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Geography - Physical - Paper 1 > Water - EQ2 - > Flashcards

Water - EQ2 - Flashcards

1
Q

Define drought

A
  • an extended period (a season, year or several) of deficient rainfall relative to the statistical multi year average for a region
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2
Q

An im…… of ….&…. of water can have serious implications for the hydrological cycle

A
  • imbalance
  • inputs & outputs
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3
Q

A ….. (more commonly known as a drought) refers to when input is less than output

A
  • deficit
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4
Q

What are the 5 key types of drought

A
  • socio-economic
  • agricultural
  • meteorlogical
  • hydrological
  • ecological
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5
Q

Define meteorlogical drought

A
  • a shortfall or deficiency of water over an extended period, usually at least a season
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6
Q

What are the features of meteorlogical drought

A
  • Rainfall deficit
  • Low precipitation
  • High temperatures
  • Strong winds
  • Increased solar radiation
  • Reduced snow cover
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7
Q

What are some explicit impacts of meteorlogical drought

A
  • Loss of soil moisture
  • Irrigation supply drops
  • Reduction in water available for consumption
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8
Q

Causes of meteorlogical drought

  • Droughts can range from …………..&……….precipitation deficits to longer-term trends that are part of …………………
A
  • Droughts can range from** short-term and localised** precipitation deficits to longer-term trends that are part of climate change
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9
Q

Causes of meteorlogical drought

  • Research suggests that …………………………… are an important causal factor in short-term precipitation deficits
A
  • Research suggests that sea surface temperature anomalies are an important causal factor in short-term precipitation deficits.
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10
Q

Causes of meteorlogical drought

  • The physical causes of drought are only ………. understood
  • They lie somewhere in the complex interactions between ……. , ……. , …….. , …… & ……, which produces the climates of the globe
A
  • The physical causes of drought are only partially understood.
  • They lie somewhere in the complex interactions between atmosphere, oceans, cryosphere, biosphere and the land, which produces the climates of the globe.
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11
Q

Meterological drought is a ….. deficit

A

rainfall

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12
Q

Agriclutural drought is a ……. deficit

A

soil moisture

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13
Q

Hydrological drought is a …… deficit

A

stream flow

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14
Q

socio-economic drought is a……… defict

A

food

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15
Q

Define hydrological drought

A
  • low water supply in our irvers, lakes, aquifers, & other reservoirs that often follows meteorlogical drought
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16
Q

Define agricultural drought

A
  • drought when a water shortage significantly damages or destroys agricultural crops
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17
Q

Define socio-economic drought

A
  • dought refers to when a water shortage affects the supply & demand of drought commodities
  • e.g water food, grains & fish
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18
Q

Define ecological drought

A
  • the most recently defined type of drought
  • refers to the widespread ecological damage caused by the lack of soil moisture
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19
Q

What are the features of hydrological drought

A
  • Reduced infiltration
  • Low soil moisture
  • Little percolation and groundwater recharge
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20
Q

What are the features of agricultural drought

A
  • Low evapotranspiration
  • Reduced biomass
  • Fall in groundwater level
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21
Q

What are the features of socio-economic drought

A
  • Loss of vegetation
  • Increased risk of wildfires
  • Soil erosion
  • desertification
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22
Q

What are the impacts of hydrological drought

A
  • Reduced storage in lakes and reservoirs
  • Less water for urban supply
  • Poorer water quality
  • Threats to wetlands and habitats
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23
Q

What are the impacts of agricultural drought

A
  • Poor yields from rainfed crops
  • Failing irrigation systems
  • Livestock productivity falls
  • Rural industries affected
  • Government aid may be required
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24
Q

What are the impacts of socio-economic drought

A
  • Widespread failure of agricultural systems
  • Food shortages
  • Rural economy collapses
  • Rural to urban migration International aid required
  • Humanitarian crisis
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25
Q

Water is ……. distributed …. across the globe

A
  • spatially
  • unevenly
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26
Q

…% of the world’s population live in areas which only have access to …% of the world’s annual rainfall

A

66% of the world’s population live in areas which only have access to 25% of the world’s annual rainfall

