Chennai Port - Location and Geography

Location and Geography

Chennai Port lies on a flat coastal plain known as the Eastern Coastal Plains on the east coast of the Indian peninsula known as the Coromandel Coast in the Bay of Bengal. The bed slope is fairly flat. The port is situated on the thermal equator and is also coastal, which prevents extreme variation in seasonal temperature. The climate is tropical, specifically tropical wet and dry, and for most of the year, the weather is hot and humid, with temperatures ranging from a maximum of 42°C in May to a minimum of 18°C in January. The mean minimum temperature is 18°C in January and 26.8°C in May. The mean highest temperature is 29.3°C in December and 39.6°C in May. The port gets most of its seasonal rainfall from the northeast monsoon winds, from mid-September to mid-December. Occasionally, cyclones in the Bay of Bengal hit the coast. The average annual rainfall in the region is about 1298.11 mm, with 443.5 mm during southwest monsoon (June–September), 753.1 mm during northeast monsoon (October–December), 37.3 mm during winter season (January–February) and 64.2 mm during hot weather (March–May). The monthly average varies from 7 mm in April to 308 mm in November. Humidity ranges from 63 to 83 percent during January–March, from 57 to 72 percent during April–June and from 70 to 81 percent during October–December.

The tides in the port area are semi-diurnal in nature, that is, occurrence of two high and two low waters every day. The spring tides are up to 1.2 m (3 ft 11 in). The mean tidal range varies from 0.914 m to 1.219 m at spring and from 0.805 m to 0.610 m at neap tides. The change in water levels combined due to astronomical tide, wind setup, wave setup, barometric pressure, seiches and global sea level rise are estimated as 1.57 m, 1.68 m and 1.8 m at 15 m, 10 m and 5 m depth contours, respectively. Waves ranging from 0.4 m to 2.0 m in the deep water around Chennai harbour have been experienced with the predominant being 0.4 m to 1.2 m with wave periods predominantly in the order of 4 to 10 seconds. During cyclone season, waves of height exceeding 2.5 m are common. The predominant wave directions during southwest and northeast monsoons are 145° from north and 65° from north, respectively.

The most prevailing winds in the region are the southwesterly between April and October and the northeasterly during the rest of the year. The predominant wind direction is mostly from W and SW direction during the rainy season and SW and NW during post-monsoon month. However, during January to March, winds from NE and E direction are predominant. During the northeast monsoon, that is, between October and January, the direction of wind is generally NE and NNE. During depressions in northeast monsoon, the wind velocity goes up to 50 km/h and up to 105 km/h during cyclones of duration 2 to 3 days. Gusts of 160 km/h have been occasionally experienced. During southwest monsoon between March and September, the wind blows predominantly from the south. During June, July and August, strong wind is experienced from southwest direction in mornings, from south during afternoons, and from southeast during nights. Wind direction is between 153° and 263° relative to the north, and the wind speed varies from 2 to 12 m/s.

Situated on a coast that constitutes chiefly of sandy shelving breaker-swept beaches, the region surrounding the port falls under Seismic Zone III indicating a moderate risk of earthquake. The port was developed into the sea by reclaiming land as there is no sheltered harbour. The depth of the draft is up to 17 m, and the soil in the entrance channel is predominantly sandy and silt. The port is bordered by the Cooum delta in the south and Royapuram fishing harbour in the north. Visibility in the harbour region is good throughout the year and low visibility is commonly associated with heavy rains during the northeast monsoon.

Historically, the port was responsible for the shoreline changes in the region, where the area south of the port has accreted significantly, resulting in the formation of the Marina Beach, whereas the coast in the northern region has undergone severe erosion. Ever since the harbour was constructed, the coast north of the harbour has been experiencing erosion at the rate of about 8 m annually. The shoreline has recessed by about 1,000 m with respect to the original shoreline in 1876. It is estimated that 500 m of beach has been lost between 1876 and 1975 and another 200 m between 1978 and 1995. About 350 ha land in the coast north of the port is lost into sea. On the other hand, the area south of the port is increasing 40 sq m every year due to the progradation.