When is a sea wall a good idea?

The team’s objective is to come up with a multi-pronged proposal that would minimize storm-related damage as much as possible. “The optimal thing would be to have a suite of measures designed to work in concert to protect the coastline,” said Mandli.

Filling in the details
Using openly available New York City data, the scientists are mapping the footprints and critical elevation levels of all the buildings and infrastructure of Manhattan’s varied streetscape—including hospitals, subway entrances, and fire stations—with the goal of predicting how future hurricanes will impact communities at large.

“No one has really thought about the entire area with everyone included—all the agencies and all pieces of infrastructure, like the hospitals, the schools, the underground transportation system,” said Earth Institute faculty member George Deodatis, chair of Columbia’s Department of Civil Engineering and Engineering Mechanics.

The scientists are also taking into account the costs of such resiliency measures. Typically, every dollar spent on protection reduces damage-related financial losses by five to ten dollars. And, since it is often difficult to secure large amounts of government funding for coastal interventions, Mandli’s team may recommend a gradual installation of equipment every 30 years or so as new funds become available.

Besides, worsening storm and sea level rise conditions may trigger the need for more protection as the years pass, he noted. “We may only need a 5-foot wall now,” said Mandli, “but in 30 years, maybe we would need a 10-foot wall.”

Changing perspectives
To better understand the real-world effects of hurricanes on the different neighborhoods of southern Manhattan, the team is collecting input from state, city, and local officials. The findings from these outreach efforts—led by the National Center of Atmospheric Research (NCAR), a partner in the project—are supposed to help guide the team’s storm surge modeling.

So far, NCAR staff members Rebecca Morss and Heather Lazrus, the project’s co-principal investigators, have interviewed about a dozen leaders of the New York City and New York State Offices of Emergency Management and other government agencies. These officials have shared their views on the needs and vulnerabilities of their communities—explaining, for instance, how institutions such as hospitals depend on the power grid during emergencies, and offering recommendations on how to lessen risks from storm surge.

The team’s approach of collecting the officials’ responses and revising the scientific models and simulations accordingly is a crucial element of the project’s success, according to Mandli.

“The idea is, we have all these numerical and computational techniques of storm surge barriers – but if we just rely on those, we’re going to get an answer that might not be indicative of the true situation,” he explained.

“It is important for us to talk to people who are actually making the decisions and who understand the potential impact of storm surge on the ground,” said Lazrus. Morss and Lazrus plan to hold community meetings in select neighborhoods of the city next summer in order to gather local residents’ input and concerns as well.

The project is funded until 2019, thanks to a grant from the National Science Foundation’s Critical Resilient Interdependent Infrastructure Systems and Processes program. If the team can secure additional funding to extend the project until 2023 or 2024, Mandli and his colleagues will explore storm protection strategies for other U.S. coastal cities such as Tampa Bay, Miami, Houston, or New Orleans. To further their goal of broadening the project’s impact, the scientists have made their simulation software open-source and thereby available for use to anyone in the private or public sectors.

“The real intent here is try to provide this capability as broadly as possible, so that it’s applicable to anywhere in the world,” said Mandli.

Aline Reynolds is an urban planner and an urban affairs journalist. This story is published courtesy of Earth Institute, Columbia University