6.5   Plains

. Plains The plains of Tamil Nadu may be divided into two, namely . Inland plains . Coastal plains Inland plains are drained by the rivers Palar, Ponnaiyar, Cauvery and Thamirabarani. Cauvery plains is one of the most important fertile plains of the state. The plains of Cauvery  Physical Geography of Tamil Nadu Then Pennaiyar/Then Ponnaiyar It originates from the eastern slope of Nandi Durga hills in eastern Karnataka. It drains an area of , sq.km, of which nearly % lies in Tamil Nadu. It flows for a distance of km in the southeasterly direction in the districts of Krishnagiri, Dharmapuri, Vellore, Tiruvannamalai, Cuddalore and Villupuram. It branches into two, viz. Gadilam and the Ponnaiyar near Tirukoilur Anaicut. Gadilam joins the Bay of Bengal near Cuddalore and Ponnaiyar near the Union Territory of Puducherry. Chinnar, Markandanadhi, Vaniar and Pambar are its tributaries. Heavy rain at the river’s source cause sudden but short-lived floods. The river is extensively dammed for irrigation, especially in Tamil Nadu. There are reservoirs at Krishnagiri and Sathanur across this river. Vaigai Vaigai river rises from the eastern slopes of the Varusanadu hills of Western Ghats of Tamil Nadu. It drains an area of , sq.km, which lies entirely in the state of Tamil Nadu. It flows through the districts of Madurai, Sivaganga and Ramanathapuram. Its length is km. It discharges its water into the Ramnad Big Tank and some other small tanks. The surplus water from the tanks is finally discharged into Palk Strait near Ramanathapuram. Thamirabarani The name is interpreted as Thamiram (copper) and Varuni (streams of river). The water of this river gives a copper like appearance due to the presence of dissolved suspended red soil. It originates from a peak in Pothigai hills on the Western Ghats above Papanasam in the Ambasamudram taluk. It courses through the districts of Tirunelveli and Thoothukudi and finally flow into the Bay of Bangal near Punnaikayal in Thoothukudi district. Karaiyar, Servalar, Manimuthar, Gadananathi, Pachaiyar, as the Stanley Reservoir, is located across this river