Should I Stay or Should I Go? Predicting the Benefits of Coastal Retreat in the Wake of Sandy

Hurricane Sandy's massive destruction, as well as the impacts from other recent storms, have shifted public discussion about sea level rise and climate change from the theoretical to the practical. New York Governor Andrew Cuomo was widely quoted with the following comment after the storm: "Anyone who says there is not a change in weather patterns is denying reality” (Viekland, 2012). It was followed by Mayor Michael Bloomberg's own statement: "While the increase in extreme weather we have experienced in New York City may or may not be the result of climate change, the risk that it might be - given this week's devastation - should compel all elected leaders to take immediate action" (Bloomberg, 2012).

The devastation wrought by Superstorm Sandy has clearly galvanized public discourse about the impact of climate change on coastal communities, and dramatically increased awareness of vulnerability to coastal hazards amongst citizens and officials alike. As the Intergovernmental Panel on Climate Change (IPCC) noted in 1995, our shoreline communities are amongst the most at risk. They observed that by 2100, predicted rates of global sea level rise could lead to flooding of low-lying coastal regions and wetlands, more frequent storm surges, and worsening beach erosion (IPCC, 1995).

In a prescient observation, Titus (1984) stated: "Although sea level is not expected to rise rapidly until after 2000...communities may have to consider its consequences much sooner. After the next major storm, in particular, homeowners whose properties are destroyed will decide whether and how to rebuild; and local governments will decide whether or not to let all of them rebuild, and which options are appropriate to address the storm-induced erosion."

Titus' prediction became reality when New York Governor Cuomo announced an unprecedented initiative to use $400 million of the $51 billion the U.S. Congress approved in disaster relief funds in late January 2013 to buy out up to 10,000 homeowners located in the 100-year floodplain. The innovative and unprecedented plan provides for a bonus for homes in “highly flood-prone” areas as well as a doubling of the bonus for areas where an entire block agrees to sell to the state. Residents in the most vulnerable areas will be able to sell to the state even if their home has not been damaged more than 50% by Sandy. In the undamaged areas, a 10% bonus would apply if an entire block sold. The state would then turn these lots into dunes, wetlands, parks and other natural buffers. This voluntary buyout and resettlement program would allow for a degree of autonomy in decision-making about rebuilding personal property or retreat, in contrast to typical patterns of displacement or automatic incentivizing to rebuild.

By allowing restoration of natural defenses and coastal habitats to protect existing inland communities while reducing the cost of repetitive losses and the risk to the health and welfare of citizens, the plan has the potential to be a trendsetting and transformative initiative, showing the world the way toward ecological and human community resilience. Its relevance is perhaps of even greater significance considering the high population densities of coastal populations in vulnerable regions worldwide - particularly in South Asia, East Asia, the Pacific, and Latin America and the Caribbean.

Moreover, his plan suggests a shift in the impulse to defend unsustainable settlement patterns. 10,000 homes were substantially damaged by Sandy, and the state expects 10 to 15 percent to be sold to the state.

The plan to buy up houses, however, as the Governor was quick to point out, is completely voluntary. The voluntary nature of the program means that it may have significant implementation hurdles. There is the potential for what is called "checkerboarding," as happened in New Orleans post-Katrina, where some homes are sold and others remain, which would substantially reduce the value of the land for flood protection and increase infrastructure provision costs to the the neighbors who remain.

However, decision to launch New York's program was made without a very clear sense of the costs and benefits of strategic retreat versus a protection strategy.

In this project, we develop a methodology to determine whether buying out or rebuilding will lead to better outcomes for a community's future, and test the methodology using GIS based natural hazard loss estimation software. Based on hypothetical land-use redevelopment schemes in the wake of Hurricane Sandy, we estimate potential losses from future storms in a number of projected climate change scenarios.

The GIS-based natural hazard loss estimation software package HAZUS developed by the Federal Emergency Management Agency (FEMA) is used alongside NOAA's Coastal Adaptation to Sea Level Rise Tool to estimate damage of future climate change scenarios.

The results will help demonstrate the cost savings and benefits to communities that choose to redevelop with environmentally sound, less-intensive land use patterns in vulnerable areas.

The estimation is piloted for specific New York City coastal neighborhoods including New Dorp Beach and Midland Beach, Staten Island, as well as Red Hook, in Brooklyn, to assess the areas and systems which are most vulnerable to coastal flood impacts.

We expect to find that strategically retreat will reduce damage and loss of life given future climate change in low density communities, but that at certain density thresholds, the only economically viable option is protection.

Keywords: Sea level rise, Storm surge, Redevelopment, Coastal flooding, Climate Change