floods part 2

Question 1

What are some of the cities that are prone to floods?

Answer 1

Dhaka, Bangladesh
-Located in the paths of seasonal winds which bring intense rainfall
New Orleans,United States of america
-Located in the paths of hurricanes
Calgary, Canada
-Location on mountain foothills causes floods from snowmelt
Tacloban, Phillipines
-Location along coast makes in more prone to storm surges and floods
Newport, United Kingdom
-Prone to floods causes by storm surges

Question 2

What are the reasons behind why some cities are more prone to floods than other floods?

Answer 2

Height of land above sea level
Proximity to water bodies
Permeability of surface cover
Channel capacity.

Question 3

Elaborate on ¨Height of Land above sea level¨

Answer 3

● The height of land above sea level affects the likelihood that a place would
flood

● Cities that are located on low-lying lands are more prone to floods
● Example: Some Dutch cities (e.g. Amsterdam) are prone to floods because
they lie several metres below sea level

Question 4

What does sea level refer to?

Answer 4

Sea level generally refers to the mean sea level.

The mean sea level is the average height of the sea surface at a given site over a long period of time.

Question 5

Elaborate on ¨Proximity to water bodies¨

Answer 5

● Water bodies are significant accumulations of water
○ Oceans
○ Seas
○ Lakes
○ Rivers
○ Reservoirs
● Cities which are located near water bodies, such as coastal cities or cities with
a river running through them, are more prone to floods
○ Example: Manila, Philippines
■ Manila’s proximity to the Pasig River makes it more prone to
river floods as compared to other cities which are further away
■ Manila lies at the mouth of the Pasig River
■ The Pasig River flows through the centre of Manila and
connects Laguna de Bay to Manila Bay
■ Manila’s proximity to the Pasig River makes it more prone to
river floods as compared to other cities which are further away

Question 6

Elaborate on ¨Pemearability of surface cover¨

Answer 6

● Permeability refers to the ease with which water can infiltrate or seep into
the ground.
● Cities with a higher proportion of concrete (impermeable) surfaces might be
more prone to floods.

Question 7

What are vegetated surfaces?

Answer 7

Vegetated are more permeable than concrete surfaces.
vegetated surfaces allow water to infiltrate the ground easily, allows lesser surface runoff and lower likelihood of floods

Question 8

What are concrete surfaces?

Answer 8

Concrete surfaces are impermeable and does not allow water to infiltrate the ground. Concrete surfaces increases the likelihood of floods and high surface runoff

Question 9

Elaborate on channel capacity.

Answer 9

● Channel capacity refers to the volume of water that can be held in the
channel of a river or canal without overflowing.
● Floods may occur when there is too much rain and the capacity of the
channel is exceeded
○ AYE flood in September 2013 due to the Sungei Pandan Kechil drain
● Why a city needs a good network of canals and drains:
○ A city tends to have a high proportion of built-up areas with concrete
surfaces, resulting in large amounts of surface runoff during a rain
event.
○ A network of canals and rivers is thus needed to help the city drain
water away quickly.
○ When the canals and rivers are unable to cope with the high surface
runoff, a flood will occur.