into Kerala. The Idamala gorge separates the Sholayar forests in the Nelliyampathies towards the north from the southern Anamudi Reserved Forest and High Range Plateau. The area belonging to Tamil Nadu in the Periyar basin is situated here. This area forms the north-eastern corner of the Periyar basin. It is drained by the tributary Nirar, which runs in a South Westerly Direction and falls into Idamalayar. Within this section there are a series of deep west-sloping valleys where the valley floors are often at elevations less than . Separating these valleys are a jumble of steep hills and flat topped plateaux with scarp faces rearing up to elevations of around . The Idamala and Pooyamkutty rivers drain most of this section while its southern edge drains into the main Periyar. This tract is almost entirely forested and the forests extend northwest between Periyar and Chalakudy rivers along the plains almost up to Kalady. Periyar Midlands and Lowlands To the west of the Lower Periyar Valleys are the midlands, which are characterized by undulating topography with small hills separated by valleys. The general gradient is towards the west here. The lowlands occur as a narrow belt almost parallel to the present shoreline. The landforms of this section are broad valleys, submerged lands with swamps and marshes and subdued sand dunes. Many parts of the area are directly connected to the backwaters with a network of canals. The river bifurcates near Aluva into two major distributaries; one continues to flow through Desam as Mangalappuzha and finally drains into the Lakshadweep Sea. The Chalakudy river also joins to this branch of the Periyar south-east of Kodungalloor which expands to its maximum width at Munambam. The Marthandavarma branch flows southwards, again dividing into two near Kunjunnikkara Island, and finally drains into the Vembanad backwaters at Varapuzha. The most industrialized zone of Periyar lies in this part of the basin between Angamaly and Cochin, with over 50 large and medium scale industries. The Edayar branch of Periyar caters to the needs of these industries. Dams Hydro-electric projects The Idukki Dam is the largest hydro-electric project in Kerala and lies on the Periyar. It is the biggest dam of its kind (a concrete, double curvature parabolic, thin arc dam) in Asia and the second-biggest in the world. Its generators have a power output of 780 MW (), and generate electricity through the underground facility at Moolamattam,