The Coastal Plains of India are a crucial physiographic division formed by a combination of marine action, river deposition, and tectonic movements (subsidence and emergence). Stretching over a coastline of 7,516.6 km (including island territories), the mainland coastal plain extends for about 6,100 km. It is flanked by the Arabian Sea on the west and the Bay of Bengal on the east, covering a total area of approximately 2.5 lakh square kilometers.
| Parameter | Western Coastal Plains | Eastern Coastal Plains |
| Location | Sandwiched between the Western Ghats and the Arabian Sea. | Sandwiched between the Eastern Ghats and the Bay of Bengal. |
| Nature of Coast | Primarily a coastline of submergence (except the Malabar coast). | Primarily a coastline of emergence. |
| Width | Narrower (average width 50–65 km; narrowest in Karnataka). | Wider (average width 80–120 km; widest in the Mahanadi and Krishna-Godavari deltas). |
| Geomorphic Features | Characterized by estuaries, creeks, backwaters (Kayals), and lagoons. | Characterized by massive deltas, sandbars, and spit lakes. |
| River Systems | Short, swift rivers with high gradients (e.g., Narmada, Tapi, Mandovi) forming estuaries. | Long, sluggish rivers with large catchment areas (e.g., Mahanadi, Godavari, Krishna, Kaveri) forming deltas. |
| Port Suitability | Highly favorable for natural, deep-water ports due to submergence. | Less favorable for natural ports; requires regular dredging due to shallow waters and siltation. |
The Western Coastal Plain
The Western Coastal Plain is a narrow alluvial strip extending from the Gulf of Kachchh in the north to Kanniyakumari in the south. It is divided into four distinct regional sub-divisions based on geomorphological variations.
Kachchh and Kathiawar Peninsula
- Kachchh Region: An area of marine deposition and tectonic upliftment, characterized by the Great Rann of Kachchh (a salt-encrusted desert plain) and the Little Rann. It remains isolated during the monsoons due to shallow marine inundation.
- Kathiawar Plain: Situated south of Kachchh, it features the central Mandav Hills and the Gir Range (famous for the Asiatic Lion). The region is drained by radial river systems like the Bhadar and Shetrunji.
Gujarat Plain
- Geomorphic Extension: Formed by the alluvial deposits of the Sabarmati, Mahi, Narmada, and Tapi rivers east of Kachchh and Kathiawar.
- Features: Slopes gently toward the south and southwest. It includes the fertile cotton-growing tracts of southern Gujarat and extensive mudflats along the Gulf of Khambhat.
Konkan Coast
- Geomorphic Extension: Extends from the Daman in the north to Goa in the south, spanning a length of about 500 km.
- Features: Highly dissected, rocky, and narrow coast with cliffs and pocket beaches. It experiences high rainfall and contains rich laterite soils. Major urban centers like Mumbai and Goa are situated on this stretch.
Karnataka (Kanara) Coast
- Geomorphic Extension: Extends from Goa southwards to Mangaluru, covering a length of roughly 225 km.
- Features: A narrow plain where the Western Ghats closely approach the sea. It features waterfalls like the Jog Falls (Sharavati River) due to the steep gradient of short westward-flowing rivers.
Malabar Coast
- Geomorphic Extension: Extends from Mangaluru to Kanniyakumari, spanning the state of Kerala.
- Features: Relatively wider than the Konkan and Karnataka coasts. It is universally recognized for its extensive network of brackish lagoons, backwaters (locally called Kayals), and barrier islands.
The Eastern Coastal Plain
The Eastern Coastal Plain is an extensive stretch of land lying between the Eastern Ghats and the Bay of Bengal. It is characterized by prograding deltas and proscenium shelves.
Utkal Plain
- Geomorphic Extension: Covers the coastal areas of Odisha, encompassing the deltaic plains of the Mahanadi, Brahmani, and Baitarani rivers.
- Features: Dominated by the Chilika Lake, which is the largest brackish water lagoon in India and a designated Ramsar site. The plain features wide sandy beaches and coastal sand dunes.
Andhra Plain
- Geomorphic Extension: Extends from the southern limit of the Utkal Plain to the Pulicat Lake in the south.
- Features: Formed by the deltaic advances of the Godavari and Krishna rivers. The active progradation of these deltas has pushed the coastline outward, turning the once coastal Kolleru Lake into an inland freshwater lake.
Tamil Nadu (Coromandel) Plain
- Geomorphic Extension: Extends from Pulicat Lake to Kanniyakumari, covering a length of about 675 km.
- Features: Dominated by the fertile Kaveri Delta, often referred to as the “Granary of South India.” The coastline features the Pulicat Lake (a large barrier lagoon shared with Andhra Pradesh) and Sriharikota Island, which acts as a barrier separating the lake from the Bay of Bengal.
Key Geomorphic Features and Strategic Significance
Lagoons, Backwaters, and Lakes
- Chilika Lake (Odisha): Located south of the Mahanadi delta, it is a classic example of a spit-formed lagoon and is highly biodiverse, supporting the Irrawaddy dolphins.
- Pulicat Lake (Andhra Pradesh/Tamil Nadu): A major brackish water lagoon barred by the Sriharikota island, hosting the Satish Dhawan Space Centre.
- Vembanad Lake (Kerala): The longest lake in India and the core of the Malabar backwater system. It hosts the annual Nehru Trophy Boat Race (Vallam Kali).
Ports and Harbors
- Western Coast Ports: Kandla (tidal port), Mumbai (largest natural harbor), Jawaharlal Nehru Port Trust/Nhava Sheva (largest container port), Mormugao, New Mangalore, and Kochi.
- Eastern Coast Ports: Kolkata-Haldia (riverine port), Paradip, Visakhapatnam (deepest landlocked and protected port), Chennai (oldest artificial port), Kamarajar (Ennore), and Tuticorin.
Economic and Ecological Significance
- Agriculture: The Eastern deltas are highly intensive rice-cultivation zones. The Western plains support plantation crops like coconut, areca nut, rubber, and spices.
- Mineral Wealth: High concentration of monazite sands (source of thorium) along the Kerala coast. The offshore regions (Bombay High, Krishna-Godavari Basin) are major hubs for petroleum and natural gas exploration.
- Blue Economy: Supports massive marine fisheries industries and provides vital installations for renewable energy (coastal wind farms and tidal energy prospects).