Chong Boon Secondary School

Sec 2 Geography

FloodsUnit 5 Lesson 1

Types of floods

Inquiry Question

How can cities prepare for

floods?

Thinking Frame

What are floods?

How do floods affect people in

cities?

How should cities prepare

for floods?

How should cities prepare

for floods?

Flood intervention

What are floods

• Sudden increase in surface water.

• Drainage system unable to cope.

• Large amounts of water pooling on the surface.

Floods

• Can bring positive impacts

–Farmers farm on floodbanks

–Benefit from the river sediment that collects after flooding

• Cities tend to face higher flood risk.

Types of flood

1. Coastal Flood

2. River Flood

3. Flash Flood

Coastal Flood

• Occurs along the coast.

–Low-lying coastal areas (river mouths)

• River mouths are where the river discharges into the sea.

• Caused by intense storms

–Tropical storms and cyclones

• Cyclones are also known as Hurricanes / Typhoons

Coastal Flood

• Strong winds generate large waves –Storm Surge

• Storm surges bring higher water levels and cause coastal floods

• Tsunamis also cause coastal floods.

Coastal Flood

River Floods• Sudden increase in river’s flow

(water)

• Water overflows the banks

• Tends to occur on floodplains, lower course of the river.

• Leads to deposit of sediments on floodplains

• Caused by snowmelt, heavy rainfall, dam failure, etc.

River floods

Positive effect of river floods

• Sediments are rich in nutrients.

• Floodplains are good for crop cultivation.

–Wet rice cultivation

• High risk of crop failure when there is sudden flooding.

Floodplain Farming

Flash Floods

• Sudden floods, lasts for a short duration.

• Caused by sudden and heavy rainfall.

• Can also be caused by Coastal and River floods.

• Cities tend to be badly affected by flash floods.

Flash Flood

Summary

• What is a flood?

• What are the 3 main types of floods?

• Which type of flood will affect Singapore the most?

“Oh My Flooded Home!”

Group Work

In your groups,

• Take a look at the map and the scenarios that you have been given.

• Discuss & Identify the type of flood that each scenario is experiencing.

• Answer the questions on the A3 paper provided.

Resident in Town A

“The sky went dark suddenly and the rain was incredible. I’ve never seen rain like that, so

intense and so heavy. It lasted for at least an hour! Then the drains were overflowing. Within

20 minutes, the water was ankle deep and another 10 minutes later it was already knee

deep at some parts of the city”

Resident in Town B

“It’s always like this during this time of the year. It’s the monsoons, they bring the tropical

thunderstorms. Some crazy people still insist on going out to sea for surfing! The storm surge is normally not so bad but this year it stretched

right into the middle of town!

All the subway services were stopped, there was water flooding in the tunnels!”

Resident in Town C

“Whenever it is spring, the snow on the mountain top will melt. There is always this

sudden rush of water from the mountains. Some years the water level rises and just overflows the

banks into the floodplains but this year it was really bad.

A lot of the crops that were planted on the floodplains were swept away by the strong

floodwaters. “

Town AWhat type of flood was

experienced?

List 3 evidences that you found to justify your choice.

You are the mayor of the town. What are 3 things that you can do

to help the people in this Town?

Town BWhat type of flood was

experienced?

List 3 evidences that you found to justify your choice.

You are the mayor of the town. What are 3 things that you can do

to help the people in this Town?

Town CWhat type of flood was

experienced?

List 3 evidences that you found to justify your choice.

You are the mayor of the town. What are 3 things that you can do

to help the people in this Town?

Map of Taman BuayaMount Crocodile

Town C

Town B

Town A

Pacific Ocean