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Arman Alluwie TP2 SHSS
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3 Express Pure Geog:Floods and Droughts19h April 2012Causes of Floods and Droughts
Arman Alluwie TP2 SHSS
2+Lesson Objectives
By the end of the lesson, we would have discussed the impact of floods and droughts on
human lives and the environments evaluate the effectiveness of management strategies
taken to mitigate and respond to floods and droughts
Arman Alluwie TP2 SHSS
3+Lesson Recap:Floods and Droughts Hazard
Definition: can endanger lives and destroy property
Flood Definition: occurs when land that is usually dry is
submerged by large amounts of water
Drought Definition: prolonged period with little or no rainfall normally occurs in regions which receive 250- 500
mm per year
Arman Alluwie TP2 SHSS
4+Lesson Recap:Causes of Floods Natural Causes
1. Excessive rainfall
2. Storm surges
3. Melting snow
4. Global atmospheric processes
5. Movements of the Earth’s surface
Human Causes1. Clearing of forests
2. Urban development
3. Impacts of enhanced greenhouse effect
Arman Alluwie TP2 SHSS
5+Causes of Droughts
Natural causes of droughts1. Delayed rain or insufficient rainfal
2. Global atmospheric processes
Human causes of droughts1. Reduced forest cover
2. Impact of enhanced greenhouse effect
3. Overuse of water
Arman Alluwie TP2 SHSS
6+Lesson Recap:Storm surges
http://www.nhc.noaa.gov/surge/animations/hurricane_stormsurge.swf
Arman Alluwie TP2 SHSS
7+
Indonesia/Australia
Peru,South America
Droughts Heavy Rains
Arman Alluwie TP2 SHSS
8+
Indonesia/Australia
Peru,South America
Heavy Rain Droughts
Arman Alluwie TP2 SHSS
9+Human causes of floods:Clearing of forests Title
Legend
Arman Alluwie TP2 SHSS
10+Feedback
Reducing Impact of Climate Change Pg 125 Not important
Answers to Worksheet 8.1 Student Handout
Arman Alluwie TP2 SHSS
11+
Natural Hazards
Floods Droughts
Causes Natural causesEg. Excessive rainfall
Natural causesEg. Delayed or insufficient rainfall
Human causesEg. Clearing of forests
Human causesEg. Reduced forest cover
Impact on people and the
environment
Eg. Loss of lives Eg. Shortage of water and food
How people have adapted to floods
and droughts
Eg. Building artificial levees or dykes
Eg. Management of watershd and agricultural practices
pg. 138- 147 of textbook
Today
Arman Alluwie TP2 SHSS
12+Impacts of Floods:Fertile Soil / Loss of Lives Provides fertile alluvium
Floodplains around coastal areas and rivers attractive places for cultivation of crops/ farming many people continue to live on low-lying plains near
rivers despite risk of floods
BUT when flooding occurs, lots of lives are lost Based on location and predictability Eg. 2003, north-central Huai River Basin
298 lives
positive impact
negative impact
Arman Alluwie TP2 SHSS
13+Impacts of Floods:Damage to Property and Infrastructure Disrupts power supply and phone lines, cutting off
communication Making relief efforts and emergency evacuations
difficult
Arman Alluwie TP2 SHSS
14+Impacts of Floods:Spread of diseases Overcrowded makeshift shelters
Lack of sanitation and clean drinking water Especially in countries where sewage is not piped Floating debris / Dead bodies
Arman Alluwie TP2 SHSS
15+
Arman Alluwie TP2 SHSS
16+Impacts of Floods:Damage to Environment Destroys plant life and natural habitats of animals
eg. Tsunami that struck Java on 17 July 2006 severe damage to the coastal ecology nature reserve near Pangandaran Beach
Arman Alluwie TP2 SHSS
17+Impact of Droughts:Shortage of Water and Food People and animals die from dehydration and
crops destroyed
Especially crops which are dependent on seasonal cycles eg. monsoon rain
Leads to famine
Arman Alluwie TP2 SHSS
18+Impact of Droughts:Forest fires and haze Vegetation becomes very dry and catches fire
easily Note that a drought is defined as “prolonged period
with little or no rainfall” An area may be experiencing drought but still have
vegetation around.
Smoke from forest fires lead to haze in neighboring countries
Affects environment and health of people
Arman Alluwie TP2 SHSS
19+Impacts of Droughts:Damage to the environment Desertification
spread of deserts into areas where there is little or no rain
Arid and Semi- Arid Regions places with 250- 500 mm of rainfall per year
Soil becomes very dry and unable to support vegetation
Soil blown away by wind, leaving a barren piece of land
Deserts around the world are expanding at a rate of about 80 000 square kilometres per year.
(desertification vulnerability)
Arman Alluwie TP2 SHSS
20+Checkpoint 1:Impacts of Floods and Droughts
Floods Droughts
Impact on people and the environment
1. Loss of lives2. Damage to
property and infrastructure
3. Spread of diseases4. Damage to the
environment5. Fertile Soil for
agriculture
1. Shortage of water and food
2. Damage to the environment
3. Forest fires and haze
pg 138- 142
am I able to discuss the impacts of floods and droughts on human lives and the environments?
