Within the next 30 years, the United States can expect to see a one-foot rise in sea levels even if CO2 emissions went to zero overnight[i]. This is because more than 93% of the heat humans have already generated is trapped in the oceans where it will linger for centuries[ii]. Over the next seventy to eighty years, sea levels may go up by 7 feet based on how quickly the warming waters melt the Arctic ice sheets, rates of land loss, and ocean circulation changes[iii].
For every foot of rise, roughly 100 feet of shoreline will be flooded[iv]. The consequences could be catastrophic for many of the 130 million people who live in a coastline community – more than 40% of the U.S. population[v]. They should expect more than ten disruptive flooding events per year by 2050[vi].
A similar fate is in store for communities living in the American West. Almost 60 million homes are within less than a mile of a wildfire-prone area[vii]. Those numbers will continue to grow as the increased intensity and duration of heatwaves and drought conditions create a risk of bigger, more frequent blazes.
These communities can respond in one of three ways: they can resist, accommodate, or retreat. Resist options include hard infrastructure like seawalls, levees, and dikes. Accommodate options include elevating homes, building reinforcements, or early warning systems. Retreat entails physically moving people away from the source of risk, like moving out of forested areas or away from coastlines and further inland to a more elevated surface. While the three options can be complementary, there is little time to act and limited resources.
This paper looks more deeply at the option to retreat. A burgeoning area in emergency response and disaster relief planning is the concept of “managed retreat” or “managed relocation” – the purposeful and coordinated movement of people and assets out of harm’s way.
This concept has been applied in environmental relocations that have occurred throughout American history, including in response to Californian acid spills and flood damage across the Gulf Coast in Florida, Louisiana, and Texas.
I set out to answer the question: what are the most efficient and cost-effective methods to encourage state and local governments as well as at-risk households to proactively retreat?
I begin by characterizing the most common environmental threats posed by climate change that communities will be retreating from and what the barriers are to successful managed retreat. Then I will conduct four case studies of cities or counties implementing managed retreat programs against sea-level rise, coastal erosion, and flooding: (1) King County, Washington, (2) Charlotte-Mecklenburg County, North Carolina, (3) Austin, Texas, and (4) Queens, New York.
A comparative analysis will be done on these case studies to assess their outcomes, cost-effectiveness, and policy tradeoffs. Finally, I conclude with recommendations and next steps for policymakers who are looking at implementing managed retreat policies.
Ultimately, certain areas will be under water or smoldering in ashes no matter what we do. People in those areas are already, and will inevitably, retreat. Whether or not it is done in a managed and coordinated way is a different question. Despite the name, “managed retreat” should not be thought of as accepting defeat. Rather it is a chance to live to fight another day. In the words of Marine Corp General Oliver Smith, “Retreat, hell! We’re not retreating, we’re just advancing in a different direction.”[viii]
[i] National Oceanic and Atmospheric Organization (NOAA), “U.S. coastline to see up to a foot of sea level rise by 2050”, February 15th, 2022, https://www.noaa.gov/news-release/us-coastline-to-see-up-to-foot-of-sea-level-rise-by-2050
[ii] Patterson, Brittany. “How Much Heat Does the Ocean Trap? Robots Find Out,” Scientific American, October 18th, 2016, https://www.scientificamerican.com/article/how-much-heat-does-the-ocean-trap-robots-find-out//
[iii] Ibid. 1.
[iv] Albert, Mark. “Why a 1-foot rise in sea level has a bigger impact than you think,” WCVB Boston, February 25th, 2022, https://www.wcvb.com/article/sea-level-rise-forecasting-our-future/39135613#.
[v] National Oceanic and Atmospheric Organization (NOAA), “U.S. coastline to see up to a foot of sea level rise by 2050”, https://oceanservice.noaa.gov/facts/population.html.
[vi] National Oceanic and Atmospheric Organization (NOAA), “Global and Regional Sea Level Rise
Scenarios for the United States”, February 2022, https://aambpublicoceanservice.blob.core.windows.net/oceanserviceprod/hazards/sealevelrise/noaa-nos-techrpt01-global-regional-SLR-scenarios-US.pdf.
[vii] Sommer, Lauren, “Millions Of Homes Are At Risk Of Wildfires, But It’s Rarely Disclosed,” NPR, October 21st, 2020, https://www.npr.org/2020/10/21/924507691/millions-of-homes-are-at-risk-of-wildfires-but-its-rarely-disclosed#:~:text=Almost%2060%20million%20homes%20were,blazes%20in%20the%20American%20West.
[viii] HistoryNet, “‘KEEP PUNCHING’: SIX MILITARY QUOTES TO GET YOU THROUGH THE WEEK,” March 27th, 2020, https://www.historynet.com/keep-punching-six-military-quotes-to-get-you-through-the-week/#:~:text=%E2%80%9CRetreat%2C%20Hell!,the%20Battle%20of%20Chosin%20Reservoir.