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27
Q

…..% of the worl’d land area has some level of drought exposure

A

38%

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28
Q

Causes of meteorological drought

Explain how global atmospheric circulation can cause meteorological drought

A
  • Heat is greatest at the equator due to the concentration of the sun’s energy
  • This causes air to rise at the equator (the driving force of the whole model)
  • This air then cools and condenses creating rain (hence tropical rainforests)
  • Air cools and sinks at around 30 degrees N and S of the equator creating subtropical high-pressure belts
  • As air is sinking no clouds form and so these areas are dry (worlds major deserts)
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29
Q

Causes of meteorolgical drought

What is the ITCZ

A
  • The Intertropical Convergence Zone, or ITCZ,
  • is a band of low pressure around the Earth which generally lies near to the equator
  • The trade winds of the northern and southern hemispheres come together here, which leads to the development of frequent thunderstorms and heavy rain
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30
Q

Causes of meteorolgical drought

What is the impact of season shifts in the ITCZ

A
  • Seasonal shifts in the location of the ITCZ drastically affects rainfall in many equatorial nations,
  • resulting in the wet and dry seasons of the tropics
  • rather than the cold and warm seasons of higher latitudes
  • Longer term changes in the ITCZ can result in severe droughts or flooding in nearby areas
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31
Q

Causes of meteorolgical drought

  • Longer term changes in the ITCZ can result in……
A
  • Longer term changes in the ITCZ can result in severe droughts or flooding in nearby areas
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32
Q

…% of the global population are vulnerable to severe drought

A

18%

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33
Q

What is the air pressure 90 degrees from the equator

A

high pressure - clear, sunnier weather

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34
Q

What is the air pressure 60 degrees from the equator

A

low pressure - rainy weather

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35
Q

What is the air pressure 30 degrees from the equator

A

high pressure - clear, sunnier weather

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36
Q

What is the air pressure at the equator

A

low pressure - rainy weather

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37
Q

The ITCZ moves ………. as the planet …….
When it moves it brings the monsoon to India, when it moves to South, India returns to…..

A

The ITCZ moves seasonally as the planet tilts
When it moves it brings the monsoon to India, when it moves South, India returns to drought conditions

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38
Q

What is blocked weather

A
  • Usually, weather fronts (which bring rain) move from w to e across the UK,
  • but sometimes they can staywhere they are, or even go from e to w, & this is usually due to a ‘block’
  • This means a big area of high pressure is remaining almost stationary over the samearea for a long time
  • The high pressure can stop weather fronts moving past it, so that they skirt around the edges, or stay where they are for an extended period
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39
Q

what is a blocking anti-cyclone

A
  • the winds tend to be light & blow in a clockwise direction, the air is descending, which stops the formation of clouds
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40
Q

What is an example of a blocking anti-cyclone

A
  • European heatwave where UK hit 40 degrees in 2021
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41
Q

What does ENSO stand for

A
  • El Nino Southern Oscillation
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42
Q

What are the 2 events in ENSO

A
  • El Nino
  • La Nina
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43
Q

During El Niño, winds and ocean currents across the……, …….. direction.
This changes the weather patterns around the Pacific.
Occurs every ……….years, although they appear to be getting……..

A
  • Pacific, change
  • 3 – 7
  • more regular
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44
Q

How long do El Nino events usually last

A
  • 18 months ish
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45
Q

What are the conditions in the Pacific Basin in a normal year

A
  • Trade Winds blow from east yo west along the equator
  • This moves warm surface water towards the western Pacific
  • cold water upwells up along the west coast of S. America (near Peru)
  • Warm moist air rises, cools & condenses there forming rain clouds in the West
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46
Q

What is upwelling

A
  • an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water from deep water
  • towards the ocean surface,
  • replacing the warmer, usually nutrient-depleted surface water
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47
Q

What are the conditions in the Pacific Ocean during El Nino

A
  • Air pressure over West coast of S. America becomes low & air pressure over west Australia becomes high
  • The normal east to west trade winds over Pacific are disrupted
  • it may slacken or even reverse & this has a knock on effect on the ocean currents
  • warm water ‘sloshes’ eastwards
  • No upwelling on S. American coast
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48
Q

Describe the effect on water temperatures from El Nino

A
  • When this happens, cool water normally found along the coast of Peru is replaced by warmer water
  • At the same time, the area of warmer water further west, near Australia and Indonesia, is replaced by cooler water
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49
Q

El Niño events seem to trigger ……….. conditions throughout the world, usually in the ……… year
For example,….

