Tsunami and floods

Tsunami: Definition

Tsunami, also known as seismic sea wave or tidal wave, is a devastating ocean wave triggered by an undersea earthquake, an offshore or coastal landslide, or a volcanic eruption. This type of wave is sometimes referred to as a tidal wave, although this is a misnomer because the wave has nothing to do with the tides.

Meteotsunamis

A meteotsunami is a large sea wave that reaches a height of 2 metres (about 6 feet). They are milder than seismic tsunamis and are caused by abrupt changes in air pressure, such as those caused by squalls or storm fronts moving through. The difference in pressure causes a collapse in the ocean or lake’s surface, which pushes outward in all directions.

Extraterrestrial tsunamis

Tsunami waves aren’t really restricted to the surface of the Earth. A 2016 study of the Martian landscape, which used pictures and infrared images to explore the arid planet’s northern plains, discovered evidence of two different tsunami episodes that happened many years ago. Comet or asteroid strikes are hypothesised to have triggered these phenomena.

• Seismic waves are ones that produce a single instantaneous vertical wave. However, soon after the initial disturbance, a series of after-water waves are created to restore the water level
• Therefore, the impact of tsunami is way lesser in the ocean as compared to the coastal areas where they cause large-scale devastations
• Although it may look hard to notice high waves in deeper portions of the ocean, caused by the long wavelength and wave height, these waves are easily observable over deep water 
• Tsunamis are most likely to appear near the Pacific ring, particularly along the coast of Japan, Alaska, Philippines, Indonesia, Malaysia, other Southeast Asia Islands, Myanmar, Sri Lanka, India, etc.

Characteristics of Tsunami 

• Tsunami is one of the earth’s most infrequent hazards that can be massively destructive at times
• In deep water, Tsunami’s wavelengths can often go hundred kilometre long, especially Tsunami enters shallow water as its wavelength decreases, however, the period remains unchanged leading to increase in height

• Tsunamis have very little amplitude offshore. It mainly ranges from a few centimetres to more than 30 metres in height

• From the point of origin, it radiates in all different directions and covers the whole ocean

• Tsunamis usually have a series of waves that come with periods ranging from minutes and hours

• The depth of the water decides the speed of the waves in the ocean. The speed is generally high in shallow water when compared to deep water

Floods

Flooding is a natural calamity, and they happen when a large amount of water overflows and submerges normally dry terrain. Heavy rain, quick snowmelt, or a storm surge from a tropical cyclone or tsunami in coastal locations are all common causes of flooding.

• The most common reason for the occurrence of flood is when the water exceeds the carrying capacity of water bodies and water, unfortunately, travels to neighbouring flood-prone plains
• Floods, despite earthquakes, are often foreseeable because they exhibit appropriate warning signals and develop slowly enough for authorities to make judgments. They also tend to happen just at the usual time of year in well-known places or flood-prone zones
• In coastal areas, one major reason for flooding is the storm surge, melting of ice, excessive rainfall for prolonged periods, and presence of eroded material which maximises the chances of soil erosion
• Floods in the South, Southeast countries, East Asian countries, including India, China, and Bangladesh frequently experience floods
• Nearly 40 million hectares of land in India have been recognised as flood-prone, according to the Rashtriya Barh Ayog (National Flood Commission)
• West Bengal, Assam, and Bihar are among India’s flood-prone states.
• Floods are a risk in states such as Uttar Pradesh and Punjab
• In recent years, flash floods have occurred in states like Gujarat, Rajasthan, Haryana, and Punjab

Tsunamis may create significant flooding in coastal locations. A large tsunami might inundate areas many kilometres inland. The waves that impact the shore first, followed by floods inland, can inflict significant infrastructure damage (including houses and roads), land, agriculture, and livestock.

Spread of Floods by Humans

Some of the human activities which majorly contribute to intensifying the chances of floods are indiscriminate deforestation, disturbances along the natural drainage channels, unscientific agricultural practises, colonisation of riverbeds and floodplains, and so on.

Consequence of Floods

One of the most immediate and serious impacts of flood is the loss of life, buildings, and structures like sewerage systems, bridges, canal, and so on. Flood shows hazardous effects on power transmission, power generation, and water supply. 

Negative Impacts of Floods

• One major impact of floods is the frequent deterioration of agricultural land and human settlement
• When water gets into a field, it destroys precious crops as well as infrastructure including trains, roads, bridges, and transportation
• Millions of people have died as a result of floods, and millions more have become homeless. Floods also result in the loss of livestock

Positive Aspect of Floods:

• Floods have a significant favourable impact on agricultural areas, which is beneficial to crops
• Majuli (Assam) is a well-known example of good paddy crops growing in the aftermath of the Brahmaputra River’s yearly floods

Solutions:

• Construction of dams, development of flood protection causeways, particularly in flood-prone areas, forest conservation, and discouragement of construction activities
• Another strategy may be to remove human encroachment from numerous river channels and depopulate the flood basins.

Conclusion 

Tsunami and floods are the two most destructive natural calamities that can occur due to several reasons such as human intervention, earthquakes, volcanic eruptions, and so on. These not only harm the property but take away millions of lives. Hence, proper mitigation measures and planning is necessary to minimise destruction.