By 2050, the sea level around the world is expected to rise by between 200 and 600 millimeters. One of the cities most at risk of flooding is New York.
Flooded roads, a dark city, reports of deaths… These were the consequences of Hurricane Sandy, which also hit New York in 2012. Something like this can happen again, and studies say that New York is more at risk of flooding every year. The city is sinking; on average by a millimeter to two per year. New York is considered the third most flood-prone city, and as many as 90 percent of the 67,400 buildings in flood-prone areas are not built to withstand floods. In connection with the third place mentioned above, it should be noted that this is a study by Hanon and colleagues, there are many studies that do not rank New York so high and place New Orleans higher among American cities in terms of flood risk.
764 million buildingsNew York’s skyscrapers are generally built on bedrock, but the bedrock is still sinking. The megalomaniac facilities themselves are said to have contributed to this. All New York buildings together are said to weigh around 764 million tons (one million and 85,000 buildings were taken into account in the calculation) and this weight is said to contribute significantly to the sinking. Although it is necessary to take into account that sinking is partly also a natural process.
Areas with clay floors and artificially packed material are most at risk, but the weight of the buildings is also not negligible. All of New York’s buildings together are said to weigh about 0.76 trillion kilograms, and this weight is said to be a non-negligible contributor to the sinking. It is also necessary to mention that the soil in some parts of New York is clayey or sandy, which in itself means a difficult base for buildings, even if they are not extremely tall. It is also disadvantageous that softer ground is more present in areas close to the sea.
Millimeters are decisiveThe team around geologist Tom Parsons in one the latest studies for buildings that are built on artificially filled ground, he notes that the potential for them to sink is between 7.5 and as much as 60 centimeters; and the average value is said to be 29 centimeters. For other soil types, it is estimated that buildings could sink between 6 and 12 centimeters. Interestingly, the subsidence is also thought to be a result of post-ice age conditions, when the retreat of the ice also affected the uplift/subsidence of the land and the height of the oceans. In the area of greater New York, it is possible to find a variety of material that was carried by glacial moraines when the ice melted due to melting.
For us, Parsons summed up the assessment of average conditions as follows. “On average, New York City is sinking a millimeter or two, up to 4.5 millimeters in some places. At the same time, sea level is rising by a millimeter or two, which means a relative rise of between two and 6.5 millimeters, depending on location. This increases the risk of flood damage over time .”
Lower Manhattan at riskLower Manhattan is most at risk of flooding, most of which is no more than a foot or two above sea level. The mentioned subsidence of a millimeter or two seems small, but even the most current study on subsidence says that even this much subsidence can contribute to the endangerment of buildings. It is also necessary to take into account that the rise of the level of sea ice on land means a risk for the foundations, which are more exposed to sea water and thus to corrosion. And as for sea level rise, it is currently estimated that it will rise between 200 and 600 millimeters globally by 2050. Interestingly, for New York, sea levels could rise three to four times the projected average rise along the North American Atlantic coast.
Some skyscrapers leanMore than 8.4 million people live in New York. The situation could even endanger lives at some point. There are known examples of buildings that are already leaning slightly due to the softer foundation, which does not mean that they will collapse. Just think of the Tower of Pisa or the Bell Tower of Venice. An example of this is the 58-story skyscraper known as One Seaport or 161 Maiden Lane, which is also one of those built in the popular super-slim skyscraper style, which slopes three inches to the top. For skyscrapers based on rocky foundations, the study does not predict any threat, except in the event that the rock is cracked. The rock is said to be mainly caused by the underground water system, which leads to the cracking of the sloping base. Parsonson’s study also points out that a good groundwater drainage system exists only on Long Island.
The reasons for the sinking are not fully explained. While they also emphasize the weight of skyscrapers in relation to lower Manhattan, the same cannot be said for areas in Brooklyn, Queens and northern Staten Island, which also show above-average subsidence in the context of greater New York. As Parsons says, “with man-made levees and historic wetlands that sink more than average.”
Architects are looking for solutionsUntil now, architects and urban planners from other parts of the world have also dealt with the problem of New York being endangered. A few years ago, for example, Danish architect Bjarke Ingels presented a high-profile project at the Venice Architecture Biennale. Lower Manhattan would be surrounded by a green belt, recreational areas with trees that tolerate salt water. They developed it all in accordance with the well-known ancient Greek idea that a society becomes ‘great’ when old men plant trees and know that they will never sit in the shade of their canopies.
It’s not just sinking. Climatologists warn that we can expect more tornadoes in the future. An indication of this was Tornado Ida in 2021, which overwhelmed the drainage system and parts of New York were once again under water. Tornadoes and storms, accompanied by strong winds in general, are also said to be caused by greenhouse gases. These are supposed to weaken the power of the natural wind barrier, which previously held back strong winds.
Source: Rtvslo