A

El Niño events seem to trigger very dry conditions throughout the world, usually in the second year
For example, the monsoon rains in India and South East Asia often fail.

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50
Q

Why is upwelling important for fish stocks in Peru

A
  • With the movement of warm water back eastwards, it prevents any upwelling of cold nutrient-rich, water on which Plankton feed
  • Plankton is the main food of the anchovy which is one of the main fishing types in Peru
  • Warm water also expands,
  • so as the water piles back East towards Peru sea levels increase by 30cm
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51
Q

Define thermocline

A
  • The boundary in the ocean between warm surface water and cold deep water
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52
Q

What is La Nina

A
  • Occasionally as an El Niño year dies out, a third weather condition arises: La Niña
  • All it is, is an exaggerated version of normal conditions
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53
Q

Describe what happens in La Nina

A
  • Air pressure is unusually high over the west coast of South America and low over eastern Australia
  • As warm water is pushed westwards, sea levels rise by up to 1m
  • Around Indonesia and Philippines, strong uplift of air (very strong air circulation) leads to heavy rain
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54
Q

La Nina can lead to ………, particularly on the ….. coast of …….. …….

A

La Nina can lead to severe drought conditions, particularly on the Western Coast of South America

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55
Q

List some of the anthropogenic causes of drought

A
  • deforestation
  • dam construction/ river diversion
  • over abstraction
  • poor agricultural practises -over grazing
  • micro climate changes -urbanisation
  • climate change
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56
Q

what is a microclimate

A
  • tthe distinctive climate of a small-scale area e.g a park, garden or part of a city
  • the weather varaibles in a microclimate, such as temp, rainfall, wind or humidity
  • may be subtly different from the conditions prevailing over the area as a whole, varying from whats expected under certain types of pressure or cloud cover
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57
Q

Define desertification

A
  • the process by which once-productive fertile land gradually changes into a desert-like landscape
  • it usually takes place in semi-arid land on the edges of existing deserts
  • it is not neccessarily irreversible
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58
Q

How does global warming lead to desertification

A
  • increase in average climactic temperatures
  • increased rate of evaporation of water moisture especially in tropical or sub-saharan climates
  • if more moisture has evaporated, less will be available for convectional rainfall
  • so plant growth will be stunted & vegetation dies
  • leading to desertification
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59
Q

How does reduced precipitation lead to desertification

A
  • changing rainfall patterns - less reilable, seasonally & annually
  • the occassional drought year sometimes extends to several years
  • as vegetation dies, the protective layer it provides for soil will also be removed
  • soil is increasingly exposed to wind & rain
  • accellerates soil erosion, as short intense rainfall makes it difficult for soil to capture & store it
  • positive feedback loop of worsening soil conditions & vegetation death
  • leading to desertification
60
Q

Explain the human causes of desertfication which create a positive feedback loop

A
  • population growth is the root cause of recent increase in rates of desertifcation
  • demand for food, water & other resources also increases
  • this leads to over cultivation & overgrazing (intense cattle farming), so intense use of marginal land exhausts soil
  • also, deforestation via burning of trees exposes top soil to erosion, & worsens quality
61
Q

What is the situation with the Sahel Drought, Africa 2011-12

A
  • The northern Sahel region is experiencing a 30-40% annual departure from ormal rainfall
  • things have been exacerbated by frequent civil war & unprescedented levls of organised violence in 2018 - food & livestock deliberately destroyed
62
Q

Human factors act like a …………………. …………., humans enhance the impacts of drought by…

A
  • feedback loop
  • the overanstraction of surface water from rivers & ponds, & groundwater from aquifers
63
Q

