2. Cities more prone to floods

Use Google Earth and explore these cities to find out more on why they are more prone to floods.

Factors that cause cities to be more prone to floods

(I) Height of land above sea level

· Cities that are located on low-lying lands are more prone to floods because even a little rise in sea level will cause these cities to experience flooding.

(II) Proximity to water bodies

· Cities located near water bodies are more prone to floods because these cities would experience flooding whenever water overflow the banks of these water bodies.

(III) Permeability of surface cover

· Permeability refers to how easy water can infiltrate into the ground.

· As concrete surfaces are almost impermeable, water cannot infiltrate the ground. This leads to a higher surface run-off and eventually a higher likelihood of floods.

· As vegetated surfaces are more permeable, water can infiltrate the ground easily. This leads to less surface run-off, thereby lowering the likelihood of floods.

(IV) Channel capacity

· Floods may occur when the amount of rain exceed the capacity of the channel.

· In cities with a high proportion of built-up areas and concrete surfaces, it is likely to experience large amounts of surface runoff during a rain event. Canals may not have the capacity to carry this runoff away fast enough, thereby leading to floods.