Ranking port cities with high exposure and vulnerability to climate extremes - Scoping study
| Division | Energy and Climate Change | ||||||||||||||
| Research Centre | Coastal Engineering and Management | ||||||||||||||
| Project Website | |||||||||||||||
| Project Staff |
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Introduction
 Ports-location_map2.jpg) Location of port cities assessed during this scoping study |
Exposure
The analysis demonstrates that a large number of people are already exposed to coastal flooding in large port cities. Across all cities, about 40 million people (0.6% of the global population or roughly 1 in 10 of the total port city population in the cities considered here) are exposed to a 1 in 100 year coastal flood event.
For present-day conditions (2005), the top ten cities in terms of exposed population are estimated to be Mumbai, Guangzhou, Shanghai, Miami, Ho Chi Minh City, Kolkata, Greater New York, Osaka-Kobe, Alexandria and New Orleans; almost equally split between developed and developing countries. The distribution becomes more heavily weighted towards developed countries when assets are considered, i.e. the top 10 cities are Miami, Greater New York, New Orleans, Osaka-Kobe, Tokyo, Amsterdam, Rotterdam, Nagoya, Tampa-St Petersburg and Virginia Beach which account for 60% of total asset exposure. The total value of assets exposed in 2005 is across all cities considered here is estimated to be US$3,000 billion; corresponding to around 5% of global GDP in 2005 (both measured in international USD).By the 2070s, total population exposed could grow more than threefold to around 150 million people due to the combined effects of climate change (sea-level rise and increased storminess), subsidence, population growth and urbanisation. The asset exposure could grow even more dramatically, reaching US $35,000 billion by the 2070s; more than ten times current levels and rising to roughly 9% of projected global GDP in this period.
On a global-scale, for both types of exposure, population growth, socio-economic growth and urbanization are the most important drivers of the overall increase in exposure. Climate change and subsidence significantly exacerbate this effect although the relative importance of these factors varies by location. Exposure rises most rapidly in developing countries, as development moves increasingly into areas of high and rising flood risk.
 Exposed_pop2.gif) Population exposed to sea-level rise, storm surge and subsidence in 2070, by country |
Vulnerability
It must be emphasised that exposure does not necessarily translate into impact as exposed
population and assets are often protected. However protection can fail and the linkage between exposure and the residual risk of impact therefore depends upon the standard and maintenance of flood (and wind) protection measures. In general, cities in richer countries have higher protection levels than those in the developing world. Hence, even assuming that protection levels will be very high everywhere in the future, the large exposure in terms of population and assets is likely to translate into regular city-scale disasters across the global scale. The policy implications of this report are clear: the benefits of climate change policies - both global mitigation and local adaptation at the city-scale - are potentially great.
The study also provides interesting insights into future vulnerability on a national scale. The analysis reveals that 90% of the total estimated 2070s asset exposure in large port cities is concentrated in only eight nations (China, US, India, Japan, Netherlands, Thailand, Vietnam and Bangladesh). For population, 90% of the exposure in the 2070s is contained in eleven countries (again, China, USA, India, Japan, Thailand, Vietnam and Bangladesh as well as Myanmar, Egypt, Nigeria and Indonesia). The concentration of future exposure to sea level rise and storm surge in rapidly growing cities in developing countries in Asia, Africa and to a lesser extent Latin America, urgently underscores the need to integrate the consideration of climate change into both national coastal flood risk management and urban development strategies. Given the heavy concentration of people and assets in port city locations, and the importance in global trade, failure to develop effective adaptation strategies would inevitably have not just local but also national or even wider economic consequences.
It must also be noted that those cities with greatest population exposure to extreme sea levels also tend to be those with greatest exposure to wind damage from tropical and extra-tropical cyclones. For example, the ten cities with highest exposure to wind damage are also among the Top 20 cities exposed to presentday extreme sea levels. These include Tokyo, New York, Shanghai, Kolkata, Dhaka, Osaka, Mumbai, Guangzhou, Shenzen and Miami. All except Shenzen have also been identified as having high (Top 20) exposure to coastal flood risk in the 2070s. To an extent, this is to be expected, given the role of high winds in driving extreme sea levels. A main conclusion is that these cities may experience combined perils of growing storm surges and more intense winds, and therefore must incorporate both perils into their adaptation and risk management strategies.
Policy implications
The policy implications of this report are clear: the benefits of climate change policies; both global mitigation and local adaptation at the city-scale are potentially great. As reported in the IPCC Fourth Assessment Report, global mitigation can slow and limit the exacerbating effects of climate change on coastal flood risk, at a minimum buying precious time for cities to put adaptation measures in place. As cities are also responsible for the majority of greenhouse gas emissions they are also key actors in the design and implementation of mitigation strategies. In parallel, effective adaptation is essential for managing risks against the background of developing cities and the changing climate. Coastal cities will face great challenges in managing the significant growth in exposure that will come about from both human and environmental influences, including climate change. The size and concentration of population and economic development in many of the world’s largest port cities, combined with climate change, highlights the strong two-way linkage between development and climate change and the need for more effective governance for climate change adaptation at the city-scale.
Effective adaptation strategies will require multilevel governance approaches to assist port cities to understand and to pro-actively manage current and future flood risk. The large amount of future port city asset exposure on its own (as much as US$35,000 billion in the 2070s) argues for proactive adaptation which will require a much more focused effort across scales of governance (global, local and public-private) to advance adaptation measures to manage these risks in port cities. Putting into place effective disaster management strategies, land use practices and protection investments will take time. Previous defence projects (e.g., the Thames Barrier) have shown that implementing coastal protection infrastructure typically has a lead-time of 30 years or more. The inertia of the socio-economic response suggests that action must begin today to protect port cities and to manage flood risk for impacts expected by the middle of this century.
The concentration of these risks in a few of the world’s cities and nations underscores the urgent need for leadership and attention in these locations. Such action could inform effective management responses, a knowledge base that could help to advance action in many other locations in the coming decades.
Collaborators:
Risk Management Solutions (RMS)
OECD
Centre International de Recherche sur l’Environnement et Développement et École Nationale de la Météorologie
Publications associated with this grant
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