What are the impacts of the Sahel Drought

A
  • 4.2 million displaced people
  • protracted armed violence exacerbates the situation of food insecurity, malnutrition & epidemics
  • farming & trade severely impaired
  • high concentrations of herds in pastoral enclaves, & natural reserves where risks of epizootic diseases are high
  • 9.7 million people vulnerable to food insecurity —> high malnutrition rates
64
Q

Describe the responses to the Sahel Drought

A
  • 5 wells rehabilitated
  • redistribution of animals & agricultural kits
  • vaccinating 500,000 animals
  • BUT there is a funding gap of 73.5% - $122.6 million
65
Q

What is the situation with the Australia Drought 1997-2009

A
  • prone to drought as Ocenia spans the latitudes of the subtropical high pressure belt
  • this means most the country’s rainfalll is low & erratic
  • they experienced over a decade of below average rainfall, 30% affected by serious or severe rainfall deficiency
66
Q

What were the consequences to Australias’ drought

A
  • death of livestock
  • 33 wetlands temporarily disconnected to help save water
  • pipelines had to be built to deliver drinking water to lower lake communities
67
Q

How has Australia’s drought been managed

A
  • Unlike the Sahel, Australia has not followed the same downward spiral of desertification
  • a careful management of scarce water resources, & sorting out the competing demands of irrigation & urban dwelllers has also stopped this happening
  • also large scale recycling of grey water
  • csonstructing desalination plants
  • devising new water conservation strategies
68
Q

Give an example of an issue with an Australian water conservation strategies

A
  • Western Corridor Recycled Water Scheme
  • faced community resistance as treated waste water will never be safe enough to drink
69
Q

Define ecosystem functioning

A
  • refers to the biological, chemical, and physical processes that take place within the ecosystem
70
Q

Define ecosystem resilience

A
  • the capacity of an ecosystem to respond to disturbance from it’s normal state by resisting damage and recovering quickly
71
Q

What is the impact of drought on Forest Ecosystems

A
  • Living trees take 2-4 years to recover and resume normal growth rates following a period of drought
  • Long-term harm drought-stressed trees includes foliage loss, impairing growth, lasting damage to tissues within the tree impairing water transport —> increased susceptibility of pines & firs to fungal diseases
  • Significant die-off of certain species e.g - Pinon pines —> can reduce carbon sequestration
72
Q

What is the impact of drought on Wetland Ecosystems

A
  • reduced interception causes vegetation to wilt & die
  • this results in less soil nutrients, impacting rest of food web
  • progressive loss of habitat as open water source shrinks, reducing soil moisture –> eroison
  • some land species will be affected as the dry soil will be less penetrable, limiting their ability to get food
73
Q

What is the value of Wetlands that has been discovered over the last 50 years

A
  • Wetlands currently cover about 10% of the Earth’s land surface
  • & until 50 years ago they were considered as wastelands, only good for draining and infilling to provide building land
  • However, it is now understood that wetlands perform a number of important functions: from acting as temporary water stores to the recharging of aquifers, from giant filters trapping pollutants to providing nurseries for fish and feeding sites for migrating birds
74
Q

Brazil Drought - Amazon Rainforest

In 2014, climate scientists reported that deforestation in the Amazon may now have…

A
  • passed a tipping point - in other words, changing hydrological and climatic cycles permanently
75
Q

Brazil Drought - Amazon Rainforest

What is the cause of drought in the Amazon Rainforest

A
  • Rainforests recycle half of their rainfall, but the positive feedback loop of deforestation and less rainfall is reducing the ability of the rainforest to regenerate
  • This makes fragile rainforest ecosystems less resilient
  • Thinning forests have reduced soil water storage and evapotranspiration
  • In turn, these lead to changing weather patterns - with lower precipitation
76
Q

Brazil Drought - Amazon Rainforest

Why are tropical stores & fluxes really important

A
  • forests regulate regional climate and generate flows of moisture across the continent
  • Now, the combined risk of global climate change, ENSO cycles & deforestation will probably alter this so that extreme weather will become more frequent
77
Q

Brazil Drought - Amazon Rainforest

What is the impact of drought

A
  • the Amazon rainforest’s capacity to absorb carbon will decline
  • regional water cycles will change and soil temperatures will increase
  • the Amazon rainforest will be replaced with savannah-like grasslands
  • more wildfires will increase the level of carbon in the atmosphere
  • reduced rainfall will threaten Brazil’s dependency on HEP (which generates 70% of its electricity)
78
Q

Where is flooding always a possibility

A
  • Floods in areas experiencing meteorlogical conditions providing a lot of precipitation flooding
79
Q

Flooding can occur as ………………. or as ………..

