UPSC Mains GS 1 | Tsunamis and Flash Floods – Week 113

QUESTION 1

Discuss the escalating hazard of flash floods in India due to climate change.

QUESTION 2

Discuss the geological and seismic factors responsible for the generation of tsunamis by earthquakes, using the recent Kamchatka earthquake as an example.

General points on the structure of the answers for UPSC Mains

Introduction

— The introduction of the answer is essential and should be restricted to 3-5 lines. Remember, a one-liner is not a standard introduction.

— It may consist of basic information by giving some definitions from the trusted source and authentic facts.

Body

— It is the central part of the answer and one should understand the demand of the question to provide rich content.

— The answer must be preferably written as a mix of points and short paragraphs rather than using long paragraphs or just points.

— Using facts from authentic government sources makes your answer more comprehensive. Analysis is important based on the demand of the question, but do not over analyse.

QUESTION 1: Discuss the escalating hazard of flash floods in India due to climate change.

Note: This is not a model answer. It only provides you with thought process which you may incorporate into the answers.

Introduction:

— India is highly vulnerable to floods. Floods are a recurrent phenomenon, which cause huge loss of lives and damage to livelihood systems, property, infrastructure and public utilities.

— According to the World Meteorological Organisation (WMO), “a flash flood is a flood of short duration with a relatively high peak discharge in which the time interval between the observable causative event and the flood is less than four to six hours”.

Body:

You may incorporate some of the following points in your answer:

Factors driving flash floods

— According to the study, only 25% of the flash floods that occur in India are directly caused by extreme precipitation. The rest of them are a result of a combination of extreme rainfall and the condition of the soil before precipitation.

— In the most vulnerable areas, various variables contribute to flash flood disasters. For example, in the west coast and Central India, flash floods are caused by the high flashiness of sub-basins (parts of larger river basins). This means that their water levels rise quickly following a significant rainfall event. Prevailing soil conditions have a significant impact on how quickly water infiltrates a subbasin.

— Geomorphological characteristics in the Himalayas, such as steep slopes and high relief (a landscape with a substantial difference between high and low points), contribute to flash floods.

Role of climate change

— According to a new study published in the journal Nature Hazards by researchers at the Indian Institute of Technology (IIT)- Gandhinagar, ‘Drivers of flash floods in the Indian sub-continental river basins’, flash floods are primarily concentrated in the Himalayas, the west coast, and Central India.

— With rising global temperatures, extreme weather events such as flash floods are becoming more frequent and intense around the world. This is because every 1 degree Celsius increase in average temperature allows the atmosphere to hold around 7% more moisture, resulting in more intense precipitation and increasing the risk of flash floods.

— Between 1981 and 2020, the pre-monsoon season in India saw a doubling of the annual frequency of extreme precipitation occurrences. Extreme rainfall during the monsoon, post-monsoon, and winter seasons has increased by 56%, 40%, and 12.5%, respectively, according to the study.

Conclusion:

— The number of flash flood events increased between 2020 and 2022 from 132 to 184, according to the Union Ministry of Jal Shakti’s written reply in the Lok Sabha in 2023.

— Despite the increasing threat posed by flash floods, there has been insufficient research to identify areas that are most vulnerable to this extreme weather event. This has posed a challenge in implementing adaptation strategies such as early warning systems.

(Source: How flash floods are affecting India)

Points to Ponder

Read more about floods and government’s initiatives to counter the problem of floods

How do cloudbursts contribute to flash floods in hilly regions?

Related Previous Year Questions

Discuss the consequence of Climate change on the food security in tropical countries. (2023)

The interlinking of rivers can provide viable solutions to the multi-dimensional inter-related problems of droughts, floods, and interrupted navigation. Critically examine. (2020)

QUESTION 2: Discuss the geological and seismic factors responsible for the generation of tsunamis by earthquakes, using the recent Kamchatka earthquake as an example.

Note: This is not a model answer. It only provides you with thought process which you may incorporate into the answers.

