geography fragile environments

what is river flooding?

when there is high river discharge and the bank full capacity of the river channel is exceeded causing it to over spill its banks after a rainfall event

what is bank full capacity?

the maximum river discharge that a particular river channel is capable of carrying without flooding

what is risk assessment?

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

what are soft engineering strategies?

natural materials that restore the river's natural state or reduce the damage caused by flooding

what are hard engineering strategies?

man-made artificial structures that change the shape of the river or control the flow of water

how does relief cause flooding?

steep slopes cause rapid run off

how does snow melt cause flooding?

when there are sudden increases in temperature it causes snow to melt rapidly which increase river discharge entering the river by OF because the ground is impeded

how does vegetation cause flooding?

decrease in vegetation especially trees decreases interception which increases OF

how does deforestation cause flooding?

less trees means less interception which increase the speed of water entering the river

how does urbanisation cause flooding?

increase impermeable surfaces means increased OF

how does burning fossil fuels cause flooding?

increase in global temperatures increases melt water which increases river discharge

how does agriculture cause flooding?

when the soil is left bare there is increased OF

where is the three gorges dam?

yangateze river in china

why was the three gorges dam built?

- generate electricity

- control flooding

what are advantages of the three gorges dam?

- sustainable electricity

- improve water transport along its length

what are disadvantages of the three gorges dam?

- around 1m people lost their homes

- expensive

- increased earthquake risk

- human & industrial waste trapped behind the dam

- flooded some of the country's most fertile land

where is the SNWTP?

north china plain, particularly around the mega cities of beijing and tianjin

what is the SNWTP?

the south-north water transport project is a large scale water transfer scheme to transfer significant quantities of water from china's humid south to arid north

why was the SNWTP needed?

- water demand was significantly greater than water availability

- move water from humid areas where supply is sufficient

what are advantages of the SNWTP?

- less health risks as there is more access to safe water

- more water for irrigation so there is increased food production

- more water for industries

what are disadvantages of the SNWTP?

- very expensive and burden on tax payers

- high displacement to make way for transfer routes

- wildlife and ecosystems are badly disturbed by transport routes

- loss of water from evaporation from open canals

- over-abstraction form the south can lead to water shortages

how do dams reduce flooding?

they store water and regulate river flow

how does embankment reduce flooding?

increases channel capacity

how does dredging reduce river flooding?

rubbish and sediment are dug up from under the river

how does channel straightening and flood relief channel reduce river flooding?

bypass meanders to increase the speed of the river

how do wetlands help control flooding?

they absorb extra runoff from heavy rains

how does floodplain zoning help control river flooding?

constructing houses and buildings furthest from the river

what is a fragile environment?

places that are sensitive to change and easily damaged so struggle to recover

what is desertification?

the spread of arid or desert-like conditions into semi-arid areas

what environments are at the most risk of desertification?

semi arid environments (savannah grasslands)

what is population?

number of species living in a given area

what is population growth rate?

change in population expressed as a percentage

what does the ecological footprint measure?

human demand on nature

what does bio capacity measure?

productivity of a region's ecological assets

what is soil erosion?

the movement and transport of the upper layer of soil (topsoil) by water, wind or mass movement

what is deforestation?

the felling and clearing of trees over a large area

what is drought?

a lack of precipitation over an extended period of time

what is migration?

the permanent movement of people from one place to another

what is groundwater extraction?

the removal of water from aquifers at a rate that doesn't give it time to replenish

what is conflict?

a serious disagreement between different parties that may result in on-the-ground fighting

what is climate change?

changes in the earth's climate due to the anthropogenic release of greenhouse gases

what is over-grazing?

when too many animals graze without giving the vegetation time to recover. the vegetation cover is depleted leaving unprotected patches of soil that erode away

what is over-cultivation?

growing crops year after year on the same land to the point where productivity falls due to soil erosion

how does heavy rainfall cause flooding?

since the rain is heavy it exceeds the rate on infiltration so enters the river by OF

how does prolonged rainfall cause flooding?

runoff is speeded as the ground becomes saturated

what is infiltration rate?

rate at which water enters the soil

what is infiltration capacity?

the maximum amount of water that the soil can absorb

what are the two factors that cause flooding?

human and physical factors

how long in advance do floods need to be predicted?

10 days

where are weather forecasts used effectively?

HICs

give physical factors that cause flooding

- heavy rainfall

- prolonged rainfall

- vegetation

- snow melt

- relief

give human factors that cause flooding

- agriculture

- deforestation

- urbanisation

- burning fossil fuels

why is it difficult to predict flood events in local places?

- poor funding

- less resources and data

- poor technology

what is needed for weather forecasts to be used effectively?

- other events happening around

- geographical contours

what are the 4 taps of singapore?

1. imported water

2. catchment water

3. NEWater

4. desalination

what is desalination?

removing salt from sea water

what makes up the largest part of an EF?

CO2 emissions

how does settlement cause deforestation?

to make space for housing, roads, public services (hospitals and schools) and areas to grow food

how does HEP cause deforestation?

dam construction requires large areas of land to be flooded to make reservoirs

how does logging cause deforestation?

need wood for furniture

how does agriculture cause deforestation?

areas of tropical rainforest are cleared for fields

what is subsistence agriculture?

farmers produce enough for themselves and their families and do not enter the cash economy at all

what is commercial agriculture?

farming for a profit

the impacts of desertification can be categorised into

environmental, social & economic