Floods » What is it, Characteristics, Concepts
Floods
What are floods?
Floods are partial or total water occupations that occur on a surface that is usually dry and that could cause material and / or human damage.
Floods are events produced by natural phenomena such as rain, hurricanes or melting snow; or produced by human activity.
Types of floods
There are various classifications of floods according to the various official disaster prevention agencies. This is a compilation of all the categories:
Flash floods ( flash floods )
These are events in which water accumulates and saturates the ground in a very short period of time. Generally they are floods caused by precipitations of sudden appearance but of intense effect. That is, rains that are generated suddenly and also last a long time.
Flash floods are considered one of the most dangerous categories, since by their nature they make prevention and eviction tasks difficult for the affected populations.
One of the most outstanding characteristics of flash floods is that they tend to be generated on terrain with steep slopes. This facilitates the rapid descent of the water and the flooding of the land, with the structural and human damage that this implies.
Slow floods
They are generated by persistent rains that can be intense or moderate, which causes a progressive saturation of the land. In these cases, rainfall can last for at least two to four days.
The persistent nature of rainfall can cause material damage to poor structures, as well as damage crops and crops. However, in this case it is possible to activate damage prevention and containment protocols because the time frame is longer.
River floods
The overflowing of rivers is one of the most common causes of recurrent flooding in third world regions.
They are floods caused by the overflowing of rivers, either due to problems associated with the quality of the land on their banks or due to a considerable increase in flow.
This rise in the water level can be caused by heavy or prolonged rains, or by melting snow in areas near the river.
Storm flooding
Satellite view of the Ayatthaya region before and after the monsoon floods in Thailand in 2001.
It is any saturation of the land caused by rain. In some countries, floods of pluvial origin are a constant in certain periods of the year, as in India, whose rains caused by monsoon winds generate large floods during the summer.
Coastal flooding
If barrier floods go over sloping terrain, a flash flood or flash flood can occur .
These are events caused by the rise of the sea, which ends up entering the mainland, either due to the effect of heavy rains, tidal waves, tsunamis, storms or typhoons. In this sense, coastal flooding can occur in one of three ways:
- Direct : the water directly breaks the ground in the absence of natural or artificial barriers.
- Barrier rupture : water breaks a natural or artificial barrier as a result of strong waves.
- Excess barrier : the size of the wave or tide exceeds a barrier, either natural or artificial, and floods the land.
Urban floods
The accumulation of waste is one of the causes of floods in urban areas.
They are a type of flood that affects urbanized cities and communities. They can have a natural origin (rainfall or overflowing rivers) or artificial (failures in hydraulic works, breakdown of dikes, etc.).
Population density, soil erosion, and increased garbage production are just some of the factors that cause urban flooding.
You may be interested in reading: Natural disasters.
Causes of floods
Floods can have several causes. These are the events or activities that can produce floods:
Natural causes
They have to do with natural events that occur without human intervention, such as:
- Rains : they generate a saturation of water in the land that by not draining quickly, cause floods.
- Thaw : the condensation of the ice causes the water to reach the rivers and increase their channel, causing them to overflow.
- Storms, hurricanes, typhoons or tsunamis : they generate waves of great magnitude that can knock down natural or artificial barriers, facilitating the entry of water on land at high speed, and flooding everything in their path.
Unnatural causes
They are factors related to human activities that have a direct impact on bodies of water or on the decrease in the quality of the land. Some of those activities are:
- Hydraulic failures : ruptures of dams or dikes, which release a large amount of water in a very short time, saturating the land or nearby bodies of water and causing flooding.
- Water pollution: solid waste and sewage can obstruct the channels of water bodies, causing their elevation and subsequent overflow.
- Erosion of the land : urban works, excessive cultivation or contamination decrease the quality of the land, increasing its permeability, which makes it susceptible to saturation more quickly.
Consequences of floods
Floods have an impact on multiple levels, and end up affecting not only the environment but also local and national economies.
Environmental consequences
Floods can generate slight, moderate or severe modifications in the affected topography. These changes in the terrain can be part of natural dynamics (such as monsoon rains) or human activity, and can affect local ecosystems.
If a crop is washed away by a flood, the ecosystem of which it was a part is also altered. Pollinating agents (such as bees) and animals that benefited from crops to feed themselves, can move to other areas and negatively alter that new place.
Economic consequences
Floods can cause considerable structural damage, affecting homes, commercial premises, and crops. All this has a negative impact on the local economy, which in turn deteriorates the living conditions of the affected people.
In 2017, monsoon rains flooded the tea crops of Darjeeling, India. The loss of the harvest had an impact on the Indian economy and increased the value of Indian tea worldwide, hurting the end consumers.
Social consequences
In the most serious cases, floods can cause human loss or serious injuries. Furthermore, this type of event can induce forced population displacements, as a way of solving the loss of housing or a source of work.
It is also possible that the authorities order the suspension of educational, work or recreational activities, which directly impacts the quality of life of people.
Health consequences
Floods can generate foci of diseases such as dengue, infectious, dermatological diseases, digestive disorders, etc.
In the most disadvantaged areas, these types of situations worsen the already precarious conditions of the local health systems, by collapsing their care capacity.
Examples of floods in Latin America
In Latin America there are several examples that illustrate the magnitude that a flood can reach, especially when adequate prevention or containment measures are not taken.
These are just some of the most relevant events that have occurred in recent history:
Vargas Tragedy, 1999 (Venezuela)
During the month of December, the intense and prolonged rains that occurred throughout the country generated an unprecedented landslide in Vargas state. This situation left a balance of more than 300 thousand victims, thousands of deaths, wounded and missing, in addition to irreparable structural damage.
Santa Fe Flood, 2003 (Argentina)
A persistent and intense rain that occurred at the end of May in the city of Santa Fe and nearby towns, generated a flood of the Salado River. The water managed to penetrate the defenses (which were not finished) and entered the city, causing human and material losses.
Tabasco flood, 2007 (Mexico)
A series of continuous rainfall accelerated the rise of the Usumacinta and Grijalva rivers, flooding 80% of the state of Tabasco.
The dikes and barriers were surpassed by the waters, which brought with it the collapse of the drinking water, electricity and health services, as well as human losses and victims.
Tragedy of Mariana, 2015 (Brazil)
During the month of November, a dam built to retain toxic waste in the city of Mariana, in the state of Minas Gerais, had a leak. A few hours later, the dam gave way and expelled contaminated sludge that reached the Doce River, which supplied drinking water to the entire state.
This situation caused not only the overflowing of the river and the flooding of nearby towns. It also caused irreparable damage to the drinking water system, since it is now unfit for consumption.
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