Bart Schultz
The climate in India is strongly influenced by the Himalayas and the Thar Desert; both drive the summer and winter monsoons. The Himalayas prevent cold Central Asian winds from blowing into the country. The predominant climate types are tropical wet, tropical dry, subtropical humid, and mountainous.
Major rivers originating in the Himalayas are the Ganges and the Brahmaputra, both of which flow into the Bay of Bengal via Bangladesh. Important tributaries of the Ganges are the Yamuna and the Kosi. The extremely shallow gradient of the Kosi, caused by prolonged silt deposition, leads to severe flooding and changes in the course of the river.
Major rivers on the mainland, whose greater gradient prevents flooding, include the Godavari, the Mahanadi, the Kaveri, and the Krishna, which also flow into the Bay of Bengal; and the Narmada and the Tapti, which flow into the Arabian Sea.
India's coastline is 7,520 kilometres long, of which 5,420 kilometres belong to the mainland and the others to the islands. The mainland coastline consists of 43% sandy beaches, 11% rocky coasts, including cliffs, and 46% mudflats or marshy shores. Characteristic coastlines include the marshy Rann of Kutch in West India and the Sundarbans in East India. The latter is shared with Bangladesh.
In the Ganges Delta of India, local farmers have reclaimed islands by constructing dams or ring dikes. In many cases, the elevation of these islands is not higher than 1.5 to two metres below high water level. Consequently, conditions for gravity drainage are poor, there are significant difficulties in closing dike breaches, and considerable damage can result from flooding. Reclamation of such land is therefore considered premature or untimely. According to Indian regulations, no land may be reclaimed until the elevation is higher than 0.3 to 0.5 metres below high water level.
As I described earlier in Polders in de regio Kuttanad, India on Flevolands Geheugen, the Kuttanad Polder in Kerala is in some places at three metres below MSL (mean sea level). In the area there are 1,231 polders with a total area of 55,000 hectares. The total area is 110,800 hectares, of which 28% is situated at approximately 1 metre above MSL, 60% at 0.6 to 2.2 m-MSL, and 12% consists of interconnected watercourses. This would imply that approximately 66,000 hectares are polders. In these areas, there were regular problems due to flooding during the wet monsoon and the intrusion of salt water during the dry monsoon.
To address these problems, the government of the State of Kerala launched a comprehensive plan for the development of Kuttanad in 1950. The plan included the Thottapally spillway (1955) to divert a portion of the floodwater from the upstream area of Kuttanad directly to the sea. Additionally, the plan provided for the construction of the Thanneermukkom Bund (1975–1981), a salt water barrier across the narrow section of Lake Vembanad, and a sluice at the southern boundary of the lowlands to prevent salt water from entering from the South. Since then, new land reclamation projects have taken place, the most recent of which are situated in water at 2.5 m-MSL.
In the Koshia Lagoon is a polder area of 50,000 hectares, and in the western Sunderbans an area of approximately 360,000 hectares. The total area of the salt lakes near Calcutta is approximately 12,000 hectares. Of this area, approximately 7,000 hectares have been reclaimed. In the state of Maharashtra, approximately 80,000 hectares of coastal area have been reclaimed. There are existing and proposed polders in the delta areas of the rivers along the east coast of India where polders are also present. For example, there are polders in the deltas of the Cauvery, Godavari, Krishna, and Mahanadi rivers.
Finally, there has long been a plan to close off the Gulf of Khambat and reclaim tidal areas within the gulf. If this were to happen, it would be by far the longest enclosure dam in the world. However, construction has not yet started.
