippi, USA (reduced flood risk)

1. Dams and reservoirs

The Missouri River (tributary): 

• 6 huge dams built on it,
• creating 1600km chain of 
• 105 reservoirs that prevent flooding, provide water supply, and HEP.

-these dams reduce water reaching/added to the Mississippi, without them, 1993 flood would be even worse.

1b. Dams and reservoirs 2

The Tennessee River (tributary): 

• Tennessee Valley Authorities (TVA) set up in 1930s have many functions, one of which is to control flooding of this river. 
• 9 reservoirs on the main river (e.g. Kentucky, Nick-a-Jack, Wilson, Wheeler..)
• 10 reservoirs on its tributariers

Dams hold back water in times of flood, and release it when river levels are lower. 

Success-1957, instead of river reaching dangerous peak of 16.5m, dams and reservoirs limited the level to harmless 9.8m. 

Note: The TVA is a multipurpose scheme which:

• controls flooding
• provides a water supply
• produces hydro-electricity
• improves navigation
• increases afforestation
• reduces soil erosion
• encourages industry
• encourages tourism

2. Afforestation 

TVA also responsible for planting many trees. Trees delay run-off and reduce amount of water reaching the river, as its roots absorb some. 

3. Diversionary Spillways

These are overflow channels-they take surplus water during times of flood.

The Bonnet Carré Floodway begins 50km north of New Orleans.

In times of flood, it diverts excess water away from the Mississippi through a 9km long spillway, through 350 small bays/reservoirs into Lake Pontchartrain, where the water eventually ends up in the Gulf of Mexico.

This has greatly reduced flood risk in New Orleans and Baton Rouge. 

4. Straightening and shortening course

By cutting through narrow necks of several large meanders. 

Between 1934 and 1945, a 530km stretch of river was shortened by almost 300km. 

By decreasing the distance, the gradient increases, hence the speed increases--so flood water is transported away quicker. 

5. Strengthening the levées

Levées used to be made of soil covered by bundles of willow-but this was prone to erosion.

Now, specially designed barges back away from shore laying concrete mattresses measuring 25m x 8m. The process is repeated until the bank is covered from the deepest point of the river to above the flood level. 

St. Louis levée is made of reinforced concrete (steel bars inside) 15.8m high (and 18km long) and protects St. Louis, because that is where the confluence of the Missouri and the Mississippi is. (1993 flood peak was 15.05m, but the levée withstood the water's weight.)

River Environments (Q&A)

Please note that these are my own answers and my own words. They may not be entirely perfect, so please comment and help to make this better. Please please do not plagiarise, I would not be blogging and trying to help if I didn't trust people to only use this to help them revise etc. I would love comments asking for help and specific topics you would like posted about, as that makes my life easier. So I can focus on one topic. Check out my other blogs for the other subjects too. All my gcse blog urls go like this: askmichelle*subject*.blogspot.com
Thank you! Hope this helps! )


What is the difference between throughflow and groundwater flow? (2m)
Ans: Throughflow is water flowing through the soil whilst groundwater flow is water flowing through permeable rocks and reaching the river. Groundwater flow is slower.

Describe the transfer of water through a drainage basin. Start with the input of water as precipitation. (3m)
Ans: Precipitation occurs in the form of rain, snow, sleet or hail. If it is rain, some is intercepted by vegetation. It will fall slowly to the ground as dripflow. Some is surface storage, some reaches the river by surface run-off. Some infiltrates and is held as soil moisture. It may go as throughflow or percolate to the groundwater storage and reach the river as groundwater flow.

Explain the main physical causes of river flooding. (2m)
Ans: The type and amount of precipitation in a drainage basin system is one factor. If it rains heavily for a long period of time, the soil and rock will be saturated-provided it is permeable. Thus surface run-off will increase, increasing flood risk as well. Severe thunderstorms cause rapid surface run-off and flash floods. If the underlying soil and rock is impermeable, infiltration can't occur. Thus increasing flood risk as surface run-off is fast.

Suggest how human activities in a drainage basin can help to cause flooding. (3m)
Ans: If it is an urban area, there will be impermeable surfaces such as tarmac and concrete. This prevents infiltration and increases surface run-off. Storm drains transport water to the river faster than surface run-off, increasing the river's level and flood risk. The land use of the drainage basin system is important. If it is deforested, there will be more surface run-off, and there will be no interception by vegetation. Thus water will reach the river quicker, increasing risk of flooding.

For a named dam or reservoir project, describe how it is a multi-purpose scheme. 
Name of dam or reservoir project: Three Gorges Dam, Yangtze River, China.
Ans: The Three Gorges Dam is a multi-purpose scheme because it has many uses. It firstly prevents flooding downstream, it also generates HEP-Hydro electrical power, about 8% of China's energy. It creates jobs and improves river transport upstream. China can then transport 10,000 ton vessels 2,000km inland to Chongqing. It also provides water supply for surrounding areas. The dam may be a tourist attraction, tourism brings in money and creates jobs.

River Environments-Fieldwork

Describe how you would measure the velocity of the river flow? (4m)

Equipment needed:

• clipboard with paper and pen, and drawn table to record results 
• 2 ranging poles
• a measuring tape
• a flowmetre with a datalogger

By using a measuring tape between 2 ranging poles on either side of the riverbank to get the width, and dividing the width into 6, you can measure the velocity at 5 equal spaces in the river. A person can stand with a flowmetre in the river, with the flowmetre's impellor facing the water flow so that their body does not block the river flow and disrupt results. The impellor is turned by the water and data is recorded on the datalogger. By taking the average of the 5 readings, accuracy is achieved and you can get the velocity of the river flow.

Describe the fieldwork techniques you would use to collect data about a river's discharge.  (6m)

River's discharge= cross sectional area x velocity of the river (cumecs-cubic metres per second)

Cross sectional area can be calculated by multiplying the average depth of the river by its width. To get the width, 2 people hold a ranging pole each on each end of the river bank-on the edge. Connect a measuring tape across it and record the width, easier if the '0' mark is on one end of the bank. Calculate depth by dividing the width by 11, and measuring depth at each regular interval of the width. Should have 10 sites to collect data from. At each of the 10 sites, a person stands in the river channel with a metre ruler resting gently on the river bed with the '0' mark on the river bed. It's better if the ruler is sideways on the river flow so water flows around it-making the measurement more accurate. Calculate the average of the 10 measurements, multiplying this average depth by the width to get cross sectional area. To get velocity, divide width by 6. Collect data from 5 sites in the river channel in regular intervals of the width. A person should hold a flowmetre with an impellor and a datalogger attached to it. The person should stand behind flowmetre with impellor facing the river current. Record velocity reading from datalogger. Calculate the mean of the readings from all 5 sites and multiply this by cross sectional area to get river discharge.