This month sees the one year-anniversary of Hurricane Sandy, perhaps the largest Atlantic storm ever. Almost 300 people were killed along the hurricane’s pathway across some seven countries. In the United States, alone, the costs are estimated at some $70 billion, making this the second costliest storm in US history.
What was particularly striking, to many, was the ferocity of waves and the tidal surge in shallow waters by coastlines. In Manhattan, for instance, water levels easily exceeded previous highs.
One year on from Sandy, substantial money and effort has gone into rebuilding the areas most devastated by the storm. However, the much under-appreciated fact is that many other areas of the world, including in the United States, are just as vulnerable to intense flooding.
The unfortunate truth is that existing flood protection in most countries is simply not fit for purpose. Even in our native Netherlands, a world leader in flood management, around one third of the 3,800 kms of flood protection defences is sub-standard.
The combined impact of climate change, subsidence, urban growth and socio-economic change mean that average global flood losses could rise drastically if no adequate risk reduction measures are implemented. Areas in the United State, alone, that are at significant risk from flooding due to storms and hurricanes include: Miami, Tampa Bay, and the Galveston/ Houston area of Texas.
Other regions are at risk from river flooding include the Sacramento – San Joaquin Delta in California. Even New Orleans, despite some 14 billion dollars of post-Karina investments in hurricane protection, still has relatively high risk.
In developing countries, vulnerability is growing particularly rapidly too, especially due to economic growth and lack of investment in flood protection infrastructure. Many growing megacities, including Guangzhou, Ho Chi Minh City, and Bangkok, are located in deltas at significant risk from flooding.
It is crystal clear that a new global agenda to enhance flood protection infrastructure is badly needed. And that this must be started now.
Having faced water hazards for generations, the Dutch are eager to share their experience in planning and design of effective systems to reduce storm surge risk. Our experience is mainly in protecting the country against flooding. For densely populated areas, this strategy is much more cost efficient than moving people, planning measures or evacuation measures.
Based on Dutch best-practice, it is evident that much more investment is needed in flood management globally. With a population of almost 16 million, the government already spends about 0.2% of GDP on managing a complex and sophisticated network of storm surge barriers, pumping stations, dykes, levees, locks, harbours, and dams. Despite this investment, it is anticipated that costs could rise substantially due to aging infrastructure and future demands associated with sea level rises.
Another lesson is that appropriate flood management requires continuous attention, expertise and expenditure over the long term. The Dutch have recently decided to allocate a Delta fund which will guarantee continuous streams of investment in flood management, including maintenance, research and innovation for decades.
Other countries will need to also raise their own investment, some markedly so. A realistic target for flood adaptation is probably around 0.1-0.2% of the GDP at risk, so large but affordable.
There is not a one-sized-fits-all solution to water hazards. Instead, a combination of measures will be needed combining ‘hard’ options (e.g. engineering of barriers and levees), ‘soft’ measures (e.g. building with natural solutions), and also ‘hybrid’ approaches (e.g. vegetated foreshores for dikes).
One effective solution for protecting coastal metropolitan areas are storm surge barriers. However, the construction and maintenance costs are high -- often billions -- and there might be adverse effects for navigation and the environment. Various regions such as New Orleans and St Petersburg have implemented this solution, and other cities such as Shanghai and the Houston / Galveston region are studying this option.
In the current proposals for New York, there is a preference for more localised options, including flexible flood defences for low-lying areas at waterfronts and protection measures to flood-proof subway and road tunnel systems. Also softer solutions such as enhancing wetlands in Jamaica Bay and nourishments and dunes in front of coastal towns are proposed.
The solutions that New York eventually chooses will be relevant for other flood-prone regions. This is not just for areas at risk in the United States, like the Houston-Galveston region and Sacramento, but also delta regions in other parts of the world where people face the challenging question of how to achieve sustainable flood protection.
A final part of this new agenda must be better distribution of roles and responsibilities between governments and the private sector, especially given the innovation and large sums of money that will be needed. After the floods in Thailand and New York, the private sector has invested heavily in flood protection. Examples are the substantial floodwalls built around industrial estates in Thailand, and measures implemented by companies in New York.
This is positive, but care is needed that these local flood protection measures do not negatively affect other areas and parties at risk. Therefore, there will always remain a key role for government to develop a long-term plan for flood management.
This agenda is as serious as it is pressing. However, it is an unfortunate reality that societies often only seem willing to invest in adequate flood risk reduction after large disasters. Given the scale of risks in coming decades, this attitude must now change for reasons both of human security and financial cost.
Bas Jonkman is a professor of hydraulic engineering at Delft University of Technology. This blog was co-authored with Mathijs Van Ledden, who is director of flood risk reduction at Royal HaskoningDHV and has recently been selected to become a member of the UN Disaster Assessment and Coordination (UNDAC) emergency response teams