Physical Geography of Tamil Nadu Exercise Solutions | KalviGavani

Tamil Nadu extends from 8°4'N to 13°35'N latitude and 76°18'E to 80°20'E longitude. It is bounded by Andhra Pradesh and Karnataka on the north, Karnataka and Kerala on the west, the Bay of Bengal on the east, and the Indian Ocean on the south. The state covers an area of 1,30,058 sq km and has a coastline of 1,076 km — the second longest among Indian states.

| Feature | Western Ghats | Eastern Ghats | |---|---|---| | Continuity | Continuous, unbroken | Discontinuous, broken by rivers | | Height | Higher (900–2,695 m) | Lower (average ~600 m) | | Rainfall | Windward side gets heavy rain | Rain-shadow, less rainfall | | Key Hills | Nilgiri, Anaimalai, Palani, Cardamom | Javadi, Shevaroy, Kalrayan, Pachamalai | | Vegetation | Dense evergreen and shola forests | Deciduous and thorn forests |

Most rivers of Tamil Nadu originate in the Western Ghats or the higher plateaus on the western side and flow eastward because the land slopes from west to east — the Western Ghats are on the western edge and the Bay of Bengal is to the east. Gravity and the general slope of the Peninsular plateau direct these rivers towards the Bay of Bengal. The Western Ghats act as a watershed dividing east-flowing and west-flowing rivers of the peninsula.

The major tributaries of the Cauvery are: 1. Left bank: Hemavathi, Harangi, Lakshmanatheertha, Shimsha, Arkavathi 2. Right bank: Kabini (Kapila), Suvarnavathi, Bhavani, Noyyal, Amaravathi Of these, the Bhavani, Noyyal, and Amaravathi flow through Tamil Nadu. The Cauvery and its tributaries form the fertile Cauvery delta — the rice bowl of Tamil Nadu.

The Coromandel Coast is the eastern coastal plain of Tamil Nadu along the Bay of Bengal. Its significance: 1. It has fertile river delta plains (especially the Cauvery delta) that support intensive paddy cultivation. 2. Major ports like Chennai, Cuddalore, and Tuticorin are located here, enabling trade. 3. Fishing is a major livelihood along this coast. 4. However, the coast is prone to cyclonic storms during the northeast monsoon (October–December). 5. Lagoons and backwaters like Pulicat Lake are found along this coast.

1. Tamil Nadu has a tropical climate — generally hot throughout the year. 2. The temperature ranges from about 18°C in hill stations to over 40°C in interior plains during summer. 3. Unlike most of India, the northeast monsoon (October–December) brings the highest rainfall (~48%), not the southwest monsoon (~32%). 4. Annual rainfall varies from about 60 cm in the rain-shadow areas to over 300 cm in the Western Ghats. 5. The coastal districts experience cyclonic storms during the northeast monsoon season.

1. Coimbatore Plateau: Located between the Nilgiri and Palani Hills in western TN; well-watered by rivers; suitable for agriculture and industry. 2. Madurai Plateau: Found in the southern interior; undulating terrain; relies on monsoon rainfall and Vaigai river irrigation. 3. Tirupathur Plateau: Part of the eastern district plateaus; less fertile; used for dry farming. The plateaus are part of the larger Deccan Plateau and generally have red soil, moderate elevation, and support dry farming.

| Dam | River | District/Purpose | |---|---|---| | Mettur Dam | Cauvery | Salem — irrigation, hydro-power | | Bhavanisagar Dam | Bhavani (Cauvery tributary) | Erode — irrigation | | Vaigai Dam | Vaigai | Theni — irrigation for Madurai region | | Papanasam Dam | Tamiraparani | Tirunelveli — irrigation, hydro-power | | Amaravathi Dam | Amaravathi (Cauvery tributary) | Tiruppur — irrigation | | Sathanur Dam | Thenpennai (Pennaiyar) | Tiruvannamalai — irrigation |

