Date : 17/07/2023

Relevance –

• GS Paper 1 – Important Geophysical Phenomena
• GS Paper - 3 – Disaster Management, Environmental Pollution & Degradation

Keywords – Landslides, intense rainfall, ENSO, IOD, Climate Change

Context –

Several parts of India are currently witnessing a string of intense rainfall events, resulting in significant devastation, including landslides, flash floods, and loss of lives.

What are Causes of Heavy Rainfall in North India?

• The distribution and intensity of rainfall in India are influenced by multiple factors, including the monsoon, the western disturbance, the El Nino-Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and climate change.
• The heavy rainfall in North India can be attributed to the interaction between the monsoon trough (a low-pressure zone along the monsoon wind belt) and the western disturbance (a low-pressure system originating from the Mediterranean region). This interaction results in intense rainfall in states like Himachal Pradesh, Uttarakhand, Punjab, and Haryana.
• Initially, North India experienced a 10% deficiency in rainfall until the end of June. However, there has been a surge in monsoon activity, leading to a 2% excess rainfall over the country. Northwest India has witnessed a 59% excess rainfall, while peninsular India and east/northeast India have faced rainfall deficiencies of 23% and 17%, respectively.
• The recent heavy rainfall and flash floods in Himachal Pradesh share similarities with the synoptic conditions observed during the devastating 2013 Uttarakhand floods. These conditions involve an active monsoon with strong low-level easterly winds bringing abundant moisture, coupled with upper-level divergence caused by an eastward-moving trough. Climate change also contributes to increased heavy rainfall in hilly areas, such as the Himalayan foothills and the Western Ghats, due to additional moisture and orographic lifting.
• In hilly areas, the presence of hills obstructs the flow of moisture, causing it to accumulate and result in heavy downpours. Flash floods caused by cloudbursts and extreme rainfall events are challenging to predict. Effective monitoring and forecasting of such events require the use of radar systems and close observation of areas prone to flash floods. Additionally, land use changes and development activities can worsen the severity of flash floods.

What are the Factors Affecting the Rainfall in India?

Impact of Monsoon on Rainfall:

• The monsoon in India is characterized by a seasonal reversal of winds, bringing humid conditions and heavy rainfall. It typically occurs from June to September, with peak rainfall observed in July and August. The Indian Monsoon is driven by differences in air pressure between the Bay of Bengal and the Arabian Sea. The Thar desert and the Himalayas, along with temperature and pressure changes over the Indian Ocean, Arabian Sea, Bay of Bengal, and the southern Pacific Ocean, influence the distribution of rainfall in India.

Influence of Western Disturbance on Rainfall:

• The western disturbance is a low-pressure system originating from the Mediterranean Sea or West Asia, moving eastward towards India. While it primarily affects northwestern India during winter, it can also interact with the monsoon trough during summer, resulting in heavy rainfall in northern India. The impact of the western disturbance on monsoon activity depends on factors such as its location, intensity, and timing. When situated over northwestern India or Pakistan, it enhances the monsoon by providing moisture and atmospheric instability. Conversely, when located over central or eastern India, it can suppress the monsoon by creating a high-pressure system that blocks the monsoon winds.

ENSO's Influence on Rainfall:

• ENSO refers to periodic fluctuations in sea surface temperature and atmospheric pressure over the equatorial Pacific Ocean. It can affect rainfall patterns in India by altering atmospheric circulation over the Indian Ocean, Arabian Sea, Bay of Bengal, and the southern Pacific Ocean. El Nino events tend to weaken or delay the monsoon by creating a high-pressure system over India, impeding the moisture-laden winds. La Nina events, on the other hand, strengthen or advance the monsoon by creating a low-pressure system that attracts the moisture-laden winds.

Impact of IOD on Rainfall:

• IOD influences rainfall in India by modulating moisture transport and convection over the Indian Ocean, Arabian Sea, and Bay of Bengal. Its strength, duration, and timing can lead to varying effects across different regions. Positive IOD can increase summer rainfall in northwestern India and autumn rainfall in central India. Negative IOD can reduce summer rainfall in northwestern India while increasing autumn rainfall in peninsular India.

Climate Change and Rainfall:

• Climate change has the potential to impact rainfall patterns in India by altering temperature, humidity, pressure, wind, and cloud patterns over different scales of time and space. It can affect the monsoon by changing its onset, duration, intensity, and spatial distribution. Some studies suggest that climate change may delay the monsoon onset by increasing land-sea temperature contrast, hindering the northward movement of monsoon winds. Conversely, it may advance the monsoon by raising sea surface temperatures in the Indian Ocean, enhancing moisture supply to the atmosphere. Climate change can also increase the frequency and intensity of El Nino events, leading to reduced monsoon rainfall and increased droughts. Conversely, increased frequency and intensity of La Nina events can result in higher monsoon rainfall and floods. Additionally, climate change can impact orographic rainfall by influencing snow cover, glacier melt, and soil moisture in the Himalayas and Western Ghats.

