sec 2 geography unit 5 lesson 2
TRANSCRIPT
Chong Boon Secondary School
Sec 2 Geography
FloodsUnit 5 Lesson 2
Cities prone to floods
Inquiry Question Why are some
areas more prone to floods?
Flood Occurrence 1985-2011
Key reasons for bigger flood risk
• Larger amount of rainfall received.
• Height of land above sea level.
• Presence of flood protection measures.
Heavy Rainfall
• Dhaka, Bangladesh
• Located in monsoon paths
• Seasonal rains (monsoons)
–Intense and prolonged.
• New Orleans, USA
• Along Hurricane belts
–Intense and strong rains.
Snowmelt
• Calgary, Canada
• At the foothills of mountains.
• Spring snowmelt leads to sudden, massive increase in river load.
Storm Surges
•Coastal countries (Philippines)–Storm surges due to weather
–Typhoon Haiyan (Tacloban)
–Massive destruction
Video courtesy of Plan Internationalhttps://www.youtube.com/watch?v=XUZFW54vtDo
Danger of Dam failure
• Rio Largo, Brazil
• Prone to floods due to location near dams
• Risk of dam failure
Height of land above sea level
• Sea level refer to mean sea level
–Average height of the sea at a given site over a period of time.
–Mid point between the mean low tide and mean high tide.
Height of land above sea level
• Cities located on low-lying lands (below sea level) are more prone to floods.
• Amsterdam, Rotterdam, Venice
Proximity to water bodies
• Oceans, seas, lakes, reservoirs.
• Cities near such places run higher risk of flooding.
• Event of sudden increase in water amount in the water bodies lead to immediate flooding.
Pg 167
Permeability of surface cover
• Permeability
–Ease with which water can infiltrate or seep into the ground.
• Vegetated surfaces more permeable
• Concrete surfaces hare impermeable
• Lower permeability leads to higher flood risk.
Channel Capacity
• Volume of water held in the channel of a river without overflowing.
• Sudden increase in water lead to overflowing.
• City’s drainage system needs constant upgrading to increase the capacity.
Pg 169
PUB’s flood response
• Canals deepening and widening
–Rochor Canal and Alexandra Canal
• Construction of additional canals and drains
• Raising road heightsPg 170
What’s protecting Bangkok?
Summary
• Why do some cities flood easily?
• What are some measures Singapore has taken to cope?
“Good or Bad?”
There are 6 factors shown in the sketch below. In your groups,
briefly (in no less than 3 sentences) explain how each factor canaffect (increase / decrease) the area’s flood risk.Answer on the A3 paper provided.
Let’s pick 3 groups to present!