Geneva, 4 November 2013
The resilience of the New Yorkers affected by Hurricane Sandy was put to the test a year ago. The physical violence of the storm surge delivered a stunning blow while the flooding that followed brought the state to a halt. Too much water in the wrong place, at the wrong time spells catastrophe.
Resilience. The dictionary defines it as “the capacity to recover quickly from difficulties”. The resilience of the New Yorkers affected by Hurricane Sandy was put to the test a year ago. The physical violence of the storm surge delivered a stunning blow while the flooding that followed brought the state to a halt. A fifth of the city’s land was flooded and large portion of the city was enveloped in darkness due to power failure. Around 150,000 homes were destroyed and over US$ 30 billion of damage was inflicted.
However, New Yorkers weren’t the only ones whose resilience was tested that year. Despite 2012 being classified as a “moderate year” in terms of overall economic damage caused natural disasters, flooding and storms are wreaking more havoc than ever before. According to the Worldwatch Institute
, of the 905 documented natural disasters in 2012, 45 percent were storms and 36 percent were floods. Worryingly, for the first time in history more people live in urban centres than in rural areas and many mega cities are located on the coast or close to rivers.
As a result, the economic and human costs of storms and flooding has risen significantly over the past few decades. According to Swiss Re, a global reinsurer, losses due to flooding have increased from US$ 1-2 billion to US$ 14 billion in just under 40 years. We are more vulnerable to flooding events than ever before. Too much water in the wrong place, at the wrong time spells catastrophe.
Wetlands, storm surges and flooding
Wetlands will slow down the progress of a storm surge, and are effective buffers for for weaker and faster-moving storms. A simulation study revealed that sufficiently wide and tall vegetation canopy (such as mangroves) can reduce inundation on land by 5 to 40 percent depending on the type of storm and vegetation. Coastal wetlands in the USA are estimated to currently provide US$ 23.2 billion a year in storm protection services alone.
Wetlands also act as natural sponges that trap and slowly release surface water, rain, snow melt and flood water. One acre of wetland can typically store three-acre feet (one acre of land under three feet of water) or one million gallons. Trees and other wetland vegetation reduce the speed of flood waters. Flood plains in the lower reaches of rivers allow water from heavy rainfall or spring snow melt to spread slowly. The combined water storage and braking action helps lower flood height and reduces erosion.
This free storm and flood insurance provided by wetlands has not been valued enough. Coastal wetlands in the eastern United States are being lost at twice the rate they are being restored. The loss of one hectare of this wetland type corresponds to an average of US$ 33,000 in subsequent storm damage costs.
The flood protection services of wetlands are also being undermined by unsustainable development. For example, the hardwood-riparian wetlands along the Mississippi River once stored 60 days of flood water. Now they store only 12 days of flood water as most of them have been filled or drained. Flood plains around the world have been drained and cut off from their rivers by artificial embankments. This has drastically reduced the surface area for flood water to spread. As a consequence floods are deeper and a breach in artificial embankments can have catastrophic consequences.
The irony is that the very urban developments for which the flood plains were drained and filled are now the most vulnerable to flooding. The residents in these areas pay a very high home insurance premium as they have been classified as high-risk flooding zones. Worst of all they have to live with the possibility of having all their possessions and memories obliterated by a surge of water.
Wetlands as natural infrastructure
The spate of storm and flooding events in recent years have resulted in a growing interest in the value of wetlands as natural infrastructure within integrated flood protection systems and coastal protection plans. The NYS 2100 Commission tasked with improving the resilience of New York State post-Sandy states in its report that “A green infrastructure approach emphasizes the use of solutions that maintain and support services provided by natural systems, such as wetlands and dunes that can serve as natural buffers against storm surges and complement efforts to build new traditional infrastructure to protect communities.”
The failure of dykes in New Orleans during Hurricane Katrina left the city unprotected and exposed the limitations of relying completely on a “silver bullet” solution. In addition, massive engineering solutions such as harbour storm surge barriers costs billions of dollars to build and are expensive to operate and maintain.
These risks and limitations have resulted in a change in mindset among city officials who once favoured massive grey infrastructure projects. The plaNYC report for a stronger and more resilient New York states that “the City believes that the right approach to coastal protection is an integrated system of discrete coastal projects, that together would constitute the elements of a multilayered approach.” Instead of opting for a one-size-fits-all engineering solution, the report recommends that coastal protection measures should be designed to match the risks facing a given area. For example, it identifies specific areas that would benefit from the wave-attenuation properties of wetlands, oyster reefs and coastal forests.
However, we do not have enough information to accurately estimate the degree of protection different wetlands provide from storm surges and floods. This is a gap in knowledge and previous studies based on simulation models need to be validated using real world data. Scientists and city officials should allocate resources to what could be a cost-effective solution for making cities more resilient. After all, many lives may depend on it.
To learn more about the diverse values of wetlands, visit TEEB for Water and Wetlands
About the Author
Anand Chandrasekhar, is based in Switzerland and has a Masters in Conservation Biology from the University of Kent, UK and a Bachelors in Forestry from the Tamil Nadu Agricultural University, India. His experience extends to a wide range of environment issues including species conservation, environmental law and policy, natural resources governance, climate change and carbon markets. He now specializes in science and environment communications and enjoys developing thought-provoking content and challenging conventional thinking.
Disclaimer:
The views expressed in this blog are purely those of the authors and do not necessarily reflect the views of TEEB and should not in any circumstances be regarded as stating an official position of TEEB.