Model Answer

India has witnessed an increasing trend of severe urban flooding, affecting major cities such as Bengaluru (2022), Hyderabad (2020), and Chennai (2015). Traditional flood management methods, particularly “Grey Infrastructure” like dams, seawalls, and drainage systems, have proven insufficient in addressing the growing challenge of urban flooding, especially with climate change and rapid urbanization.

Limitations of Grey Infrastructure

• Overwhelmed Systems: During heavy rainfall, existing grey infrastructure often fails due to the insufficient capacity of pipes, poor maintenance, and ineffective pumping stations.
• Climate Change Impact: Increased rainfall intensity and erratic weather patterns exacerbate the inadequacies of current drainage systems.
• Urbanization Pressure: As cities grow, the strain on existing infrastructure increases, making it harder to upgrade and maintain systems capable of handling higher run-off volumes.

The Shift to Nature-Based Solutions (NBS)

Given these limitations, there is an urgent need to explore alternative flood management strategies. Many global cities have adopted Nature-Based Solutions (NBS), which focus on restoring and mimicking natural processes to reduce flood risks.

Alternative Approaches to Urban Flood Management

1. Urban Green Spaces: Establishing urban forests, terraces, open green spaces, and corridors can help absorb excess water and reduce flood risks.
2. Eco-Friendly Practices: Techniques like urban farming, bioretention areas, and the restoration of wetlands, rivers, and floodplains can be incorporated into city planning to manage water flow naturally.
3. Notable Initiatives in India:
   • Guwahati: Focus on afforestation and preservation of wetlands.
   • Bhopal: Implementation of the Green and Blue Master Plan to address drainage and environmental issues.
   • Chennai: The ‘Water as Leverage’ initiative focuses on sustainable water management.
4. National Adoption: With India’s urban population expected to reach 814 million by 2050, integrating NBS into Master Plans and urban renewal schemes is crucial.

Conclusion

To effectively combat urban flooding, it is essential to shift from traditional grey infrastructure to nature-based solutions that align with environmental sustainability and the needs of rapidly growing cities.

Model Answer

The significant reduction in the Greenland Ice Sheet’s (GrIS) surface mass, the largest drop since 1948, is mainly driven by the following factors:

1. Increased Surface Meltwater: Rising air temperatures, especially during the summer, heat the glacier’s surface. This causes the formation of meltwater pools that leak through the ice and flow to rivers below the surface. These pools accelerate the glacier’s melting as they drain into the sea.
2. Warm Ocean Water: As meltwater flows into the sea, it mixes with the warmer, saltier ocean water at the bottom of the fjords. This creates a plume that drags warm water beneath the glacier, leading to further melting at its base.
3. Calving and Ice Discharge: The interaction between meltwater and warm ocean water results in calving, where large chunks of ice break off and become icebergs. This process accelerates the overall mass loss from the glacier.
4. Global Warming: The Arctic is warming at a rate significantly faster than the global average. Since 1991, temperatures in Greenland have increased by about seven degrees Fahrenheit, leading to increased melting of the ice sheetonsequences of GrIS Shrinkage
5. Sea-Level Rise: The melting of the Greenland Ice Sheet contributes to rising sea levels, which enhances coastal erosion and elevates storm surges. This results in more frequent and intense coastal storms like hurricanes and typhoons .
6. *Weather D: Melting ice alters ocean circulation and disrupts weather patterns. This includes changes to the polar vortex, leading to more erratic weather outside the Arctic .
7. Impact on Ecosysteans: Rising sea levels threaten coastal communities and ecosystems. Species such as polar bears and walrus lose their habitat, and industries reliant on stable weather and ocean conditions, like fisheries, will be impacted .

If current melting rates persistnland Ice Sheet could cause a sea-level rise of up to 20 feet by the end of the century .

Model Answer

Frontogenesis occurs when two distinct air masses with different properties converge. The necessary conditions for this process are:

• Temperature Contrast: The air masses must have significant temperature differences. A warm, moist, and light air mass meets a cold, dry, and dense air mass. The disparity in temperature creates a sharp boundary, which is essential for frontogenesis.
• Convergence of Air Masses: The meeting of two air masses with different characteristics leads to the formation of a front. As the air masses try to invade each other’s space, they trigger the development of a front.

