New Delhi, Jun 15 (KNN) Many major coastal cities are slowly sinking into the oceans owing to rapid industrialization, with many cities experiencing emergency flood conditions. Other cities will follow according to a BBC report that lists Mumbai and Kolkata among those at high risk.

The report has attributed the occurrence, to rise in sea level because of climate change and as a consequence of global warming.

“Over 3 billion people live in coastal city areas that are at risk of rising sea levels and other consequences of global warming,” it said. It goes on to say that Shanghai is the most vulnerable major city in the world to serious flooding.

The report while exploring the reasons for such a devasting impact dwells at length on the reasons for the threat of cities being submerged in water. 

Given that most of us now live in cities, they have spread and replaced wild lands, while using up energy from fossil fuels. These cities are bound to grow even bigger as humans carry out the greatest ever urban migration, the report said.

However, “Many won’t survive the changes humanity is wreaking on the planet, let alone natural upheavals.”

Rapid increase in population is among the major causes for changes in our rivers which are trapped for water storage while also being depleted by droughts and other extractions. The situation has been further complicated by the erosion of oceans, depletion of ground water, melting of glaciers and rise in sea levels.

Other cities in the high risk category are Guangzhou, Bangkok, Shanghai, Miami, Ho Chi Minh City, New York City, Osaka-Kibe, Alexandria and New Orleans.

Currently, more than three billion people live in coastal areas facing risk of global warming impact which include rising sea levels. This is expected to increase to six billion people by 2025.

The impact has already been felt at different locations – In the Netherlands some 50 million cubic metres of sediment has to be dredged from inland water channels or the sea every year to help maintain current shorelines.

Meanwhile, during Hurricane Sandy in 2012, as many as 100,000 extra people were at risk of flooding for every foot of water in New York.   More than half of the population of America’s coastal cities live below the high-tide mark.

Globally, the urban construction boom is causing flooding, erosion and loss in water and soil quality elsewhere, as sand is mined and rivers are dredged to provide building materials for the new cities.

Shanghai is particularly vulnerable to flooding as groundwater extractions and sea-level rise hasten the sinking of its massive high rise buildings into the East China Sea. Parts of the city have sunk three metres. In response, the authorities have begun pumping 60,000 tonnes of water a year back into wells to reduce the subsidence, built hundreds of kilometres of levees and are planning an emergency floodgate on the river’s estuary to protect the nation’s most prosperous city and its 20 million inhabitants.

Mexico City is suffering a similar fate, with parts of the city subsiding 9 metres (30 feet) since 1910 through over-pumping of groundwater.
In Ho Chi Minh City, high tides can cause floods for as many as 10 days per month. Sandbags are often ineffective because the water comes up into the house through the sewage systems.

As a solution, some cities are investing in new sea walls, dykes and polders, or high-tide gates – like London’s Thames Barrier – to hold back high waters. In poorer places, people simply endure the problem until they are forced to abandon their homes.

Our industrial pollution is impacting the man-made world as surely as it is affecting the natural world. Millions of years from now, there may be few signs of the mighty cities that have transformed our planet. (KNN)