If Your City Is Sinking, Why Not Make It Float?

MIAMI - May 16, 2023 - PRLog -- By: Katherine Dafforn, Macquarie University in Sydney

Many of the world's largest coastal cities are sinking at alarming rates due to factors such as groundwater extraction and the weight of built infrastructure.

A potential solution is moving their residents to floating cities, if they can be built without creating a damaging ecological footprint in the ocean.

The issue of land subsidence or 'sinking' is not a new one. Vertical subsidence of up to 9m has been observed in coastal areas during the 20th century.

The issue has been gaining increasing global attention because the areas most prone to sinking are megacities that house almost 20 percent of the global urban population, and these areas are also the most heavily impacted by sea level rise.

Given that almost half of the 48 largest coastal cities are sinking at a rate faster than 10mm per year there is an urgent need for viable solutions.

Current approaches have tended to focus on trying to hold back the sea and building up coastal defences through hard engineering or nature-based solutions, but when subsidence is combined with sea level rise even the lowest projections will prove challenging for engineering works.

So-called sponge cities that can absorb and reuse water have been touted as one potential solution, but they address intermittent flooding rather than creeping sea level rise and eventual permanent inundation.

With more than 40.5 million people already displaced as a result of the climate crisis, the need to relocate people, businesses and even cities to safer regions is an increasing reality.

Where an inland movement is impossible then floating cities may be a way forward in addressing overdevelopment, sea level rise and land subsidence.

The idea that cities could be built to float is not a new concept and apart from existing floating villages in places like Thailand, the Philippines and Vietnam there has been an ongoing architectural debate since the 1950s that has recently gained significant traction with the United Nations calling for research into floating cities.

Technically, there are two types of structure that could support a floating city — pontoon structures that float on the water's surface and semi-submersible structures like oil rigs that have submerged pontoons connected to an operating deck by structural columns.

While there are still no floating cities in the ocean, the closest proposal is Oceanix which is based on a pontoon structure and so requires shallower waters and some protection from wave energy.

A prototype — Oceanix Busan — is due to begin construction in 2023 in South Korea and will start with three connected, floating islands including a lodging platform, research platform and living platform.

Climate info:
https://youtube.com/channel/UCW8SVBv-3IlwjMTHDuAdPeQ