What are the Implications of Heavy Rainfall in India?

• Agriculture:

• Excessive rainfall and floods can have detrimental effects on agriculture. They can damage crops, compromise soil fertility, disrupt irrigation infrastructure, and harm livestock. Moreover, these events can disrupt crucial agricultural activities such as crop sowing, harvesting, storage, and distribution. The resulting consequences can include food insecurity, malnutrition, poverty, and distress migration among farmers.

• Water Resources:

• While heavy rainfall and floods can replenish groundwater, surface water, and soil moisture levels, thereby positively impacting water resources, they also pose challenges. Waterlogging, erosion, sedimentation, landslides, dam breaches, and contamination of water sources are potential negative consequences. These can lead to water scarcity, conflicts over water usage, outbreaks of waterborne diseases, and the displacement of communities.

• Energy:

• Heavy rainfall and floods can have contrasting effects on the energy sector. On the positive side, they can increase hydropower generation by augmenting river flows and raising reservoir levels. Conversely, these events can disrupt thermal power generation by impacting coal supply and cooling systems. Additionally, damage to power plants, transmission lines, substations, and distribution networks can result in power outages, blackouts, financial losses, and safety hazards.

• Transportation:

• While heavy rainfall and floods can enhance water navigation by increasing water levels in rivers and lakes, they can also severely disrupt various modes of transportation. Landslides, floods, traffic jams, delays, cancellations, accidents, and fatalities can occur, affecting road, rail, air, and water transport networks.

• Health:

• In some positive aspects, heavy rainfall and floods can contribute to reducing air pollution by washing away dust particles and aerosols. They can also alleviate heat stress by lowering temperatures and humidity. However, these events can also lead to an increase in vector-borne diseases, posing health risks to affected populations.

Government initiatives to tackle flooding in India include:

1. National Flood Risk Mitigation Project (NFRMP): This project aims to mobilize resources and capabilities for relief, rehabilitation, reconstruction, and recovery from disasters. It also focuses on creating awareness among vulnerable communities.
2. National Disaster Management Plan (NDMP): The NDMP provides a comprehensive framework and direction for all phases of disaster management, including prevention, mitigation, preparedness, response, recovery, and reconstruction.
3. National Disaster Management Authority (NDMA): As the apex body for disaster management in India, the NDMA formulates policies, plans, and guidelines for disaster management. It coordinates the implementation of these measures across the country.
4. India Meteorological Department (IMD): The IMD provides crucial rainfall and cyclone forecasts, which are utilized by various agencies for flood preparedness. It issues warnings and advisories for heavy rainfall, flash floods, landslides, and cloudbursts.
5. Central Water Commission (CWC): The CWC monitors water levels in major rivers and reservoirs. It issues flood forecasts and inflow forecasts to aid in flood preparedness. The commission also conducts flood damage assessments and flood plain zoning. It provides technical guidance and assistance to state governments for flood management.
6. National Remote Sensing Centre (NRSC): The NRSC utilizes satellite-based information for flood monitoring, mapping, damage assessment, and relief planning. It develops flood inundation models and flood risk maps to support flood management efforts.

Way Forward

To tackle flooding, the government focuses on strengthening the institutional and legal framework, enhancing scientific and technical capabilities, and improving disaster preparedness. Here are some measures undertaken:

1. Strengthening Institutional and Legal Framework:

• Establishing dedicated agencies or departments for flood and landslide management.
• Enhancing coordination and collaboration among various stakeholders.
• Enforcing regulations and standards for land use, construction, and mining.
• Ensuring accountability and transparency in disaster management activities.

2. Enhancing Scientific and Technical Capabilities:

• Conducting hazard, vulnerability, and risk assessments.
• Mapping and zoning flood and landslide prone areas.
• Developing early warning systems and forecasting models.
• Implementing structural and non-structural mitigation measures.
• Promoting research, innovation, and capacity building.

3. Improving Disaster Preparedness:

Short-Term Measures:

• Establishing emergency control rooms and communication networks.
• Conducting drills and mock exercises to simulate response scenarios.
• Deploying rapid response teams and pre-positioning relief materials.
• Ensuring timely evacuation and rescue operations.

Long-Term Measures:

• Developing comprehensive disaster management plans at various levels.
• Allocating sufficient funds and resources for preparedness and response.
• Mobilizing community participation and increasing awareness through campaigns and education.

These initiatives aim to build resilience, improve response capabilities, and reduce the impact of flooding by addressing both immediate needs and long-term planning. It requires a multi-sectoral approach involving government agencies, local communities, scientific institutions, and other stakeholders.

Source – The Hindu