Sinking cities
[3] Sinking cities must overcome substantial barriers to properly prepare for today's dynamic environmental climate.
Soil fertility, availability of fresh water from rivers, accessibility due to flat topographical relief, and sea and waterways allowing for trade routes, have long made coastal plains valuable agricultural and economic resources.
[4] The growing physical risks to many coastal cities stem from a combination of factors relating to rapid urbanization, climate change, and land subsidence.
[2] In many cases, the fundamental aspects that lead to sinking cities become tightly interwoven, and over time, are increasingly difficult to resolve.
Once cities reach maturity, it can take decades for local governments to develop, fund, and execute major infrastructure projects to alleviate the issues brought on by rapid urbanization.
[2] Rapid increases in population growth challenge the carrying capacity of these urban environments often leading to mismanagement of natural resources.
Storm surges and high tides could combine with sea level rise and land subsidence to further increase flooding in many regions.
Direct impacts are often in the form of structural damage to major infrastructure systems, including water management networks, buildings, and highways.
[14] This downward settlement significantly increases flood vulnerability which can ultimately lead to major economic damages and loss of lives.
[18] Many cities do not possess the resources necessary to conduct complex, and often expensive, geological, geotechnical, and hydrogeological studies required to accurately measure and model future land subsidence.
[19] Although the early cultures drew water from the same lakes and aquifers, they were merely 300,000 people as compared to the city's current population of 21 million.
While natural catastrophes cause average economic losses between US$60–100 billion annually, a single large-scale disaster can easily surpass this, as proven by Hurricanes Sandy and Maria.
[3] Numerous sinking cities throughout the world are becoming ever more exposed to natural disasters, many of which, do not have the financial means to prepare for the impending storms.
In July and August, floods at high tide often near the subway level in Mumbai, clearly indicative of the impending climate dangers.
[20] Ho Chi Minh City currently accounts for 40% of Vietnam's GDP and has become especially vulnerable due to rising sea levels, land subsidence, and continued urbanization.
[2] Bangkok is also highly exposed to river flooding, as a major storm could have potentially massive impacts to the national economy.
New York City alone accounts for approximately 8% of the United States GDP and has experienced costly storms within the past decade.
Megaprojects, like The BIG U (NYC), have been proposed to help protect against future super storms and long-term sea level rise.
One report by OECD examined the vulnerability of 130 major port cities to climate change and found that by 2070 approximately half of the total population threatened by coastal flooding would reside in just ten megacities, all but one located in Asia.
[3] The urban poor will bear a disproportionate burden of climate change risk as they are likely to settle in areas most prone to flooding.
[24] In the coming decades, as impending storms begin to damage large sinking cities, environmental refugees are likely to become a global phenomena.
[2] This starts by conducting local and regional assessments that analyze city-level flood risks and culminates in creating a long term resiliency plan for cities.
International goals hope to reduce its impact throughout the twenty-first century, however, cities must design with climate adaptability in mind.
The cost of adaptation to climate change required by developing countries, mostly in Asia, is estimated by the World Bank at US$75–100 billion per annum.
[2] Construction of large seawalls, dikes, and diversion channels, are underway in many cities, but these solutions often only limit damage and must be combined with warning systems and evacuation plans.
Warning systems and evacuation plans are likely the only response in coping with large-scale disasters to avoid significant loss of life.