Tamil Nadu has four major physical divisions, each with distinct characteristics: 1. Western Ghats (Hilly Region): The Western Ghats run continuously along the entire western border of Tamil Nadu, from the Nilgiris in the north to the Cardamom Hills in the south. Key sub-ranges include: - Nilgiri Hills: Home to Dodabetta (2,637 m), the highest peak in the Nilgiris. The Nilgiris are a junction where the Western and Eastern Ghats meet. - Anaimalai Hills: Contain Anai Mudi (2,695 m), the highest peak in peninsular India. - Palani Hills: Lie east of the Western Ghats; Kodaikanal hill station is located here. - Cardamom Hills: Southern part of the Western Ghats; known for spice plantations. - Varushanad Hills: Source of the Vaigai river. The Western Ghats receive heavy orographic rainfall on the windward side (2,500–5,000 mm) and create a rain-shadow effect on the leeward side. 2. Eastern Ghats: The Eastern Ghats are discontinuous and broken by river valleys (Palar, Pennaiyar, Cauvery). Key sub-ranges include the Javadi Hills, Shevaroy Hills (Yercaud), Kalrayan Hills, and Pachamalai. They are lower than the Western Ghats (average ~600 m) and receive less rainfall. 3. Plateaus: The Coimbatore Plateau (between Nilgiri and Palani Hills) and the Madurai Plateau (southern interior) are the major plateau regions. They are part of the Deccan Plateau and have undulating terrain with red soil, suitable for dry farming and, where irrigation is available, wet cultivation. 4. Plains: - River valley plains: The Cauvery delta (Thanjavur, Nagapattinam, Tiruvarur) is the most fertile and densely populated. Other valleys include the Vaigai and Tamiraparani flood plains. - Coastal plains (Coromandel Coast): The 1,076 km coastline supports ports, fishing, and agriculture. However, the coast is vulnerable to cyclones during the northeast monsoon.

The Cauvery (Kaveri) River System: The Cauvery is the most important river of Tamil Nadu. It originates at Talakaveri in the Brahmagiri Hills of Coorg district, Karnataka, at an elevation of about 1,341 m. Course: 1. Flows southeast through Karnataka (Mysore, Mandya). 2. Enters Tamil Nadu at Hogenakkal (famous for its waterfalls). 3. Flows through Erode, Tiruchirappalli, Thanjavur. 4. Splits into multiple distributaries in the delta (Cauvery, Kollidam, Arasalar, Vennar). 5. Empties into the Bay of Bengal at Poompuhar. Major Tributaries in Tamil Nadu: Bhavani, Noyyal, and Amaravathi (right bank). Dams and Reservoirs: Mettur Dam (Stanley Reservoir), Bhavanisagar, Krishnarajasagara (Karnataka), and Grand Anicut (Kallanai) — one of the oldest dams in the world, built by Karikala Chola. Importance: - The Cauvery delta (Thanjavur, Nagapattinam, Tiruvarur) is called the "Rice Bowl of Tamil Nadu" for its intensive paddy cultivation. - Supports irrigation for over 10 lakh hectares of farmland. - Hydroelectric power generation at Mettur, Bhavanisagar, and other dams. - Cultural and religious significance — the river is worshipped as a goddess. - Major cities like Tiruchirappalli and Erode depend on the Cauvery for drinking water and industry. Other Major Rivers: | River | Origin | Significance | |---|---|---| | Vaigai | Varushanad Hills | Irrigates Madurai and Ramanathapuram; Vaigai Dam | | Tamiraparani | Pothigai Hills | Only major river entirely within TN; irrigates Tirunelveli and Thoothukudi | | Palar | Nandi Hills, Karnataka | Flows through Vellore and Kanchipuram districts | | Pennaiyar | Chenna Keshava Hills, Karnataka | Flows through Dharmapuri and Cuddalore districts |

Climate Overview: Tamil Nadu has a tropical climate with three distinct seasons: 1. Summer (March–May): Hot and dry; temperatures reach 40°C+ in interior plains; coastal areas are slightly cooler due to sea breeze. 2. Southwest Monsoon (June–September): Brings rain to the Western Ghats windward side but most of Tamil Nadu lies in the rain-shadow region; only about 32% of annual rainfall. 3. Northeast Monsoon (October–December): The primary rainy season for TN; contributes about 48% of annual rainfall. Moisture-laden winds from the Bay of Bengal bring heavy rain and sometimes cyclonic storms to the coast. 4. Winter (January–February): Mild and dry; temperatures drop slightly, especially in hill stations. Why the Northeast Monsoon Is More Important: 1. Rain-shadow effect of Western Ghats: During the southwest monsoon, the Western Ghats block moisture-laden winds. By the time these winds cross the Ghats, they have lost most of their moisture. Tamil Nadu lies on the leeward side and receives little rain. 2. Bay of Bengal moisture: During the northeast monsoon, winds pick up moisture from the warm waters of the Bay of Bengal. When these winds hit the eastern coast and the Eastern Ghats, they cause heavy rainfall. 3. Cyclonic activity: Low-pressure systems and cyclonic depressions in the Bay of Bengal during October–December bring intense rainfall to the coastal districts. These cyclones can be destructive but are a major source of water. 4. Rainfall distribution: Coastal districts like Chennai, Cuddalore, and Nagapattinam receive 60–70% of their annual rainfall during the northeast monsoon. The Western Ghats districts receive rain from both monsoons. Rainfall Data (approximate): | Region | Annual Rainfall | Main Source | |---|---|---| | Western Ghats (Nilgiri, Coimbatore) | 2,500–5,000 mm | Both monsoons | | Coromandel Coast (Chennai, Cuddalore) | 1,200–1,500 mm | Northeast monsoon | | Interior plains (Madurai, Tirunelveli) | 800–1,200 mm | Northeast monsoon | | Rain-shadow areas (Erode, Salem interiors) | 600–800 mm | Northeast monsoon + thunderstorms |