Frontogenesis does not occur in the equatorial regions because air masses in this area are uniformly warm, which prevents the formation of fronts.

Global Distribution of Fronts

Fronts develop in specific regions around the world, where temperature gradients and air mass convergence are pronounced:

• East Asia and Eastern North America: Fronts form primarily in winter due to sharp temperature contrasts between snow-covered lands and warm offshore currents. The Pacific Arctic fronts are created along the Rockies-Great Lakes region.
• North Atlantic and North Pacific: The North Atlantic experiences frequent frontal activity, while this decreases in the North Pacific due to a lower temperature gradient in the sea surface.
• Mediterranean: The Mediterranean front forms when cold polar air from Europe meets warm, dry air from North Africa. This frontogenesis occurs mainly in winter, and the frontal zone disappears during summer due to anticyclonic conditions.
• Atlantic Arctic Front: This front forms when maritime polar air meets air masses from the Arctic boundary, resulting in distinct weather patterns.

Each type of front brings different weather phenomena, such as precipitation from cold fronts or drizzly rain from warm fronts.

Model Answer

The spatial distribution of both volcanoes and earthquakes across the globe exhibits a striking similarity, with both phenomena occurring along well-defined belts or zones. This pattern is largely explained by the Theory of Plate Tectonics, which associates these events with the movement and interactions of Earth’s tectonic plates.

Key Belts for Earthquakes and Volcanoes

1. Circum-Pacific Belt (Ring of Fire):
   • This is the most active zone for both earthquakes and volcanoes. It includes the Pacific Ocean’s eastern and western coastal areas, island arcs, and volcanic islands scattered across the Pacific. Most of the largest earthquakes and volcanic eruptions in history have occurred herelpide Belt (Alpine-Himalayan Belt).
   • Running from Java to Sumatra, through the Himalayas and Mediterranean, this belt also hosts significant earthquake activity. Similarly, volcanic zones are found in the Alpine mountain chains and along the Mediterranean Sea, showing a close correlation between earthquakes and volcanic activity in this region.
2. Ridge Belt:
   • Volcanoes along the mid-Atlantic Ridge, where tectonic plates diverge, also align with areas of frequent seismic activity. As plates pull apart, magma rises to form new oceanic crust, causing both volcanic eruptions and earthquakes.

The Role Tectonics

Both earthquakes and volcanoes are closely linked to the movement of tectonic plates. Earthquakes occur due to the release of energy from fault lines, while volcanoes form at convergent and divergent plate boundaries. The motion and interaction of plates—whether colliding, pulling apart, or sliding past each other—result in seismic and volcanic activity in these specific zones.

Model Answer

The drainage system of the Himalayas has been significantly shaped by the natural process of river piracy, also known as stream capture or stream diversion. This occurs when one river captures the flow of another by headward erosion or lateral erosion.

The Role of River Piracy in the Himalayas

River piracy has been a driving force in developing the Himalayan drainage system, especially in its youthful stages. During this time, rivers engage in headward erosion, lengthening their valleys and shifting water divides. More powerful rivers, with higher gradients and greater kinetic energy, can capture weaker rivers.

Notable Examples of River Capture

1. Yarlung Tsangpo and the Brahmaputra: The Yarlung Tsangpo River was captured sequentially by the paleo-Red, Irrawaddy, and Lohit Rivers before it was finally captured by the Brahmaputra. This process showcases how river piracy has redirected the flow of major rivers in the region.
2. Arun Kosi and Phung Cho: The Arun Kosi, a tributary of the Kosi River, captured Phung Cho, a tributary of the Tsangpo (upper Brahmaputra). This is another example of headward erosion leading to river capture.
3. Bhagirathi and Vishnuganga: The Bhagirathi and Vishnuganga rivers, head tributaries of the Ganga, captured tributaries of the Sutlej River, further altering the drainage network.
4. Saraswati River Deviation: It is believed that the deviation in the course of the Saraswati River was caused by river piracy, with the Yamuna River capturing its flow through headward erosion.

Current Examples and Future Possibilities

The Song River, a tributary of the Ganga, may eventually capture the Asan River, redirecting the upper Yamuna’s course into the Ganga. This illustrates how river piracy is still active in the region today.

Thus, river piracy has played a crucial role in forming the Himalayan drainage system, shaping the course of rivers over time.