Why does flooding occur?

Answer 1

Firstly, it occurs due to heavy rain and storms during the monsoon season that leaves a lot of rainwater behind on land. This may in turn cause flash floods, where floods move at great speeds, causing destruction and casualties. This is partly because there is too much rainwater to be drained out of the area using pipes and partly because of the height of the land above sea level. For example if the piece of land is below sea level, it would be greatly affected whereas those above sea level would not encounter the same situation as the water from the land will flow downwards either to a lower piece of land or a water body. Poor sewage/drainage systems may also contribute to flooding. Secondly, it occurs due to natural disasters such as cyclones and hurricanes when they sweep across the sea or ocean, bringing a lot of water with them and as they touch land, the water is washed onto land by its powerful high-speed winds. A tsunami may also cause floods by washing seawater onto land when its storey-high waves reaches land. Earthquakes can also contribute in a way that it blocks the movement of a river, clogging up the river and causing an overflow of water in the river, flooding the lands near it. Melting of snow may also be another reason, as when the snow thaws after winter, the water might not be drained off or evaporated that quickly. Lastly, global warming may be another cause of floods. Due to global warming, sea levels are rising as the ice caps at the north and south poles are melting significantly. Sea levels are increasing at an alarming rate of 20+mm/year! If this continues, many more islands and lands below sea level such as Netherlands and Bangladesh may vanish under the seas forever. Currently, more than 30 small islands have been covered totally by seawater. These islands are usually small islands "stranded" in the middle of the oceans or seas, making them vulnerable to the situation. Others are submerged under sea levels due to the effects/aftermath of tsunamis.

Answer 2

Reducing the ozone layer is one of the things that causes the Earth to heat up. Heating melts the ice caps at the north and South Poles, thus putting more water in the sea, thus raising sea level and causing coastal flooding.

Reducing ozone does not warm up the Earth, but increasing other greenhouse gases does.

Ozone is a greehouse gas. It allows UV-A, visible light, and near infrared to pass, but blocks far infrared. When the ozone hole is large, it has been observed that the amount of ice at the Antarctic increases. So if ozone increases, it would follow that the poles would be kept warmer...