Newsletter No 4 December 2009

Climate Adaptation in Delta Cities

By Jeroen Aerts


The Connecting Delta Cities study is a joint initiative of the IVM, the City of Rotterdam, The Dutch ‘Knowledge for Climate’ Programme and others. The study explores the different aspects of climate adaptation in major coastal cities and compares adaptation problems and progress in the cities of Rotterdam, New York, London and Jakarta. The results of the study are summarized in a book and a documentary (
The study shows that climate change and sea level rise may exacerbate flood risks from storm surges as well as peak river discharges in large coastal cities. As a consequence, the vulnerability of infrastructure, people, nature and other economic sectors is expected to increase in the decades to come.
At present, more than 50% of the entire world population lives in cities. According to the United Nations, more than two thirds of the world’s large cities are vulnerable to rising sea levels, exposing millions of people to the risk of extreme floods and storms. Within the next 30 years, the United Nations predicts that the number of people living in cities will increase to 60% of the world’s population, resulting in even more people living in highly exposed areas. Hence, socioeconomic trends amplify the potential consequences of future floods, as more people move towards urban coastal centres and investments continues in ports and other infrastructures, industrial production and services. 

Both scientists and policy makers have addressed the issue of adapting to climate change, and both call for embedding long-term scenarios in city planning and investments in all sectors. The Stern Review presented a global estimate of the costs of adaptation to climate change, suggesting that for most countries, protection costs are likely to be below 0.1% of the gross domestic product (GDP), at least for protection measures that anticipate a 0.5-meter sea level rise. However, for the most vulnerable countries or regions, costs could reach almost 1% of GDP. Based on these estimates of adaptation costs, it appears that investing in adaptation now would save money in the long term. Developing and implementing adaptation measures is a complex process, and it is important that policy makers and investors do not inappropriately postpone taking decisions with long-term consequences.
Since the choices made today will influence vulnerability to climate risks in the future, it is important to link adaptation measures to ongoing investments in infrastructure and spatial planning, and to draw up detailed estimates of the benefits of adaptation. In this way, adaptation becomes a challenge rather than a threat, and climate adaptation may initiate opportunities and innovations for investors and spatial planners. Adaptation challenges include new engineering solutions, effective emergency management systems to address ever increasing flood risks, but also measures that use natural and environmental systems such as buffereing storm surges with coastal wetlands.
This requires, however, embedding climate change and adaptation considerations and long-term policy making into the daily operations of urban planners and policy makers. It also requires new legislation and urban building codes to ensure that plans are effectively implemented to meet climate-proofing standards, many of which still need to be developed. The adaptation planning process also requires a systems approach with full participation of stakeholders. If stakeholders are aware of climate risks, and the understandings and perceptions of the climate scientists, social scientists, and engineers whose responsibility it is to plan, design and build resilient infrastructure, it will be much more feasible to develop a workable adaptation plan for a city. The issue of climate adaptation and the role of spatial planners, water managers and other key stakeholders is too complex to tackle with a single disciplinary or sectoral approach.
Each city faces different challenges; one of the lessons of the Connecting Delta Cities initiative is that while cities will follow adaptation paths that may differ, each city can learn from the others.

For more information you can contact: Prof. Dr. Jeroen Aerts