Coastal chaos

Sea surges will inundate coasts, causing enormous damages

Last Updated: Sunday 28 June 2015

Coastal chaos

Too high to handle: Coastal In (Credit: REUTERS)Global sea level has risen between 10-25 centimetres (cm) during the 20th century due to thermal expansion of the oceans, and melting of Antarctic and Arctic glaciers. The rate of sea-level rise during the 20th century was about 10 times higher than the average rate during the last 3,000 years. Global ocean heat content has also increased since the late 1950s. Sea level rise has significant socioeconomic implications for India (see box : Complex consequences).

Sea level rise will affect many regions of India, but the Andaman and Nicobar Islands and the coral atolls of the Lakshadweep archipelago are most vulnerable. According to a report on the impacts of climate change on India by the Asian Development Bank (adb), the entire population of Lakshadweep is at peril.

According to the adb study, a one-metre sea level rise will displace approximately 7.1 million people in India , as about 576,400 hectares (ha) of land area is lost, along with 4,200 kilometre (km) of roads. Land loss will account for 83 per cent of all damages.

In a case study of the Orissa and West Bengal region , ipcc estimates that in the absence of protection, a one metre sea level rise will inundate an area of 170,000 ha -- predominantly prime agricultural land -- and displace 0.7 million people . An additional 4,000 km of dykes and sea walls will be required to protect the area.

Many big Indian cities are situated on coasts, flood plains and river deltas, supporting a large number of people. Large coastal cities can expect increased flood damage, including that from storm surges and higher wave activity. There will be loss of structures and property. Disappearing shorelines also mean some loss of social amenities.

The economic impacts of climate change on a city like Mumbai could be as high as us $48 billion (Rs 2,28,700 crore), while those for Balesore could be us $75 million (Rs 360 crore).

Both religious and resort-based coastal tourism will suffer in case of sea level rise. According to the adb study, Goa, one of the smallest coastal states, will lose 4.32 per cent of its total area . Its famous beaches and tourist infrastructure like beach-based hotels are very vulnerable.

Coastal erosion will increase substantially, endangering natural protective features such as sand dunes, mangroves, and barrier islands, and exacerbating flood risk. Many coastal communities depend on fisheries and these will be damaged.

Deltas and low-lying coastal areas will be inundated by sea level rise. Increased rainfall during the monsoons will increase the frequency of floods. Areas already prone to floods will suffer more.

Most coastal regions, which are agriculturally fertile with paddy fields, are vulnerable to inundation and salinisation.

Rising sea levels will put millions of people at greater risk of storm-related flooding. In an area like Bangladesh, where storm surges can reach as far as 200 km inland during intense cyclones, the increase in flood risk could greatly magnify the already high toll associated with such storms. A one metre rise in sea level could inundate 17 per cent of Bangladesh's total land area and displace 11 million people. According to ipcc, a smaller rise of 45 cm would result in a land loss of 1,566,800 ha leading to 5.5 million people being displaced. This will cause a large influx of refugees into India, which will further increase if there is political instability in Bangladesh.

In the case of West Bengal, most of the area likely to be lost includes the Sunderban mangrove swamps and reserved forests. This will mean a large loss of wildlife, useful biodiversity and lifestyle.

All these factors imply a displacement of large numbers of people, which will lead to rapid urbanisation, straining resources and putting more pressure on civic amenities.

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