Saturday, September 24, 2005
GEOG - CLIMATIC HAZARDS
Droughts: unusually long dry period when there is a shortage of water for human, animal use, cultivation
-due to prolonged period of reduction of rainfall ovr an area which causes less water stored in grd, rivers
Effects: 1. farming: ground too dry for crops and plants to grow well and healthily > expensive
2. increased meat price: higher price of animal feed
3. loss of crops & death of livestock
4. famine: insufficient food
Sahel: long belt of land bordering the southern part of the Sahara, stretches 5000km right across Africa
-frm Mauritania & Senegal to Sudan & Ethopia
-annual rainfall btwn 300mm-600mm
-savannah: tall grasses, scrubs & scattered trees
Desertification: 1. climatic change: low rainfall, drying up of land & water bodies, vegetation dies, barren ground, soil erosion
2. overcultivation: no time for replenishing of nutrients, soil structure destroyed, soil erosion
3. deforestation: less interception, fewer roots to bind soil, ground exposed, soil erosion
4. overgrazing: grass cannot re-establish, soil structure destroyed, soil erosion
Causes: 1. droughts: baked land is difficult to plough & useless for grazing; bush fires destroy grassland & crops; top soil is converted to dust
2. overcultivation: rapid population growth; need for more food; land is not given time to rest
-makes soil susceptible to soil erosion
3. deforestation: increased population: trees cut down to provide wood; fewer roots; erosion
4. overgrazing: nomadic tribes try to enlarge their livestock; hooves destroy soil structure
Effects: 1. malnutrition, starvation, famines, diseases
2. ecological refugees: farmers moved to cities
3. walk further for water & firewood
Measures to prevent: 1. sinking >1500 wells in Mali for growing vegetables
2. practise water harvesting: create small stone walls to interrupt rainfall so it infiltrates into soil
3. planting trees in Senegal, Ethiopia: reduce wind velocity, protect top soil from erosion
Floods: body of water that covers usually dry area
Factors: 1.basin size, shape, relief: smaller and more circular basin, steep sided: shorter lag time
2. types of precipitation: prolonged heavy rain, intense storms: saturated ground, more surface runoff
snow: water held in storage, river level drops; reaches river when temperature rises & snow melts
3. landuse: vegetation intercepts rainfall, reduce throughflow; water cannot infiltrate concrtete, water is carried quickly to rivers via drains & gutters
4. permeability: permeable rocks allow rapid infiltration; sandy soil more porous, allow rapid infiltration; clays less porous, more surface runoff
5. storm surges: when water in the sea is raised to a great height by strong onshore winds blowing ovr it
-gigantic wave formed that breaks upon the land & floods it when it reaches the coast
Effects: 1. destroy dams & other structures & habitats
2, sweep away people & property
3. disrupt water & electricity supply, communications
4. widespread famine, diseases: cholera, typhoid fvr
Benefits: 1. fertile soil: alluvium deposits in water
2. irrigation: readily available water
3. gentle relief: favour farming & settlements; easy to build houses & use machines
4. cheap & easy water transport
5. some ppl are ignorant of disastrous consequences
Prevention: 1. channelisation: deepening, widening, clearing or lining of river channel with concrete: water flow away faster (expensive & impractical)
2. building levees: reinforce & increase height of river’s sides to reduce risk of flooding (however, if water goes beyond them, they prevent water frm flowing back into the river
3. building a dam across a valley: allows the control of the amt of water & can be used for electricity (expensive; some valleys unsuitable; affect env)
Case study: Bangladesh: causes: 1. low relief: flood plain & delta occupy 80%; land mostly 10m>sea
2. land drainage: ganges, brahmaputra, meghna brg in 2billion tonnes of sediment/yr, raise beds
3. snow melt: may & june: himalayans mtns snow melt
4. monsoon rain: southwest monsoon brgs heavy rainfall; grnd is saturated; increased surface runoff
5. storm surges: april-may, sep-nov, tropical cyclones
-narrowness of bay of Bengal force storm surge to move inland & flood low lying areas
6. deforestation: firewood, construction, agriculture
Effects: water borne diseases contaminated water
Nov1970: 8m high, powerful winds, 80% rice
Sep 1988: 75% flooded, rds & bridges damaged
1991: 6m high, 1milion tones of rice washed into sea
Tropical storms: violent swirling winds; intense low pressure systems; accompanied by strong winds
-originate ovr seas & oceans (btwn 6oN/S & 20oN/S)
-in summer & autumn (sea surface >27oC)
Formation: 1. air ovr oceans get heat, expand & rise
2. creates low pressure>air frm surrounding rush in a spiralling manner to replace rising warm air
3. air may spin at 200km/h, absorbs large amt of moisture; forms cumulonimbus & heavy rain
4. fades as it reaches land as no more moist air
-calm dry weather in eye (30-50kmD) lowest pressure due to descending cold air
-surrounded by wall of high cumulonimbus clouds under which experiences strong winds & heavy rain
-moist air is drawn to eye
-spirals anti clockwise in N hemi & vice versa
Effects: orissa state, India in 1999: cyclone 300km/h
-released much rain; fast & sudden
-ppl unprepared: 9000 died 200000 houses destroyed; livestock drowned
-international aid called in to help deal with victims
YESSSSS! DONE TYPING GEOG NOTESSS! :))))) this time is wrg it is FOUR FORTY EIGHT AM IN THE MORNING NOW. i shall go slp aft printing them out heeheehee. - lala
