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Bloomberg's plan to fortify NY against #climatechange storms

Image: Nicola Romagna flickr/creative commons

This week,  New York City mayor Michael Bloomberg decided the best way to deal with sea level rise from climate change is to spend $20 billion fortifying the city. It was the political equivalent of Gandalf’s famous ‘you shall not pass!’ in Lord of the Rings.

So what will spending the amount of the Hurricane Sandy cleanup bill on fortifying for the next giant storm that’s inevitably coming do for the city, and will it work?

There’s a whole raft of initiatives which include sensible suggestions like working with FEMA to create better flood risk maps – which are available online if you’re a New York City resident and would like to check whether you should sell your house now, before everyone else works out it’s going to get flooded more often and your property value bottoms out.

There are also some more fanciful proposals like better coordinating between State, Federal and City government for more up to date localised climate impact projections, which, in case Mayor Bloomberg hasn’t checked lately, will include having to convince most of the GOP that climate change exists...

As we roll along towards 2050 (oh, it will come sooner than you think) there are areas of New York City that could start to have the displeasure of daily or weekly tidal flooding, so the city has a combination of initiatives that it will put in place to try and make sure that Manhattan avoids feeling like Venice twice a day as the tide comes in.

High tide in Venice – coming soon to Manhattan? (image: Roberto Trm, flickr/creative commons)

The City is going to reinforce some areas with levees, floodwalls and bulkheads, combining that with outer barriers to slow waves before they hit the shore (similar to the Thames barrier in London). This will be together with offshore breakwaters, tide gates, dune restoration and the recreation of wetlands and reefs to give the floodwaters somewhere to go. The city also wants to try ‘beach nourishment’ -- which is a fancy name for trucking back the sand that was washed away from the beach. This can get expensive however; as Queensland Australia has found now that the local government is spending $30,000 per day to truck sand back to the beach.

‘Will it work?’ is a question that can’t be answered until the next Sandy (or worse) comes along, at which point we all hope that the plan was successful. As of 2010, there were 400,000 people living within the floodplain of New York City. With sea level rise, it’s estimated that this number could increase to 800,000 people and also include 97% of NYC’s power plants.

The report doesn’t shy away from the impacts that New York City will be facing from climate change, pointing out that sea levels around NYC could increase by 76cm (2.5ft) or more by mid-century, especially if "the polar ice sheets melt at a more rapid rate than previously anticipated".

Funny you should mention that, Mayor Bloomberg. It’s possible we could have an ice-free Arctic this summer, which is at least three years ahead of the worst case scenarios. While an ice-free Arctic won’t add volume to the oceans, what it does do is slow the jet stream allowing for more weird weather patterns to collide with each other in the same way Hurricane Sandy happened.

Parts of NYC at risk for future flooding (PlaNYC report)

Reinsurance firm Swiss Re worked with the city to measure the cost benefit analysis of the plan and found that a storm like Sandy occurring in the context of climate change in 2050 could end up costing $90billion in damages rather than the $19billion bill Sandy left, which almost makes the PlaNYC project look cheap.

New York City does have one advantage for the plan to work better than it would elsewhere – geology. New York is built on top of pretty solid bedrock covered by glacial deposits which means the rocks are not very porous. So when New York City builds a levee or floodwall to keep the rising seas out, it’s likely the water will stay out compared to somewhere like Miami which is built on top of very porous limestone which means even with a floodwall, the floodwaters will simply bubble up from underground. Slightly terrifying.

New York City’s report is the first very proactive adaptation plan by a large wealthy city. As the more serious consequences of climate change become more apparent, many cities will follow suit to try and adapt to our new normal. 

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