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How Flooding Works, And What Causes It

Image obtained with thanks from U.S. Geological Survey.

A flood is a disaster which may or may not be natural which usually entails excessive accumulation of water in a given area. A flood is natural if it is caused by heavy rain, for example, and an unnatural flood is caused by events such as damaged dams or other water storage mediums. A flood can be caused by both natural and unnatural factors such as clogged storm drains (unnatural) and heavy rain.

A flooded neighbourhood.
Image obtained with thanks from U.S. Geological Survey.

Floods are very concerning because they have the potential to wash away homes, people, all other personal property and destroy other infrastructure such as roads, floating debris could damage pipelines, etc.

Floods can be caused by a variety of problems such as dam failures, blocked storm drains due to inappropriate garbage disposal (littering) or damage, torrential (very heavy) rain caused by thunderstorms and hurricanes, as well as storm surge caused by hurricanes, overflowing rivers, and damaged levees (devices which hold back water).


Economic Impact of Flooding

One of the most significant economic effects of flood is property damage. When I say property damage, I am referring to not only destroyed buildings, but also destroyed crops and farms, temporarily affecting food supply. Example: Floods cost the United States an average of $8.17 billion USD per year (30-year average) [Source]. That is more than the hurricane average minimum of $1.2 billion.


Flooding Contributors

Clogged Storm Drains

Storm drains are openings with or without grilles which are situated either on roads, or by sidewalks on the side of roads to drain away as much rainwater as possible so that it does not accumulate on roads and cause hydroplaning or worse hazards.

Storm drains are sometimes clogged because of the improper disposal of a large amount of solid waste on roads and sidewalks which eventually ends up in the drains, inhibiting the flow of water into them. Unfortunately, people often don’t consider the fact that garbage has to be cleaned up by people, and those people have to be paid. Apart from that, storm drains are essential to flood prevention and mitigation.


Dam Failure

As the heading implies, dams can cause flooding by breaking, and that causes the massive amount of water that they contain to flood the areas closest to them. There are different types of dam failures. Some are so significant that they suddenly cause an enormous destructive wall of water to slam into buildings and wash them as well as people away. There are also failures which cause a much smaller amount of water to flow out at a time, resulting in more gradual accumulation of water.


High Population Density

Densely populated areas contain more buildings and more pavement per square mile, and pavement as well as buildings are on top of the soil which would normally absorb a significant amount of water, therefore, water flows on top of the pavement and can accumulate because the roads and buildings are not permeable, therefore water cannot pass through them and be absorbed by the soil below them.


Overflowing Rivers

Excessive precipitation caused by tropical storms and thunderstorms can causes rivers to overflow, resulting in flooding.


Storm Surge

Storm surge is caused when tropical storm winds push water onshore, sometimes far enough inland to cause significant flooding and damage to coastal buildings/infrastructure.

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