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floods & droughts by Mind Map: floods & droughts
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floods & droughts

impacts of floods

loss of lives

floods provide fertile land to floodplains, attractive to farmers, densely populated, flood occurs unprepared

e.g. 2003 Huai River Basin, Anhui jiangsu, Henan China, 298 lives lost and forced people to evacuate

damage

environment, destroy plant lives and natural habitats of animals, e.g 17 July 2006, tsunami struck Java and flooded the coastal regions along southern part of island, cause several damage to coastal ecology, nature reserve near Pangandaran Beach badly affected

property, flood waters submerge villagers and towns, homes ruined, very costly, take a long time to repair, e.g 2005, Hurricane Katrina hit Gulf Coast of USA, lead to massive flooding of several states. damage cost:US$44 billion in total

infrastructure, roads become inaccessible, power supply and phone lines disrupted, cut off communication

spread of diseases

when flooding occurs, large no. of homeless victims, housed in overcrowded makeshift shelters, lack sanitation and clean drinking water, outbreak of diseases, e.g malaria and cholera

e.g Dhaka, Bangladesh in July 2004

fertile soil for agriculture

due to regular flooding of rivers, provides soil along river banks with fertile alluvium, soil suitable for farming, people continue living on low-lying plains near rivers despite risk of floods

e.g Nile Delta, Egypt, crops cultivated because of fertile alluvium deposited by River Nile

causes of floods

natural

excessive rain, tropical monsoon climate, results in heavy rain, overflow banks and cannot seep into ground, e.g China, Yangtze River and Yellow River, large amount of sediments, deposit on river bed, shallow river, flooding

storm surges, tropical storms, strong winds, raise waves, to exceptionally high levels, creates gigantic waves, crash into coast and flood land

melting snow, e.g 1986 St John River, Canada could not hold excess water, several homes submerged, several homes evacuated, cool temperate climate, melting snow in Spain, large amount of water in rivers, overflow and flood

global atmospheric processes, El Nino, 3-7 years(several weeks), warming of water surface, temperature of South America heats up, heavy rain at south eastern part of Pacific Ocean, La Nina, follows after El Nino, 3-5 years, south western part of Pacific Ocean, temperature increase, heavy rain off coast of Australia

movements of the Earth's surface, earthquakes, landslides, soil may loosen, deposited into river, overflow and flood surroundings, tsunamis, destroy coastal settlements, e.g 2004 Indian Ocean Tsunami, strong undersea earthquake near Sumatra

human

clearing of forests, e.g in China, forests are cleared to create land for housing and wood to use as fuels, hence, loosen soil and is eroded when rain falls, bare slopes left behind increase surface runoff, higher volume of water flow into rivers, at the same time, more deposition of materials on river bed, river becomes shallow, flood occurs

Urbanization, with increase of population, built-up areas increase, concrete pavements and tarred roads, less natural vegetation to intercept rain, increase in amount of suface runoff flowing into rivers, e.g London, River Thames experience regular flooding

Impacts of enhanced greenhouse effect, global warming, cause climatic changes like higher rainfall in wetter regions, increase in global temperatures, reduction of ice cover, rising sea levels

impacts of droughts

shortage

food, due to lack of water, animals and people die from dehydration, crops destroyed

water, as rivers and lakes dry up when there is a drought

e.g more than 3 million died from starvation and dehydration in mid-1980s due to severe droughts in Sahel region

damage to environment

in arid and semi-arid regions, prolonged droughts cause desertification, soil in region become very dry, unable to support vegetation growth, thus soil easily blown away by wind, barren land left behind

e.g Sahara Desert expanded southwards due to prolonged droughts which began in 1968

forest fires and hazes

no rain for long time, vegetation in forests becomes dry, catches fire easily, smoke spreads to neighbouring countries as winds blow across these forests, blankets entire cities in haze, affects environment and health of people, pollute air, breathing problems and eye irritations

causes of droughts

natural

insufficient rainfall, arid or semi-arid regions, monsoon winds delayed, dry season prolonged and droughts occur, e.g Bangladesh or India

global atmospheric processes, change in rainfall patterns due to natural phenomena, El Nino cause droughts in Indonesia and Australia in western Pacific, La Nina cause droughts in Peru of eastern Pacific

human

reduced forest cover, lower rates of transpiration, less water vapour in atmosphere, fewer clouds formed hence less rain, ground exposed to direct heating by Sun and soil dries up quickly, e.g deforestation in Amazon rainforest

impact of enhanced greenhouse effect, global warming cause droughts in drier regions, e.g Sahel, Africa, high temperatures cause rapid evaporation, dries up land, lakes and rivers

overuse of water, growing population, more water needed for homes, agriculture and industry, in some places, people depend heavily on groundwater and rivers to meet water needs, e.g since 2001, villagers of Kothariya, India have been experiencing drought, overuse of water, rivers and wells dried up and livestock affected too