Cyclone Vulnerability of India’s Eastern Coast

Cyclone vulnerability is the likelihood of suffering damage from cyclonic winds, storm surges, heavy rain and flooding. India’s Bay of Bengal-facing eastern coast is more vulnerable because cyclones form more frequently in that basin, their usual tracks favour east-coast landfalls, and the coast contains extensive low-lying deltas.

Higher cyclone frequency in the Bay of Bengal

The Bay of Bengal climatologically provides favourable warm, moist ocean-atmosphere conditions for cyclone formation. It also receives disturbances originating over the western Pacific and South China Sea that can regenerate after crossing Southeast Asia.

• Cyclone activity is concentrated particularly in the pre-monsoon and post-monsoon seasons, when vertical wind shear is relatively favourable.
• The Arabian Sea has historically produced fewer cyclones because monsoon winds, upwelling and dry-air intrusion often inhibit their development, although severe cyclones can still occur there.

Tracks and coastal configuration

North Indian Ocean cyclones commonly move initially westward or northwestward. This directs many Bay cyclones toward India, whereas similar movement over the Arabian Sea can carry storms away from the western coast.

• The funnel-shaped northern Bay of Bengal concentrates water toward the coasts of Odisha, West Bengal and Bangladesh.
• Broad, shallow offshore waters and gently sloping coasts can amplify the storm surge and allow seawater to penetrate farther inland.
• The Arabian Sea coast is generally narrower and steeper, except in areas such as Gujarat, which reduces surge penetration in many locations.

Greater exposure of low-lying coastal plains

The eastern coast contains wide deltaic plains formed by the Ganga-Brahmaputra, Mahanadi, Godavari, Krishna and Cauvery river systems. Their low relief, dense settlement and dependence on farming, fishing and coastal infrastructure increase potential losses.

• Cyclonic rain combines with river discharge and poor drainage to produce compound flooding across deltas and estuaries.
• The narrow western coastal plain and the nearby Western Ghats generally restrict the inland spread of coastal inundation, though they do not eliminate cyclone risk.