20 Superb Facts about Floods

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Updated on: Educator Review By: Michelle Connolly

Floods are the accumulation or collection of a great deal of water that submerges the land. In the sense of flowing water, it can also apply to the flow of tides. Floods often result from heavy rains and may result from the increasing volume of water in a river or lake watercourse, which exceeds levies. As a result, some of the water exceeds its natural limits.

Generally speaking, floods are harmful because they damage properties and may wash away the top layer of soil; rivers and seas overflow on the beaches. The concerned countries must predict this situation by abandoning those areas and building water dams after the flood. However, the size of a lake or other water body will vary according to changes in seasonal rains and snow melting. It is only significant if the flood targets wild areas that threaten the lands in which it resides.

Floods provide fertile soil on both sides of rivers, provide fish with plankton food, and help fill rivers by gathering water, removing ecosystem waste from the riverbed, and feeding groundwater reservoirs. These natural phenomena occur beyond the control of humans, just as earthquakes, volcanoes, and tsunamis, which result from an increase in the water level in any river, sea, or ocean due to the rise in the amount of rain.

It starts with rain and snow, specifically melted water, the primary water source on earth. Quantities of water are lost in seepage processes in the ground or through evaporation or absorption, and the remaining amount serves to feed the rivers with the necessary moisture.

Floods are one of the common types of natural disasters, and they occur when an excess of water floods ordinarily dry land. Floods usually result from heavy rainfall, rapid snow melt, or storm surge caused by a tropical cyclone or tsunami in coastal areas.

Floods can cause widespread destruction, resulting in loss of life and damage to personal property and essential public health infrastructure. From 1998 to 2017, floods affected more than two billion people worldwide. People who live in floodplains, buildings that are not flood-proof, or those who lack flood warning and awareness systems are most at risk of flooding.

Between 80 and 90% of all documented disasters caused by natural hazards over the past ten years were caused by floods, droughts, tropical cyclones, extreme heat waves and storm surges. The frequency and intensity of floods are also increasing, and heavy rains are expected to continue to be frequent and intense due to climate change.

How does a flood occur?

A flood occurs when the water rises and covers a normally dry area. Most floods take several hours or even days to develop, which gives residents enough time to prepare or evacuate, while some floods occur suddenly and without warning, and this type of flood can be hazardous.

Floods can turn a running stream into a massive wall of water that sweeps through and destroys everything in its path in one moment, and many factors cause floods. Hurricanes, rain and sewage blockages are among the most common elements in the occurrence of floods in different regions around the world, and here are some of the main reasons for the occurrence of floods:

1.      Rains

Rain is the main factor in most cases of floods in the world, as the high intensity of rain over a long period leads to the flow of water across the land, contributing to the occurrence of floods. Floods can occur during a short period of rainfall depending on the distribution and quantity of rain and the extent of soil moisture. The force of rainwater can also erode and weaken the foundations of buildings, causing collapses and cracks.

2.      Dams Collapse

A dam is an engineering structure that keeps water from flowing, and the potential energy stored in it is used to generate electricity. Sometimes the dam walls can become weak and prone to collapse due to their inability to absorb more water.

So, the dam’s collapse can cause widespread flooding in the range in its vicinity. Usually, flooding occurs when dams are built on both sides of the river to prevent water flow into neighbouring lands and solve this. Excess water is deliberately released from the dam to prevent it from collapsing and thus causing floods.

3.      Global Warming

Global warming can be defined as the unusually rapid increase in the earth’s average surface temperature over the past century due to greenhouse gases released by burning fossil fuels. Global warming is one of the leading causes of floods.

When temperatures rise, precipitation becomes less frequent, and the air carries more moisture, which leads to drought. Still, at some point, the sky liberates the humidity in the air through weighty rains, so floods occur because the earth cannot absorb the large amounts of water that fall.

4.      Melting glaciers and mountain tops

Ice and snow accumulate in cold regions during the winter, and when the temperature rises in the summer, snow and ice melt, leading to large movements of water to dry land. Flood thaw in this type of flood.

5.      River flood

It occurs when the water level increases so that it overflows towards the land areas on both river banks. This type of flood occurs when the water accumulates more than usual at the top of the river (its source). Since the water flows downstream, which is lower, it rushes suddenly in a considerable amount. Hence, the river level rises above average, and floods occur.

6.      Strong winds in coastal areas

Strong winds and hurricanes may carry sea water towards dry coastal lands, leading to flooding. Sometimes the winds may also have rainwater with them, causing intense floods, and at other times sea water overflows in coastal areas due to the tsunami phenomenon.

Flood Types

Floods are divided into five main types, which are as follows:

1.      Coastal flooding

Strong winds and other extreme weather, along with high tides, can cause sea levels to rise more than expected, forcing water to reach beaches and causing flooding.

2.      River floods

River flooding occurs due to a higher water level than its natural levels, which forces the water to reach the areas surrounding the river, causing a flood. Heavy rains, melting snow and closing of the riverbed due to any obstruction, such as waste, cause rivers to overflow.