Tamil Nadu has five major soil types, each supporting different agricultural patterns: 1. Black Soil (Regur Soil): - Distribution: Coimbatore, Madurai, Tirunelveli, Virudhunagar, Dindigul - Characteristics: High clay content, moisture-retentive, cracks in summer, becomes sticky when wet - Agricultural significance: Ideal for cotton cultivation (hence called "black cotton soil"); also suitable for millets, tobacco, and pulses. Requires less irrigation because of moisture retention. 2. Red Soil: - Distribution: Largest area in TN — Sivagangai, Ramanathapuram, Tiruvannamalai, Vellore, Dindigul, Pudukkottai - Characteristics: Porous, less fertile than alluvial, reddish colour due to iron oxide; loses moisture quickly - Agricultural significance: Suitable for pulses, groundnut, millets, and ragi. Requires irrigation or depends on monsoon rainfall. 3. Alluvial Soil: - Distribution: Cauvery delta (Thanjavur, Nagapattinam, Tiruvarur), Vaigai delta, Tamiraparani delta - Characteristics: Very fertile; composed of silt and sand deposited by rivers; good water-holding capacity - Agricultural significance: Best soil for paddy (rice) cultivation; also supports sugarcane, banana, and plantation crops. The Cauvery delta is the most productive agricultural region in TN. 4. Laterite Soil: - Distribution: Kanyakumari, Western Ghats slopes (Nilgiri foothills) - Characteristics: Formed by intense leaching of silica and accumulation of iron and aluminium oxides; porous, poor in organic matter - Agricultural significance: Suitable for cashew, tea, coffee, rubber, and tapioca. Requires heavy fertilisation for food crops. 5. Sandy Soil: - Distribution: Coastal areas — Chennai, Cuddalore, Nagapattinam, Ramanathapuram coast - Characteristics: Low fertility, high permeability, low water-retention, saline in patches - Agricultural significance: Suitable for casuarina, coconut, palmyra palm, and groundnut with irrigation. Not suitable for water-intensive crops. Soil Conservation in Tamil Nadu: - Afforestation on hill slopes to prevent erosion - Contour bunding and terracing on sloping land - Crop rotation and mixed cropping to maintain soil fertility - Preventing over-irrigation in delta areas to avoid salinity

Factors Affecting Natural Vegetation: 1. Rainfall: Varies from 600 mm in rain-shadow areas to over 4,000 mm on Western Ghats windward slopes — the single most important factor. 2. Temperature: Ranges from near-freezing in Nilgiri peaks to over 40°C in interior plains. 3. Soil: Black soil supports thorn forests; alluvial soil supports moist deciduous trees; laterite supports evergreen species. 4. Altitude: Vegetation changes from tropical at sea level to montane (shola-grassland) above 1,500 m. 5. Human activity: Deforestation, agriculture, and urbanisation have significantly reduced forest cover. Types of Natural Vegetation: | Type | Rainfall Required | Key Species | Regions | |---|---|---|---| | Tropical Evergreen | >200 cm | Rosewood, mahogany, ebony, rubber | Western Ghats (Anaimalai, Cardamom Hills, upper Nilgiris) | | Tropical Deciduous | 100–200 cm | Teak, sandalwood, neem, sal | Central TN plateaus, foothills of Eastern and Western Ghats | | Thorn and Shrub | <75 cm | Acacia, babul, euphorbia, cactus | Ramanathapuram, Sivagangai, interior rain-shadow areas | | Mangrove | Tidal/estuarine | Rhizophora, Avicennia, Bruguiera | Pichavaram (Cuddalore), Muthupet (Thiruvarur) | | Montane Shola-Grassland | >150 cm at altitude >1,500 m | Shola trees (Mesua, Michelia), grasses | Nilgiri Hills, Palni Hills above 1,500 m | Forest Cover in Tamil Nadu: - Tamil Nadu has about 20% of its geographical area under forest cover. - The Nilgiri Biosphere Reserve is a UNESCO World Heritage Site spanning TN, Karnataka, and Kerala. - Important wildlife sanctuaries and national parks: Mudumalai (Nilgiri), Anaimalai (Coimbatore), Kalakad-Mundanthurai (Tirunelveli), Guindy (Chennai), Vedanthangal (bird sanctuary, Kanchipuram). Map Reference for Vegetation: - Mark the Western Ghats for evergreen and montane forests - Mark the central and eastern plateau for deciduous and thorn forests - Mark Pichavaram and Muthupet for mangroves - Mark the Nilgiri and Palni high-altitude areas for shola-grassland