-due to prolonged period of reduction of rainfall ovr an area which causes less water stored in grd, rivers
Effects: 1. farming: ground too dry for crops and plants to grow well and healthily > expensive
2. increased meat price: higher price of animal feed
3. loss of crops & death of livestock
4. famine: insufficient food
Sahel: long belt of land bordering the southern part of the Sahara, stretches 5000km right across Africa
-frm Mauritania & Senegal to Sudan & Ethopia
-annual rainfall btwn 300mm-600mm
-savannah: tall grasses, scrubs & scattered trees
Desertification: 1. climatic change: low rainfall, drying up of land & water bodies, vegetation dies, barren ground, soil erosion
2. overcultivation: no time for replenishing of nutrients, soil structure destroyed, soil erosion
3. deforestation: less interception, fewer roots to bind soil, ground exposed, soil erosion
4. overgrazing: grass cannot re-establish, soil structure destroyed, soil erosion
Causes: 1. droughts: baked land is difficult to plough & useless for grazing; bush fires destroy grassland & crops; top soil is converted to dust
2. overcultivation: rapid population growth; need for more food; land is not given time to rest
-makes soil susceptible to soil erosion
3. deforestation: increased population: trees cut down to provide wood; fewer roots; erosion
4. overgrazing: nomadic tribes try to enlarge their livestock; hooves destroy soil structure
Effects: 1. malnutrition, starvation, famines, diseases
2. ecological refugees: farmers moved to cities
3. walk further for water & firewood
Measures to prevent: 1. sinking >1500 wells in Mali for growing vegetables
2. practise water harvesting: create small stone walls to interrupt rainfall so it infiltrates into soil
3. planting trees in Senegal, Ethiopia: reduce wind velocity, protect top soil from erosion
Floods: body of water that covers usually dry area
Factors: 1.basin size, shape, relief: smaller and more circular basin, steep sided: shorter lag time
2. types of precipitation: prolonged heavy rain, intense storms: saturated ground, more surface runoff
snow: water held in storage, river level drops; reaches river when temperature rises & snow melts
3. landuse: vegetation intercepts rainfall, reduce throughflow; water cannot infiltrate concrtete, water is carried quickly to rivers via drains & gutters
4. permeability: permeable rocks allow rapid infiltration; sandy soil more porous, allow rapid infiltration; clays less porous, more surface runoff
5. storm surges: when water in the sea is raised to a great height by strong onshore winds blowing ovr it
-gigantic wave formed that breaks upon the land & floods it when it reaches the coast
Effects: 1. destroy dams & other structures & habitats
2, sweep away people & property
3. disrupt water & electricity supply, communications
4. widespread famine, diseases: cholera, typhoid fvr
Benefits: 1. fertile soil: alluvium deposits in water
2. irrigation: readily available water
3. gentle relief: favour farming & settlements; easy to build houses & use machines
4. cheap & easy water transport
5. some ppl are ignorant of disastrous consequences
Prevention: 1. channelisation: deepening, widening, clearing or lining of river channel with concrete: water flow away faster (expensive & impractical)
2. building levees: reinforce & increase height of river’s sides to reduce risk of flooding (however, if water goes beyond them, they prevent water frm flowing back into the river
3. building a dam across a valley: allows the control of the amt of water & can be used for electricity (expensive; some valleys unsuitable; affect env)
Case study: Bangladesh: causes: 1. low relief: flood plain & delta occupy 80%; land mostly 10m>sea
2. land drainage: ganges, brahmaputra, meghna brg in 2billion tonnes of sediment/yr, raise beds
3. snow melt: may & june: himalayans mtns snow melt
4. monsoon rain: southwest monsoon brgs heavy rainfall; grnd is saturated; increased surface runoff
5. storm surges: april-may, sep-nov, tropical cyclones
-narrowness of bay of Bengal force storm surge to move inland & flood low lying areas
6. deforestation: firewood, construction, agriculture
Effects: water borne diseases contaminated water
Nov1970: 8m high, powerful winds, 80% rice
Sep 1988: 75% flooded, rds & bridges damaged
1991: 6m high, 1milion tones of rice washed into sea
Tropical storms: violent swirling winds; intense low pressure systems; accompanied by strong winds
-originate ovr seas & oceans (btwn 6oN/S & 20oN/S)
-in summer & autumn (sea surface >27oC)
Formation: 1. air ovr oceans get heat, expand & rise
2. creates low pressure>air frm surrounding rush in a spiralling manner to replace rising warm air
3. air may spin at 200km/h, absorbs large amt of moisture; forms cumulonimbus & heavy rain
4. fades as it reaches land as no more moist air
-calm dry weather in eye (30-50kmD) lowest pressure due to descending cold air
-surrounded by wall of high cumulonimbus clouds under which experiences strong winds & heavy rain
-moist air is drawn to eye
-spirals anti clockwise in N hemi & vice versa
Effects: orissa state, India in 1999: cyclone 300km/h
-released much rain; fast & sudden
-ppl unprepared: 9000 died 200000 houses destroyed; livestock drowned
-international aid called in to help deal with victims
YESSSSS! DONE TYPING GEOG NOTESSS! :))))) this time is wrg it is FOUR FORTY EIGHT AM IN THE MORNING NOW. i shall go slp aft printing them out heeheehee. - lala
# we mugged! @ 1:46 PM 