3.      Sudden floods

A flash flood usually occurs due to heavy rains, as it may sometimes occur due to a defect in the water barriers or the sewage system, and flash floods are fast-moving and unexpected.

4.      Groundwater floods

Groundwater flooding occurs due to the groundwater level rising above its natural levels, which forces the water in the ground to reach the earth’s surface. This type of flooding is often caused by prolonged rainfall.

5.      Sewer floods

Sewage flooding results from a defect in the sewage systems, when the sewage system does not have enough capacity to withdraw water resulting from heavy rainfall or river floods.

Flood damage to the environment

Floods can cause severe consequences for the environment, and among the most prominent environmental damages are the following:

  1. Damage to the vegetation around the flood area.
  2. Loss of many marine animals to their habitat.
  3. Decreased water quality.
  4. Pollution of coastal food resources.
  5. Low coastal production.
  6. Introducing excess sediment and pollutants, such as heavy metals, waste and chemicals, into the flood water source.
  7. Damage to marine production, especially fish production.

Flood damage to Human Life

The occurrence of floods causes significant damage to human life, and the most prominent of these damages are the following:

1.      Loss in human lives and properties

The most significant direct effects of floods are human deaths, property, crops, livestock, infrastructure, and health damage due to diseases carried by flood waters.

2.      Loss of sources of livelihood

In conjunction with the damage to infrastructure facilities such as bridges and roads, economic activity in the areas where the flood occurs will stop, which leads to the disruption of many commercial, agricultural and industrial businesses, and thus the loss of livelihoods for a period that may exceed the period of the flood occurrence.

3.      Low productivity and purchasing power

The damage to the infrastructure will last for a long time, leading to a decline in productivity and purchasing power and a decrease in the price of floodplain lands.

4.      Mass migration

The recurrence of floods that affect livelihoods may lead to the migration of people from flood-inflicted areas to urban areas, leading to increased poverty in the outskirts of cities, where the displaced population often resorts.

5.      Psychosocial side effects

The human damage caused by the floods causes the victims’ families to suffer long-term adverse psychological effects due to the loss of their loved ones, the displacement of individuals from their homes, and the failure of their properties and jobs, leading to their humiliation from challenging psychological pressures.

6.      Obstruction of development programs

The occurrence of devastating floods impedes human, economic and other development. Some recurring floods may stop economic movement, affecting investment and the labour force’s availability due to their emigration.

Flood Prevention Methods

A person cannot stop rain from falling or prevent water from overflowing on the banks of rivers, as these are natural phenomena. Still, authorities can undertake several measures to mitigate the effects of these phenomena:

1.      Marine firewalls

Sea walls and tidal gates were built in some areas in order to repel waves and rising water levels and thus prevent water from reaching the beaches when it overflows from its average level. In other regions, sandbags prevent floods after collecting and stacking strategically. 

After the last tsunami that hit the shores of Japan in 2011, the Japanese government decided to construct a series of concrete sea walls that extend over a distance of about 400 km and will be at a height equivalent to five residential floors. In some areas, to prevent future disasters from tsunamis on the country’s northeastern coast.

2.      Water gathering

In some areas, retaining walls, artificial lakes, dams, water reservoirs, or basins are constructed to collect rainwater and avoid its accumulation in an amount sufficient to flow onto the surface of the earth.

3.      Urban planning

Construction companies need to obtain permits before constructing new buildings in order to ensure that the waterways are not blocked by their facilities. Also, sewage networks must be covered and free from any obstacles blocking or impeding their work. This way, water can quickly run through it when it rains, reducing the chances of floods in cities.

4.      Vegetation

Trees, shrubs, and grasses help protect the land from erosion when water flows over it quickly, as it prevents dust from being washed away with it. Therefore residents of low-lying areas should be encouraged to plant many trees to help break the moving force of flood waters and preserve the integrity of the soil.

5.      Raising Awareness

Sewer networks are clogged in many developing countries due to the dumping of rubbish. People need to learn more about the effects of these behaviours when it rains. When it rains, the waterways and canals are clogged with vast pieces of rubbish and rubble, so they fill up quickly, and the water finds its way to the streets and people’s homes. Therefore, awareness is fundamental, and the media must warn people of the dangers of floods and what can be done to reduce their impact.

6.      Water collection basins

They are small reservoirs built and connected to the waterways. They provide temporary storage sites for flood water, which means that when floods occur, the water will collect in the basins, giving residents more time to evacuate their homes and belongings.

World’s Massive Floods

In 2007, the United Nations recorded about 70 severe floods, including floods in Sudan, Ethiopia, Myanmar, the Philippines, Vietnam, Indonesia, China, India, Bangladesh, Nepal, Pakistan, Afghanistan and Colombia.

1.      Flooding of the Yangtze and Huaihe Rivers 1931

The flood of the Yangtze and Huaihe occurred from July to November 1931 in China, where the country suffered from terrible drought conditions during the years preceding the disaster. In the middle of 1931, several changes occurred in heavy snow and rain showers.

