Floodwaters are gone but not forgotten: lessons learned from Sandy

Thumbnail image for figure_1_basemap_highres.jpg

There’s a lot in the news about climate change and how it’s affecting communities today.

There’s a new Intergovernmental Panel on Climate Change – also called the IPCC – report that details the effects of climate change on human and natural systems around the world, both now and in the future. In the next month, the Third National Climate Assessment report will be launched, and will describe the effects of climate change already observed here in the US, and trends anticipated for the future.

We can help ourselves to be better prepared for a changing climate, by incorporating the insights science offers us about what kinds of changes to expect – for example, so coastal cities can plan and take better steps to prepare for changing risks from storm flooding.

Today, NRDC is releasing an issue brief, Preparing for Climate Change: Lessons Learned for Coastal Cities from Hurricane Sandy that highlights the human cost when we don’t take climate change’s effects into account.

According to NRDC’s new mapping analysis, the total area flooded by Sandy in the five boroughs of New York City was 65 percent bigger than FEMA’s flood maps led residents and city officials to expect. We took a closer look at some of the people and places that were outside FEMA’s then-existing 100-year floodplain, which had been mapped in 1983. NRDC’s new mapping analysis found that among those people not included in FEMA’s then-existing floodmaps, but were inundated nonetheless during Hurricane Sandy, were: 

  • Nearly 290,000 New Yorkers in total
  • Nearly 90,000 people with limited economic means to recover
  • More than 59,000 people who were likely to need help to get out of harm’s way (specifically, more than 16,000 children under age 5, and more than 43,000 people over 65 years old)

A number of the inundated buildings were providing services for children, the elderly and the sick, or serving other important functions to keep the city operating safely. These facilities were flooded during Sandy but were not previously identified by FEMA as being in the 100-year floodplain:

  • 80 schools
  • 74 daycare centers or Head Start facilities
  • 28 public housing buildings, home to over 61,000 residents
  • 22 residential facilities providing social services for adults, families or children (such as homeless shelters, group homes and assisted living facilities)
  • 18 hospitals or nursing homes
  • 9 senior centers
  • 4 wastewater treatment plants, causing 600 million gallons of sewage to overflow into area waterways


The areas shown in red on the NRDC map shown here were outside the FEMA 100-year floodplain at the time Sandy struck, yet were inundated by Sandy floodwaters.

The 100-year floodplain maps are really important documents, applied as default points of reference for planning and protection in coastal and waterfront communities. NYC Mayor Bloomberg convened a Special Initiative on Rebuilding and Resiliency (SIRR) after Sandy. SIRR’s June 2013 report explained that, 

“Hurricane Sandy demonstrated the importance of regular coastal updates to FEMA’s maps… about 60 percent of all buildings and more than half of the residential units in areas that Sandy inundated were outside the 100-year floodplain…In these areas, not only were residents unaware of the risks they faced, but the buildings in which they lived and worked had not been subject to the flood-protective constructions standards that generally apply within the floodplain (p.23, June 2013 SIRR report).”

And even now, the new preliminary floodplain map updates proposed for New York City in December 2013:

  • Don't include future climate change effects, especially continuing effects of rising sea levels
  • Don't reflect sea level rise that has occurred in the past decade, because data is from 1983-2001;
  • Have maps based on historical flooding/storm events, but not information from Hurricane Sandy.


Thumbnail image for HurricaneSandyNYC_m_1206.jpg

Waves crash ashore near the Verrazano Bridge in Brooklyn, ahead of Sandy. (Source: caphotosnewyork/Flickr)

The task at hand for flood-vulnerable coastal communities is to apply the most up-to-date information available on current sea level rise, on recent storms and floods like Sandy, and on future projections of climate change effects on flooding- with the goal of creating the very best improved maps. My NRDC colleague Rob Moore has blogged on FEMA’s opportunity to enhance coastal protection and climate resiliency by this kind of comprehensive floodplain map updating.

Sea level at the Battery in New York City has already risen a little over a foot since 1900. Climate change will speed this effect in years to come: in 40 years, sea level in NYC is likely to rise another 11 to 24 inches, with 31 inches possible by the 2050s, according to the New York City Panel on Climate Change. But the state of FEMA’s flood maps is far more than just a New York City story. By 2025, an estimated 75% of Americans will live in coastal counties, and with climate change making sea levels rise, higher storm surges will affect many millions of people across the country.

In years to come, we don’t want to look back on these opportunities and say, “We should have done better.” We encourage FEMA to include the effects of climate change in their flood mapping efforts today, and address the challenges of climate change preparedness in a way that stands to save lives, save dollars, and create healthier, more secure communities.