The Threat of Coastal Flooding

Twitter User: @c_heller “Another photo out of Breezy Point. The damage is stupefying. (Frank Franklin II, AP)″

In light of the devastation left by Hurricane Sandy, as politicians quabble over the existence of climate change, we cannot escape the reality that our cities are vulnerable to natural disasters. Coastal cities face the threat of flooding as sea levels rise and storms, as we’ve seem over the past few years, have had more severe impacts on our cities. The duty of architects, planners, and leaders is to build resilient cities with infrastructure that can stand up to the forces of natural disasters.

Join us after the break for a list of some of the largest port cities vulnerable to coastal flooding…

In 2007, the Organization for Economic Co-operation and Development (OECD) Secretary General Angel Gurría warned that impending climate changes required political commitment and a range of economic policies to handle its impacts. His statements were backed by a study of 130 key port cities world wide, and assessed the risk of and damage caused by a 1-in-100 year flood event in a research paper that assessed climate change.

An analysis of the vulnerability of these cities involves an assessment of a wide range of factors. The geographic location of these cities warns us which port cities are most threatened by rising sea levels, storm surges and damaging winds. But the extensive consideration to this list is given to the level of immediate and future impacts of a natural disaster by the factors of population, density, and economic and cultural assets. The study exposes fifteen countries with the highest populations that are vulnerable to such disasters and evaluates the exposed assets of the top ten countries.

In both scenarios, China tops the list with a population of 30 million and assets totaling $11 trillion. When the study was produced, it was predicted that Asian mega-cities would develop quickly and top the lists. By 2070, the study reads, eight of the most exposed cities will be in Asia.  The list, in order of vulnerability is: Miami, Guangzhou, New York, Calcutta, Shanghai, Mumbai, Tianjim, Tokyo, Hong Kong, and Bangkok. In general, Asia and North America top the list with the highest exposed population coupled with the highest exposed assets.

NYC, NY © Architecture 2030 / Google Maps

More specifically, China and the US have the most exposed cities that fit this scenario: 15 in China, 17 in American according to the 2008 OECD Study “Ranking Port Cities with High Exposure and Vulnerability to Climate Extremes“. Meanwhile, Architecture 2030 assessed US cities in 2007 for their vulnerability, assessing impacts based on a 1-meter rise. The results are startling, as images of coastal cities become half-hidden underwater. More than half of Miami is submerged, while images of NYC are eerily similar to reports of flooding during Hurricane Sandy.

A more recent study, published in June 2012, addresses the flood vulnerability index for coastal cities and develops a methodology for assessing the kind of damage that can be anticipated and its prolonged affects. It also provides a system by which cities can be assessed for ranking their vulnerability. In finding these weaknesses, this certainly provides insight into how these same cities can be made to be more resilient. The components of the assessment is divided into three systems: the Natural River Subsystem in which the physical, chemical and biological processes take place; the Socio-economic subsystem in which societal activities take place; and administrative and institutional subsystem that includes planning and management processes.

Miami, Florida © Architecture 2030 / Google Maps

Each subsystem of processes interacts with one another and outlines the vulnerability factor in question, in this case being coastal vulnerability. To better understand this assessment, the researchers developed components and factors for consideration. For example, within the natural system we must consider sea-level rise, storm surges, the number of cyclones, river discharge, foreshore slope, soil subsidence, and length of coastline. Each factor has an affect on and is affected by factors within the social, economic, administrative and institutional system. The social system includes factors of population close to the coastline and the culture which determines the level of interaction between the people and the natural elements as well as a sense of awareness and preparedness. An economic factor of consideration is how fast the population is growing and what the natural environment can accommodate as well as what measures are taken to protect the growing population. Institutional factors include the government’s assessment of the threats via zoning, flood hazard maps, awareness and protection.

New Orleans, Louisiana © Architecture 2030 / Google Maps

These factors, compounded together bring researchers into a closer understanding of how to evaluate the threat and vulnerability of a city. Each city can be studied according to each factor and averaged to determine its overall index. The AP has organized these findings to expose twelve of the largest cities that are vulnerable to coastal flooding via this interactive map. Calcutta tops the list with the highest population and property value at risk in 2070. It exposure along the Ganges River, susceptible to flooding, can inundate the mangrove forest’s natural barrier against cyclones and destroy the exposed slums along the river, targeting a population that is projected to grow to 14 million. New York City’s exposure was recently revealed as whole communities were swept away by flooding and wiped out by fire, lower Manhattan debilitated by power outages and infrastructure halted by flooding. It is 10th on the list, and one of two US cities, but its place on the list indicates that although it has components of the administrative and institutional subsystem, such as flood hazard maps and stringent building codes, it is still lacking in measures that could truly protect the city and population.

Assessing risk in the realm of trillions of dollars and populations in billions of people is a reminder of how vulnerable even the most developed cities are to natural disasters. There are many ways to handle the changes but, as the study reminds us, politicians and planners need to be forward thinking and willing to implement long-term strategies. It will require administrative forces to cooperate and work together to develop workable solutions, but that is only after we confront our vulnerability and that means acknowledging that the climate is changing, that weather patterns are not as predictable as they once were, and that we are seeing more extreme damage throughout the world.

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Cite: Irina Vinnitskaya. "The Threat of Coastal Flooding" 12 Nov 2012. ArchDaily. Accessed . <> ISSN 0719-8884

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