In addition to the nine Hurricanes during these months, the rivers retained more water than usual, so the Yangtze River flood occurred first. The Huaihe flood soon followed, and the flood waters reached Nanjing, the capital of China at the time, and caused drowning and infection of many people with waterborne diseases. It is estimated that The number of victims ranged from one to four million.

2.      Yellow River flood in 1887

The Yellow River flood occurred in China in 1887 and caused the deaths of approximately 900,000 to 2,000,000 people. Heavy rains caused the river water to rise above the barriers intended to protect the local population, which displaced nearly two million people and killed about 900,000 people.

3.      Yellow River flood in 1938

The Yellow River flood occurred in China in 1938. It was a deliberate act during the China-Japan war by order of Commander Chiang Kai-shek, who ordered the destruction of the dam system in the river, which led to a wave of flood waters that quickly spread throughout the country.

It caused the deaths of approximately 500,000 to 800,000 people, and four million people were forced to leave their homes, and it was not possible to curb and contain the flood except in 1947, that is, years after the defeat of the Japanese.

4.      Banqiao Dam flood1975

The Banqiao Dam flood occurred in 1975 in western Hainan Province in China due to the collapse of the Banqiao Dam due to the tropical cyclone that happened. This flood caused more than 150,000 victims, making it one of the most significant disasters caused by hurricanes.

5.      Yangtze River flood 1935

The Yangtze River, the longest river in Asia, caused nearly three-quarters of the floods in China due to the heavy rains that occurred in July. The river flood in 1935 killed about 145,000 people, and many were displaced. Others suffered from starvation, dehydration, and disease.

6.      Yenisei River

It is classified among the longest rivers in the world, with a length of five thousand five hundred km. In terms of basin area, it ranks seventh in the world, amounting to the equivalent of two and a half million square km and takes its waters from the heights of Mongolia, and pours its waters into the Arctic Ocean.

It floods twice yearly; the first occurs in spring due to ice melting, and the second is in summer or autumn due to heavy rain. Its water freezes in the winter.

7.      Amur River

It ranks fifth in the world in terms of length, reaching two thousand eight hundred km, and its area is one million km2. It is the eleventh in the world in terms of area, and it takes its waters from the highlands of Mongolia, specifically the interior. At the same time, it pours its waters into the Tatar Strait, and its seas overflow in the spring. The melting of ice results from high temperatures, and the second is in the summer or autumn due to heavy rain.


A tsunami is a group of violent hurricanes that arise by moving large areas of water, oceans, towards the earth. It may also result through earthquakes and large and significant activities, whether under or above the water or through the eruption of volcanoes or any explosions under the water’s surface.

In addition to Underwater earthquakes and collapses that occur above the surface of the earth, nuclear weapons explosions in seawater or the impact of comets, and because of this tremendous amount of water and energy resulting from its movement, destructive effects are formed due to it called “tsunamis”.

How is a tsunami formed?

The historian Thucydides was the first to link the phenomenon of earthquakes that occur in the depths of water and describe them to tsunamis. However, the understanding of the nature of tsunamis remained limited until the twentieth century, which is still the focus of some research and studies.

In the ancient texts of geography, geology, and oceanography, the tsunami phenomenon was referred to as marine seismic waves. It witnesses atmospheric storms and high meteorological tension, which result in hurricanes and hurricanes that lead to intense storms in which the water is several meters higher than the level of the known tidal phenomenon.

The reasons mentioned above that were mentioned led to a decrease in atmospheric pressure in that tense region. When this storm approached the shore, it led to the sinking of large land areas; storms flooded Myanmar and Burma in May of 2008.

Tsunami warnings and prevention

It is impossible to predict the tsunami phenomenon or try to prevent its occurrence accurately, even if the seismic indicators point to its correct location. Oceanographers, geologists, and seismologists analyse that each earthquake has several factors that differ from each other.

Despite that, some warning signs may warn of the occurrence of a tsunami in order to try to limit its damage through the use of some advanced devices to monitor tsunamis, such as sensors that operate by pressure, which monitor and monitor the pressure of the water column, and that is through specific calculations.

Scientists also believe that some animals can sense the waves emanating from earthquakes, volcanoes (tsunamis) and various natural phenomena by observing animals; these animals are elephants.

Fukushima Tsunami

American scientists discovered the presence of radioactive tuna fish near the coast of California from Japan. After examining it, they found that it was infected with radiation due to the polluted ocean after the nuclear reactor accident in the Fukushima region in 2011 due to the tsunami. Much waste continues coming from Japan, which is 90,700 km from California.

To sum up, many natural phenomena occur beyond the control of humans, including earthquakes, volcanoes, and floods, which are natural phenomena that result from an increase in the water level in any river, sea, or ocean due to the rise in the amount of rain.

To learn about several natural phenomena, you can read about Natural Disasters, Endangered Animals, and Stones.

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