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Why are cities prone to floods? Why are there cities more prone to floods…
Why are cities prone to floods? Why are there cities more prone to floods than others?
Height of land above sea level
Sea level is the mean sea level
The mean sea level is the average height of the sea surface at a given site.
The lower the height of the land above sea level, the higher chance of flooding taking place.
Proximity to water bodies
Areas that are near the water body --> (such as coastal cities or cities with a river running through them) are more prone to floods.
Permeability of surface cover
Define: 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.
Vegetated surface
More permeable: water can infiltrate ground more easily.
Less surface runoff.
Lower likelihood of floods
Concrete surface
Impermeable: Water is unable to infiltrate into the ground.
High surface runoff.
Higher likelihood of floods.
Channel capacity
Floods may occur when there is too much rain and the capacity of the channel is exceeded.
How did the flood happen?
A city tends to have a high proportion of built-up area 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 to drain water away quickly.
When the canals and rivers are unable to cope with the high surface runoff, a flood will occur.
Define: Volume of water that can be held in the channel of a river or canal without overflowing.