A
  • fast onset ‘flashfloods’ or as slower onset hazards
80
Q

When does the most common form of flooding occur

A
  • when a river reaches & then exceeds bankful discharge,
  • additional water cannot be contained within the channel
  • & so spills onto the surrouding land,
  • making the floodplains innundated with water
81
Q

List the 5 meteorlogical causes of droughts

A
  • Intense Storms
  • Prolonged rainfall
  • Heavy rainfall
  • Snowmelt
  • Monsson rains
82
Q

Intense storns

For example, ………… bring a lot of rainfall in a realtively ………., often without …………

A

Tropical cyclones bring a lot of rainfall in a relatively short time period, often without warning

83
Q

Intense storns

What happens when intense storns bring a lot of rainfall in a very short period of time

A
  • water moves quickly into channels, as it is unable to soak into the ground causing them to overflow their banks
84
Q

Intense storns

Where are flashfloods common

A
  • arid
  • semi-arid areas
  • mountainous areas
85
Q

Intense storns

What are flash floods

A
  • In arid & semi-arid areas, occassional thunderstorms drop a lot of rain suddenly which runs quickly over the baked ground, creating ‘flash floods’
86
Q

Flashfloods can be characterised by ………

A
  • short lag-times
87
Q

What causes prolonged rainfall

A
  • persistent rain over a long period of tine, perhaps the result of several low pressure systems (depressions) passing over an area, causes a sequence of frontal rainfall
  • In the UK, deep dpressions can cause this
88
Q

Define depressions

A
  • a system of low pressure, with fronts of precipitation where low & high pressure air masses meet
89
Q

How does prolonged rainfall cause prolonged rainfall

A
  • first the soil is saturated so that later rainfall cannot infiltrate
  • runoff is increased & quickly enters river channels, causing floods
90
Q

Heavy Rainfalll

  1. What causes heavy rainfall
A
  • a cold front in a low pressure system can cause a lot of rain to fall over a short period of time
91
Q

Heavy Rainfall

  1. how does heavy rainfall cause flooding
A
  • intense rainfall in a short time period can be too much to allow throughflow or groundwater flow to take place,
  • so the excess waterquickly runs off the surface & into the river channels where discharges increase to exceed flood levels
92
Q

Snowmelt

1 . Where is winter snowfall highest

A

In some mountainous regions, winter snowfall accumulates to a considerable depth

93
Q

Snowmelt

  1. ……. temperatures in Spring cause snow to…..
A

warmer
rapidly start melting

94
Q

Snowmelt

  1. Describe the rapid snowmelt that can occur in spring in some mountainous regions
A

The groundwater under the snow may still be frozen so a lot of the melt water flows rapidly down steep sloped into river valleys, casuing increased river discharges

95
Q

Where does snowmelt cause meterological flooding

A
  • The plains of Siberia
96
Q

Define monsoon

A
  • The drastic variation between wet and dry seasons for sub-tropical
    areas, caused by a changed prevailing wind
  • Can lead to annual flooding
97
Q

Which areas get monsoon rain

A
  • subtropical areas have a wet season, these are especially wet land areas between mountains & warmer oceans (e.g India)
98
Q

How do monsson rains cause flooding

A
  • Monsoon seasons are charaterised by torrential rainfall, which initially falls onto hard, dry ground –> increasing run off,
  • & then onto staurated ground
  • with the months of heavy rainfall adding to runoff & increasing river levels until they flood
99
Q

What are flood data bases used for

A
  • to analyse long-term trends
100
Q

What is the EM-DAT database

A
  • shows floods that appear to be increasing in frequency & severity largely due to climate change & increasingly popularity pressure e.g Central Europe
101
Q

