We explain what floods are and the causes and consequences they present. Also, what are its characteristics, types and examples.
Floods can have a human and material cost.
What are floods?
Flooding is the overflow or accumulation of water in an area that is normally dry. Floods are a multi-causal phenomenonwhich means that they can be produced by many causes combined with each other.
When floods occur, Water can cover large areas of land and affect people, animals, infrastructure, homes and crops.They can also cause landslides and damage roads and bridges.
When floods occur in urban areas, they often cause costly property damage and often lead to human deaths.
Causes of floods
Floods can be caused by rivers and lakes overflowing.
The causes of flooding can be natural or human. Among the natural ones the most important are:
- Excess rainFlooding can occur after several days of rain. In these cases, the precipitated water is greater than the absorption capacity of the soil or urban water systems and therefore accumulates on the surface.
- Overflow of rivers and lakes. Floods may occur as a result of the growth in the height of rivers and lakes, due to intense rain in the area or in other areas of its basin. They can also occur as a consequence of the melting of ice in river sources.
The most important human causes are:
- The expansion of cities. The growth of urban areas makes the soil waterproof and reduces its absorption capacity. Furthermore, urban settlements often occupy naturally flooded areas such as river or stream valleys.
- The waterproofing of the floors. The construction of new neighborhoods or the expansion of the agricultural frontier causes soils to become compacted and impermeable. When it rains, their absorption capacity is much lower and this can aggravate the effects of flooding.
- Artificial modifications of the terrain. Sometimes, to prevent flooding, land is raised (embanked) to prevent flooding. This has a positive effect on the raised land, but it greatly increases the risk of flooding on nearby land that was not raised.
- The inefficiency of flood control works. Cities that have flooding problems usually build hydraulic works to reduce their effects. Sometimes it happens that these works are not built correctly, or were built many years ago and are obsolete.
- The breaking of dams or dikesWhen one of these structures breaks, it usually causes a flash flood as all the water contained in the reservoir is quickly released.
Being a multi-causal phenomenon, floods are never explained by a single cause, but are produced by the combination of several of them. For example, sometimes floods occur not only because it rains a lot or a stream overflows but also because there are hydraulic works that are not built or are obsolete, or because the ground was waterproofed due to the expansion of a city.
Consequences of flooding
The consequences of floods vary according to their intensity and duration. Some of them are:
- The destruction of crops and harvests. Floods can have significant economic impacts on rural producers due to the loss of crops that are ruined by excess water.
- The destruction of transportation routes. Flooding can inundate roads and destroy bridges and other transportation infrastructure.
- The destruction of homesFloods can damage or destroy homes. In the case of the most precarious homes, floodwaters can often sweep them away and destroy them completely.
- Loss of human life and damage to health. Floods can be deadly, causing serious injuries, illness and psychological problems such as stress, depression and anxiety.
- The interruption of public services. Floods often cause disruption of electricity, drinking water supply and transportation services.
- Population displacement. Floods can force people to leave their homes or communities and migrate to another city.
Types of floods
Floods are often caused by excessive rainfall.
Floods can be classified according to their origin and characteristics:
- River floodsThey are caused by rivers overflowing due to heavy rains or the melting of snow at their source. These floods can last for several days or even weeks.
- Pluvial floods. They are caused by intense and prolonged rains, which means that water cannot be absorbed by the soil and accumulates on the surface.
- Coastal floodingThey are caused by rising sea levels. They can also be caused by natural phenomena such as hurricanes, typhoons and cyclones.
- Floods due to breach of dams or reservoirsThey are caused by the failure or collapse of dams or reservoirs, resulting in the sudden release of large amounts of water.
Differences with flooding
Flooding occurs due to the saturation of soils and the accumulation of water on a piece of land.. Saturated soil means that it can no longer absorb more water, so all the excess that accumulates when the soil is saturated will remain on the surface and will not be infiltrated into the soil.
When it stops raining, flooding usually takes many hours to disappear. The absorption capacity of soils usually recovers slowly, so Flooded land may still have water on the surface even several days later. after the end of the event that flooded them.
Soils can also become waterlogged without precipitation. Sometimes groundwater layers rise to the surface and flood the soil without any river overflow or intense precipitation.
Flood prediction
Satellite images help predict storms that can cause flooding.
There are numerous tools that can help predict flooding ahead of time. One of them is monitoring rivers and streams that allow measuring flow and height in real time. In the event of an unusual modification of some of the hydrological parameters, the authorities are notified so that they can take preventive measures.
Also the meteorological services of each country use Satellite information to predict the arrival of storms or extreme weather events that could cause flooding.
Science also contributes to the prediction of floods through simulation models that allow for the prediction of the water behaviour of a region in the event of a storm or a river flooding. This information allows authorities to make decisions in the face of these types of phenomena.
How to prevent floods?
Since ancient times, water defences such as reservoirs, barriers, walls or drainage systems have been erected to protect cities from rising sea levels or river floods.
In cities, adequate urban planning is essential that includes the construction of adequate infrastructure for flood control and green spaces to promote water infiltration.
Waste management is also important as a flood prevention policy. Floods often occur because drainage systems are clogged with rubbish, which slows down the drainage of water. For this reason, it is essential to maintain drainage systems and ensure they are clean.
Restoration and conservation of wetlands, rivers and mangroves can help prevent flooding, as these ecosystems function as natural sponges that retain and absorb water.
State regulation of urban development is also essential to prevent flooding. Authorities must ensure that new buildings and neighbourhoods are located in safe areas and meet all drainage standards suitable for them and their neighbours.
Flash flood or flash flood
The flash flood They are associated with heavy rains in mountainous regions.
A flash flood (Spanish: flash flood) is a type of flash flood that occurs in a short period of time, usually within minutes or hours. These floods occur as a result of heavy rains that precipitate a large amount of water in a short period of time.
The flash floods They are especially dangerous due to their speed and intensity, and can occur anywhere, but are most common in mountainous areas, canyons, and streams. Because they occur with little or no warning, they are very difficult to predict and can be very deadly.
One of the characteristics of the flash floods is that they can displace large amounts of sediment and other materials, which further increases their danger. In addition, Strong water currents can sweep away vehicles, animals and people.and cause significant damage to infrastructure such as bridges and roads.
Floods of history
Some of the great floods in history were:
- The Mississippi River FloodIt happened in the United States in 1927. It flooded several states and left more than 400 dead.
- The flooding of the Yellow River. It happened in China in 1931. It covered more than 150,000 square kilometers and it is estimated that more than 2 million people died.
- The Yangtze River flood. It happened in China in 1954. It affected more than 180,000 square kilometers and caused more than 30,000 deaths.
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