Introduction:

— Recently, a powerful magnitude 8.8 earthquake off Russia’s Far Eastern Kamchatka Peninsula triggered tsunami waves of up to 16 feet, which had started to American shores along Hawaii’s islands and off the coast of northern California. Tsunami alerts of varied levels have also been issued for countries such as Ecuador, Indonesia, Peru, Colombia, and Japan.

— An earthquake is an intense shaking of the ground caused by movement under the Earth’s surface. It happens when two blocks of the Earth suddenly slip past one another. This releases stored-up ‘elastic strain’ energy in the form of seismic waves, which spread through the Earth and cause the shaking of the ground.

— The Earth’s outermost surface, crust, is fragmented into tectonic plates. The edges of the plates are called plate boundaries, which are made up of faults — zones of fractures between two blocks of rock. The tectonic plates constantly move at a slow pace, sliding past one another and bumping into each other. As the edges of the plates are quite rough, they get stuck with one another while the rest of the plate keeps moving.

— Earthquake occurs when the plate has moved far enough and the edges unstick on one of the faults. The United States Geological Survey (USGS) says that “the location below the Earth’s surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the Earth is called the epicentre.”

Body:

You may incorporate some of the following points in your answer:

How does an earthquake lead to a tsunami?

— The earthquake must be a maritime occurrence that shifts the sea floor. It should also be a shallow earthquake, which carries more energy to the surface than deeper earthquakes. Deeper earthquakes spread farther as seismic waves flow radially upwards to the surface, but they lose energy as they travel longer distances. The Kamchatka quake had a magnitude of 8.8, and was one of the strongest earthquake since 1900.

— An earthquake resulting in a tsunami is typically caused by “reverse” faulting. In a reverse fault, the block of rock above the fault plane travels upward relative to the block below the fault plane. The fault motion is induced by compression forces.

— “If the earthquake is large enough and close enough to the ocean floor, the energy released can cause the ocean floor to suddenly raise (uplift) or plunge (subside). According to a National Oceanic and Atmospheric Administration (NOAA) research, a tsunami is primarily caused by a sudden vertical displacement of the ocean floor.

— Tsunamis are mainly caused by earthquakes with magnitudes greater than 7.0. However, the most damaging types of tsunamis are often triggered by earthquakes with magnitudes greater than 8.0. These tsunamis can travel long distances and cause widespread destruction.

Conclusion:

— In the case of the Kamchatka quake, the earthquake took place 136 km east of the coastal city of Petropavlovsk-Kamchatsky in Russia, and a shallow depth of just 19.3 km. That is one of the reasons why the earthquake was able to generate tsunami waves. The Kamchatka quake was also a result of reverse faulting. It has occurred as near the Kamchatka Peninsula is the Kuril-Kamchatka Trench, a tectonic plate boundary where the Pacific Plate is being thrust beneath the Okhotsk Plate at the rate of approximately 86 mm per year. This is a relatively high speed by tectonic standards, and causes large earthquakes to happen more frequently in the region.

(Source: How an earthquake can generate tsunami)

Points to Ponder

Read more about Tsunami and 2004 Indian Ocean tsunami

Read in detail about the Earthquakes

Related Previous Year Questions

What is the phenomenon of ‘Cloudbursts’? Explain. (2024)

Why are the world’s fold mountain systems located along the margins of continents? Bring out the association between the global distribution of fold mountains and the earthquakes and volcanoes. (2014)

Previous Mains Answer Practice

UPSC Essentials: Mains answer practice — GS 3 (Week 112)

UPSC Essentials: Mains answer practice — GS 3 (Week 113)

UPSC Essentials: Mains answer practice — GS 2 (Week 112)

UPSC Essentials: Mains answer practice — GS 2 (Week 113)

UPSC Essentials: Mains answer practice — GS 1 (Week 112)

UPSC Essentials: Mains answer practice — GS 1 (Week 111)

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