Asia's coastal megacities will flood more often, on a larger scale, and affect millions more people, if current climate change trends continue, a new report warns.
The report Climate Risks and Adaptation in Asian Coastal Megacities examines the impact of climate change on Bangkok, Ho Chi Minh City, and Manila, under a range of different scenarios through to 2050.
The report is the product of a two-year collaborative study by the Asian Development Bank (ADB), the Japan International Cooperation Agency (JICA) and the World Bank. It was released here today at the Asia Pacific Climate Change Adaptation Forum.
The report finds that costs from major flooding events on infrastructure and the economy could run into the billions of dollars, with urban poor populations likely to be the hardest hit. It concludes that all three cities need to take targeted, city-specific and cutting edge approaches to meet these challenges.
Bangkok, Ho Chi Minh City, and Manila all have populations close to or over 10 million. Two are capital cities and all three are centers of national and regional economic growth contributing substantially to the GDP of the respective countries.
As coastal megacities, all face increased climaterelated risks such as rising sea levels and an increased frequency of extreme weather events. While commendable measures to counteract flooding have already been taken by these cities, much more needs to be done, the report argues.
For cities to address future climate related risks, sound urban environmental management is crucial. Land subsidence due to groundwater pumping, dumping of solid waste into city canals and waterways, clogged drainage systems, and deforestation in the upper watershed all contribute to urban flooding. Better management of these urban environmental issues will help manage future climate-related impacts.
Given the damage costs associated with climate change, the report also recommends that governments of coastal megacities undertake proactive measures to address climate risks as an integral part of urban planning. This includes developing strategic urban adaptation frameworks for managing climate risks, strengthening institutional capacity for adaptation and implementing measures such as land use planning and zoning to help reduce urban vulnerability.
In Bangkok, flooding is caused by land subsidence and increased rainfall in the large watershed that drains through the city. Therefore, measures to control groundwater pumping, improve flood forecasting and information, raise dikes and invest in pump station capacity, are needed.
The threat from sea level rise and storm surges are found to be less dramatic, but still warrant investment in coastal zone protection and land use planning that takes a long-term perspective on these factors.
The report states that around 26% of the population is currently affected by extreme storm events, but those numbers could climb to more than 60% by 2050.
The government has expressed interest in a climate change adaptation plan for the city, which can provide an overall framework for adaptation measures within relevant sectors. Infrastructure-based approaches can also be usefully combined with ecosystems-based approaches such as management of mangroves and rehabilitation of urban wetlands.
In Metro Manila, the report states that in the worst case scenario a major flood could cause damage totaling almost a quarter of the metropolitan area's. The main threats to Manila are extreme rainfall, sea level rise, as well as more powerful typhoons. The report suggests that continuous improvements and redesigning of flood control infrastructure are necessary.
The report's findings on the three cities are a bellwether for coastal megacities around the world, from Asia to Africa. Its key messages include the following:
- Better management of urban environment and infrastructure will help manage potential climate-related impacts in coastal cities;
- Climate-related risks should be considered as an integral part of city and regional planning; and
- Targeted city-specific solutions, combining infrastructure investment, zoning, and ecosystem-based strategies are required.