Arman Alluwie TP2 SHSS
21+Flood Management Strategies:Building artificial levees/ dykes walls of sand, stone and concrete
increases holding capacity of river
BUT must be paired with other strategies Yellow River, China not successful in preventing
floods because of constant deposition of sediment river bed becomes raised, making river shallower water levels rise higher than the dykes higher dykes have to be built constantly
Arman Alluwie TP2 SHSS
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23+Flood Management Strategies:Construction of Dams Control the amount of water flowing into rivers
Gates which hold back or release water from the man-made reservoir behind it reservoir increases holding capacity
Controls the amount of water that flows downstream
BUT slowing down the speed of water increases the accumulation of sediments
not enough energy to carry sediments raise reservoir bed and cause flooding in the future
Arman Alluwie TP2 SHSS
24+Flood Management Strategies:Construction of Dam Three Gorges Damn, Yangtze River
Arman Alluwie TP2 SHSS
2:49- 5:55 of http://www.youtube.com/watch?v=3z9K82ZVdMA
Arman Alluwie TP2 SHSS
25+Flood Management Strategies:Building Control providing information for developers in flood prone
areas
construction of good network of drainage canals eg. flood prone areas in Singapore have dropped from
3200 ha in 1970 to 238 ha in 2006
Arman Alluwie TP2 SHSS
26+
Arman Alluwie TP2 SHSS
27+
Arman Alluwie TP2 SHSS
28+Flood Management Strategies:Watershed Management Watershed
boundary which is marked by crests of hill rides and mountains
separates on drainage basin from the next
Arman Alluwie TP2 SHSS
29+
Arman Alluwie TP2 SHSS
30+Flood Management Strategies:Watershed Management Eg. Royal Forest Department (RFD) in Thailand
detailed plans on conserving natural vegetation in watersheds
re-planting tress in areas which were previously cut down
reducing surface runoff and amount of sediments
Arman Alluwie TP2 SHSS
31+Flood Management Strategies:Flood Insurance Financial resources to rebuild property if a flood
strikes
Depending on trends and history of floods
eg. UK, national flood insurance programmme helps reduce financial burden
Arman Alluwie TP2 SHSS
32+Flood management strategies:Monitoring and education modern technology allows us to monitor weather
patterns and issue warnings
Educating citizens on what to do in the event of a flood Evacuation plans
Safest route to the nearest food shelter Public announcements
Flood warning signs
Arman Alluwie TP2 SHSS
33+Flood Management Strategies:Post-flood management measures Evacuation plans
boats / helicopter to temporary shelters
Opening public areas for humanitarian and rescue operations Louis Armstrong New Orleans International Airport
during Hurricane Katrina
Foreign Aid in the form of food, water, blankets, medical teams
Arman Alluwie TP2 SHSS
34+Checkpoint 2:Flood Management Strategies
pg 142- 145
am I able to evaluate the effectiveness of management strategies taken to mitigate and respond to floods?
1. Building Artificial Levees/ Dykes
2. Construction of Dams
3. Building Control
4. Watershed Management
5. Flood Insurance
6. Monitoring and Education
7. Post- Flood Management Measures
Arman Alluwie TP2 SHSS
35+Drought Management Strategies:Management of watershed and agricultural practices Agenda 21 Report
Eg. Mongolia hundreds of thousands of seedlings planted to
increase vegetation in drought-affected regions laws to limit the number of trees
only local community allowed to cut down trees for firewood
Arman Alluwie TP2 SHSS
36+Drought Management Strategies:Management of watershed and agricultural practices Growing crops to suit the dry climate of regions
Changing staple diet or importing food
Arman Alluwie TP2 SHSS
37+Drought Management Strategies:Using proper irrigation techniques brings water to areas which receive little or no
rainfall
eg. Turkey, precision sprinklers drip small amounts of water directly onto crops
Arman Alluwie TP2 SHSS
38+Drought Management Strategies:Cloud Seeding induces formation of rain
disperse substances like silver iodide or dry ic
enable water droplets/ ice crystals to form more easily nucleus for water droplets in the air to adhere to
over time clouds form and rain falls
dispersed by aeroplanes or machines on the ground
eg. Thailand, 2005, ease drought by 80% but cost of seeding very high and no guaranteed
success
Arman Alluwie TP2 SHSS
39+Drought management strategies:Post- Drought U.S. Agency for International Development
(USAID) donations of money, food and water to Ethiopia 2006
Food for Hungry Relief brought in water in tanker trucks and used
“dewatering” pumps to transfer the water into school cisterns
Arman Alluwie TP2 SHSS
40+Checkpoint 2:Flood Management Strategies
pg 146- 147
am I able to evaluate the effectiveness of management strategies taken to mitigate and respond to droughts?
1. Management of watershed and agricultural practices
2. Using proper irrigation techniques
3. Cloud seeding
4. Post-drought management measures