Case Study - II - Class 8 PDF Download

Assam

• The Ganga-Brahmaputra-Meghna Basin, a 1,000-km floodplain, is flood-prone.
• The Brahmaputra river basin carries 60% of India’s water supply.
• About 40 million hectares of this area are at risk of flooding.
• The Brahmaputra, older than the Himalayas, is Assam’s lifeline.
• It flows through steep gorges in Arunachal Pradesh, widening to 16 km in Assam.
• The river runs 720 km through the Brahmaputra Valley.
• Monsoons hit Assam from early June to mid-October.
• Cherrapunji and Mawsynram, south of the valley, get the world’s heaviest rainfall.
• The southwest monsoon brings 65% of Assam’s yearly rain.
• Districts like Dibrugarh, Sivasagar, Jorhat, North Lakhimpur, Golaghat, and Majuli Island face severe floods.

Cause of Floods in Assam

• Brahmaputra, Barak, and tributaries overflow during monsoons, causing floods.
• Assam gets 2,800 mm of rain yearly, more than Odisha (1,400 mm), Gujarat (800 mm), and Bihar (1,200 mm).
• Heavy rain creates a bottleneck, overwhelming water bodies.
• An 8.6 magnitude earthquake on August 15, 1950, altered Tibet and northeast India’s topography.
• Post-quake, streams rose higher and tributary courses shifted, worsening floods.
• Deforestation causes soil erosion, swelling rivers.
• Human actions like urban growth and filling low areas increase flood risks.

Bihar

• Bihar faces floods, droughts, earthquakes, heat/cold waves, river erosion, and fires.
• Bordered by Nepal (north), West Bengal (east), Uttar Pradesh (west), and Jharkhand (south).
• Rivers include Ganga, Son, Punpun, Falgu, Karmanasa, Durgavati, Kosi, Gandak, and Ghaghara.
• Heavy rain falls from June to October.

Causes of Floods in Bihar

• Northern plains flood due to rivers from Nepal with steep slopes flattening in Bihar.
• Silt from these rivers piles up at the base, triggering floods.
• The Ganga, Bihar’s lifeline, flows west to east, joined by Ghaghara, Gandak, and Kosi.
• Kosi, dubbed ‘the sorrow of Bihar,’ is wide and shifts course, causing destruction.
• Deforestation in Nepal’s catchment area adds silt, leading to floods.
• Dams hold water, but excess rain forces gate openings, causing overflows.

Impact of Floods in Assam and Bihar

• Floodwaters collapse buildings, injuring or killing people.
• Physical and emotional health suffers, e.g., hypothermia from long exposure.
• Water contamination from chemical spills spreads cholera and dysentery.
• Stagnant water pools breed mosquitoes, causing malaria and dengue.
• Strong currents wash away animals, especially in the Brahmaputra.
• Grazing animals in Kaziranga National Park lack fodder during floods.
• Silt from Brahmaputra floods fragments beels (lake-like wetlands).
• Beels and water bodies, vital for ecology, are disrupted by floods and human actions.
• Floods damage roads, bridges, patrolling paths, and guard camps in parks.
• Communication between camps and headquarters becomes tough during floods.

Measures to Reduce Flood Damage

• Soil protection: Plant roots hold soil, preventing washaway.
• Avoid deforestation, overgrazing, and overcultivation to protect soil.
• Dams control river overflow.
• Flood control: Build dykes, dams, and reservoirs to hold water.
• Water management improves river flow.
• Advance warning: Flood forecasts and warnings help us to act fast in fighting against floods and in minimising the damage caused.