New York, May 20 (IANS): New York City is sinking about 1-2 mm per year, from the weight of its skyscrapers, finds a study showing that the increasing sea level rise could put its over 8 million population at risk of coastal flooding.

The study, published in the journal Earth's Future, showed that the city faces accelerating inundation risk from sea level rise, subsidence, and increasing storm intensity from natural and anthropogenic causes.

Satellite observations made by researchers at the United States Geological Survey demonstrated an average 1-2 mm/year subsidence rate across New York City. However, certain parts of lower Manhattan, Brooklyn, Queens, and northern Staten Island were found to be sinking at a much faster rate of 2.75mm each year.

"New York is emblematic of growing coastal cities all over the world that are observed to be subsiding meaning there is a shared global challenge of mitigation against a growing inundation hazard," the researchers said, warning that new buildings in the city could be at increased threat of floods.

As coastal cities grow globally, the combination of construction densification and sea level rise imply increasing inundation hazard.

"Every additional high-rise building constructed at coastal, river, or lakefront settings could contribute to future flood risk," the researchers said, stressing the need to increase mitigation strategies.

Further, the researchers found that areas with clay-rich soil are likely to see an increase in subsidence "because of the material softness and ability to flow under pressure".

The study showed that major cities around the world are expected to grow disproportionately relative to rural areas, with a projected 70 per cent of the world's population living in cities by 2050.

Major cities on every continent except Antarctica are observed to be subsiding, and the issue may be worsened as populations grow.

"Increasing urbanisation will likely exacerbate subsidence by groundwater extraction and/or construction density, which combined with accelerating sea level rise implies a growing flood hazard in coastal cities," the geologists said, calling for mitigation strategies against inundation in growing coastal cities.