What is FLOPROS

A
  • Flood Protection Standards Global Database
102
Q

What is Flood Protection Standards Global Database

A
  • assesses flood risk by analysing the links between the flood return period & flood protection measures
  • it combines information on flood portection measures & policies within a modelling approach
  • the data output does not take into account future change e.g climate or population
103
Q

What is tidal fooding often the result of

A
  • Often a result of storm surges or when high river flows meet particularly high spring tides in estuaries
104
Q

What causes a storm surge

A
  • caused by very low air pressure which raises the height of the hightide sea
  • strong onshore winds then drive the raised sea towards the coast , often breeching coastal defences & flooding large areas
105
Q

Which types of land areas are even more susceptible/vulnerable to surpluses in water

A
  • low-lying land, the base of river valleys & estuaries
  • urbanised, built environments
  • small basins, esp in semi & arid areas
106
Q

Why are low-lying land like the base of river valleys & estuaries more vulnerables to surpluses

A
  • river flooding can occur along with groundwater flooding as the ground becomes saturated,
  • therefore any surface close to the water table is vulnerable
107
Q

Why are urbanised, built environments more vulnerables to surpluses

A
  • impermeable surfaces increase surface runoff, reducing lagtime, so increasing the risk of flash flooding
108
Q

Why are small basins more vulnerables to surpluses

A
  • impermeable surfaces increase surface runoff, reducing lagtime, so increasing the risk of flash flooding
109
Q

Explain how the likelihood of flooding is also enhanced by other physical circumstances
* geology

A

where ground surface is underlain by impermeable rocks

110
Q

Explain how the likelihood of flooding is also enhanced by other physical circumstances
* sudden unusual melting

A

when ice dams suddenly melt & the water in glacial lakes are released

111
Q

Explain how the likelihood of flooding is also enhanced by other physical circumstances
* volcanoes

A
  • where volcanic activity generates meltwater beneath ice sheets that is suddenly released (jökulhlaup)
  • —> a glacial outburst flood that occurs when a lake fed by glacial meltwater breaks through its dam and drains rapidly
112
Q

Explain how the likelihood of flooding is also enhanced by other physical circumstances
* seismic activity

A

where earthquakes cause the failure of dams & landlsides that block users

113
Q

Bangladesh is a particularly food-prone country mainly because…..

A
  • it is a land of floodplains and deltas built up by mighty rivers such as the Ganges, Padma and Meghna
114
Q

Bangladesh

The Ganges, Padma and Meghna are swollen …… a year by….

A

twice a year
meltwater from the Himalayas, and by the summer monsoon

115
Q

Bangladesh

……. between the rivers and behind Chittagong are often victims of …………

A
  • Hilly tracts
  • flash floods
116
Q

In what time period was there particularly bad flooding in the UK

A
  • 2015/16 Winter Storm Season
117
Q

Where was the 2015/16 Winter Storm season in the UK really bad

A
  • North England, in particular, Cumbria, Scotland, Northern Ireland
118
Q

2015/16 Storm Season

Where did record peak flows occur in the UK

A
  • River Tynes & Eden in Scotland
  • Clyde & Tay in Scotland
119
Q

2015/16 Storm Season

Large areas of the UK recorded ………

A

more than double the average amount of rainfall

120
Q

What were the causes of the UK flooding 2015/16
-human causes

A
  • budget cuts on the amount of spending on flood defences
  • poor land management –> blocked ditches
  • global warming
121
Q

What were the causes of the UK flooding 2015/16
-physical

A
  • low pressure weather systems, brought by the Jet Stream
  • prolonged heavy rainfall - orographc & convectional
122
Q

What were the causes of the UK flooding 2015/16
-international interferences

A
  • An EU directive that puts environmental conservation ahead of the regular dredging of rivers changed the sedient flux balance durastically
123
Q

What is realised by post-flood enquiries

A
  • flood protection methods are designed to cope with flood events of a given magnitude
  • when an event of very rare magnitue occurs, no amount of money or engineering is going to prevent the hoped degree of protection
124
Q

UK 2015/16 storm season

  • Storm Abigail was caused by
A
  • excessively saturated soils in early November
125
Q

UK 2015/16 storm season

What made flooding by Storm Desmond so bad

A
  • In Cunbria, over 1 months rainfall came in one day (convectional & orographic rainfall was combined with frontal rain)
126
Q

UK 2015/16 storm season

how many properties were damaged

A
  • 16,000
127
Q

UK 2015/16 storm season

how much compensation did the UK govt provide

A
  • £200 million
128
Q

UK 2015/16 storm season

Estimated total costs?

