Thought Leadership

Barriers, Loss, or Transformational Retreat? What is the right approach for your threatened coastline?

September 21, 2021

By Rebecca Verity, Adaptation Planner, GEI Consultants

We’re going to build back, bigger and stronger than ever before.”

We’ve heard this mantra over and over. We’ve heard it from Louisiana Governor Blanco after Hurricane Katrina, from President Obama after Hurricane Sandy, and from Texas Senator Ted Cruz after Hurricane Harvey. New York City is also building “bigger and better.” The National Oceanographic and Atmospheric Association (NOAA) reports that U.S. high-tide flooding broke records in the past year, and predicts that damaging flooding will be common along most U.S. coasts by 2030.  In the face of rising seas and larger storms, we are often presented with only two options: Build larger barriers or lose our coastal communities like children losing sandcastles to the tide.  But history proves that we are a creative bunch, and our options are much more nuanced.

Manhattan has broken ground on a $1.45 billion flood barrier project[1] to protect 110,000 East Side residents from flooding by adding coastal floodwalls and raising the East River Park by eight to nine feet.  It’s part of a $20 billion plan to protect lower Manhattan from storms like Sandy. That price tag buys the city time: it is designed to protect from flooding for 30 to 80 years, after which, taller barriers or new approaches will be needed.

It’s important to understand that barrier projects, such as New York’s East Side Coastal Resiliency Project, protect specifically against flooding from the sea. They do not stop floods from inland storms.  Torrential rain, such as the rain brought by Hurricane Ida on September 2, 2021, can be trapped behind sea walls and levees.  Such barriers usually have pumps and other drainage built in. New York’s planned system will feature such pumps. But the question remains:  would New York’s planned pumps have kept up with the unprecedent torrent that fell September 2nd?

One option for the coastal city of Monterey includes the barrier of a sea wall.

Building back “bigger and stronger” isn’t always the right solution. As seas rise and storms grow, some coastal communities have been forced to the opposite direction: retreat.  Sometimes, as in Newtok Alaska, an entire community relocates together.  Sometimes, as in Ocracoke, North Carolina, retreat happens in a slow trickle of emigrees, as the costs to rebuild become too daunting and the risks of remaining too high. Around the country, FEMA is buying out properties subject to repeat flooding. It is a financially savvy move that both reduces the federal costs of repeated rebuilds and enables residents to invest those dollars in safer locations.

In coastal areas with either high resources or high determination, and at least some high ground, flood-adapted communities may become the norm. What is a flood-adapted community? Adaptation-focused city planners are envisioning floodable businesses and parks, with self-rising flood gates, flood-proofed electrical infrastructure, elevated or floating homes.

This type of transformational retreat – where dry land is ceded to water and communities continue to thrive – provides a kind of middle ground, supporting coastal lifestyles while reducing risk and loss.  In California, one city has identified a forward-thinking approach to transformation.

Monterey’s Innovative Opportunity

Along California’s Central Coast, where the potential for devastating earthquakes lends an extra layer of risk to living behind coastal flood barriers, the City of Monterey has spent two years studying their sea level rise options. Perched on the edge of a stunning marine sanctuary and extolled by Steinbeck, Monterey is one of the most storied, picturesque, and beloved of California’s coastal cities.  It is also a critical regional transportation corridor. With few alternate commute options, more than 57,000 cars commute daily through this city of less than 30,000 residents. The only road currently large enough for that density, the city’s primary commute corridor, is also the lowest and most flood-prone. Without action, that corridor will be lost to rising waters in this century.

A city of hills, most of Monterey rises steeply on granite cliffs above the bay. Flood models indicate that only a small portion of its acreage, centered in downtown, is threatened in this century. The geography that adds to Monterey’s beauty is what makes adaptive retreat possible in a way that is not possible in flatter coastal communities.

Throughout 2019-2020, I worked with the city and their long-term transportation planners at Kimley-Horn, to explore two alternate visions: the first would protect the existing downtown behind large coastal barriers – this is the “building bigger” option. The second alternative would create a new downtown waterfront by carefully transforming an existing downtown lake and the adjacent shoreline into a sheltered arm of the rising bay.

An adaptive retreat would bring the bay into the heart of downtown Monterey.

Under the barrier scenario, existing beaches would eventually be lost, and coastal access would require paths over new levees or seawalls. Adaptive retreat, on the other hand, would bring the bay into the heart of downtown, adding more than two new miles of coastal access in the city center.  In this scenario, retreat could revitalize and enhance downtown, restore a degraded aquatic lake ecosystem, and build a transportation network more suited to resident’s needs. Along with new beaches and wetlands, bike and pedestrian paths would be built, sheltered swimming and boating areas could be created, and additional water-front dining and shopping could open economic opportunities for residents.

Levees are still recommended to protect portions of critical roadways but, under the adaptive retreat scenario, these areas are relatively small. Issues of cost for either option are critical, as are issues of equity. Many of the City’s homes and services for lower income residents lie in the flood zone. Barriers would place the most vulnerable at highest risk; adaptive retreat would require relocation for those with the fewest resources. Both sets of challenges are significant, and our strong recommendation is that finding equitable solutions be centered in either approach.

In the face of ever larger floods, building “bigger and better” makes an excellent slogan.  But, for the safety of residents, and the long-term vitality of coastal communities, building smarter makes a lot of sense. The recipe to success will take creativity, transparency, honesty, collaboration, community, and of course, funding. To learn more about climate adaptation, or to discuss your own project needs, contact Rebecca.


Adapting a Threatened Transportation Road Network to Sea Level Rise, Rebecca’s project for the City of Monterey in partnership with Kimley-Horn, was recently awarded the Outstanding Climate Document Award for 2021 at the annual conference of the Association of Environmental Professionals (AEP).