A
  • £5 billion
129
Q

UK 2015/16 storm season

Economic consequences?

A
  • businesses damaged
  • insurance costs
  • emergency crises
  • consumers & deliveries unable to reach businesses
130
Q

UK 2015/16 storm season

Infrastructure costs?

A
  • roads & railways blocked
  • healthcare disruptions
  • power cuts
  • schools closed
131
Q

UK 2015/16 storm season

Costs to settlements?

A
  • property damaged
  • people evacuated
  • sediment deposited in houses
132
Q

Give 4 examples of positive environmental impacts of flooding

A
  • recharged groundwater stores
  • increased connectivity between aquatic habitats - triggering larger migration, dispersal & breeding events
  • soil replenishment by the movement of sediment
133
Q

Elaborate on the positive impact on soils of flooding

A
  • soils may become waterlogged on level ground or scoured away on sloped by increased surface flow
  • flood events reduce the microbial biomass in soil, but in th elong-term more nutrient rich sediments, esepcially on floodplains are provided
134
Q

Explain how most ecosystems can cope with flooding

A
  • Most ecosystems have a degree of ecological resilience that can cope with the effects of moderate flooding
  • small floods can replenish water levels creating wetland habitats & replenishing long-term nutrients
135
Q

Yet there is an extent to which floods are beneficial to ecosystems…

A
  • It is where the environment has been degraded human activities that negative impacts are more evident (extreme floods & degredation)
136
Q

the removal of soil and sediment by floodwaters can lead to the ……………of water bodies

A
  • eutrophication
137
Q

That same floodwater can also……………………. with disastrous effects for ……………………….., while …………….. carried by floodwater can weaken or kill trees, which in turn means…..

A
  • leach pollutants into water courses
  • aquatic wildlife & ecosystems
  • diseases
  • plant biomass & invertebraes are reduced
138
Q

What other forms of pollution during meteorlogical floods can harm aqautic ecosystems

A
  • nitrates, chemicals & heavy metals
139
Q

Th degree of threat posed by floods depends on…

A
  • the depth & velocity of the water
  • e.g wtaer 0.5m deep can wash cars away & cause building foundations to collapse
140
Q

Describe how human actions can increase flood risk

Floodplain use

A
  • population pressures & rural-urban migration increase building on floodplains
  • depite flood protection methods, major floods can still occur
141
Q

Describe how human actions can increase flood risk

Land use change

A

removal of natural vegetation, especially deforestation, changes hydrological processes in th catchment area
increased soil erosion adds sediment to river channels, changing the basin shape & reducing the capacity, so floods can occur with a lower discharge

142
Q

What are examples of land use change that increase flood risk

A
  • impermeable areas of tarmac, sprinkling of groundwater onto arable crops
  • streams channellled into currents to aid rapid drainage of farmalbd
  • ploughing & grazing compacts soil
143
Q

Describe how human actions can increase flood risk

River management - channelisation

A
  • an effective way of improving river discharge & reducing floodrisk
  • but simply displaces the river flow downstream, overwhelming these locations during peak discharge
144
Q

Describe how human actions can increase flood risk

River management - dams

A
  • dams block the flow of sediment down a river, so the reservoir graduallly fills up with silt; downstream there is increased river bed erosion
145
Q

Describe how human actions can increase flood risk

River management - embankments

A
  • embankments are built to improve bankful capacity,
  • using concrete or sustainable materials (usually dredged from the channel)
  • however, if these are breached the scale of flooding is far greater

Geography - Physical - Paper 1 (17 decks)

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