College students volunteer with Habitat for Humanity in New Orleans. (Gerald Herbert/AP)

Walter Isaacson is president of the Aspen Institute and a member of Service Year Alliance's Leadership Council. He was vice chairman of the Louisiana Recovery Authority after Hurricane Katrina.

Flying into my home town of New Orleans on a National Guard helicopter shortly after Hurricane Katrina's floodwaters receded 12 years ago, I saw devastation so great that I wondered how many of the hundreds of thousands who fled — nearly half the population — would ever return. I had no idea then that a tragedy that caused more than $100 billion in damage and took 1,800 lives would lead to the rebirth of our city and bring it back even stronger.

A little-known part of the story of the rebirth of New Orleans is the role national service played.

I was on that helicopter because I had been asked to serve as vice chair of the Louisiana Recovery Authority. Early on, I met with a group of Teach for America corps members. Because it was unclear whether the school system would reopen, they had been given the choice to relocate. Instead, they stayed in New Orleans and took on a grand mission: to build a new type of school system that would be better than the old one. Instead of shrinking, the Teach for America corps quadrupled in three years.

Others stepped up in similar ways. Half a million Americans made the trip to the Gulf of Mexico to do what they could in person. Local nonprofits were among the institutions devastated by the floods, and the arrival of this many people could have added to the stress on the city. Instead, teams of AmeriCorps members from the National Civilian Community Corps relocated to New Orleans immediately to lead volunteers who were gutting houses, carrying out water-soaked sofas and carpets, knocking down drywall, and removing mold — often in 100-degree heat. In the years that followed, AmeriCorps members restored nearly 14,000 homes and built 1,600 others.

Tulane University, one of the city's finest institutions, closed for four months after Katrina. When it reopened, it became an engine of revival to help make the city better than before. A major part of that effort was Tulane's Center for Public Service, established in 2006 by then-university president Scott Cowen as part of the university's Renewal Plan. Tulane became the first and only major research university in the country to integrate a public-service graduation requirement into its undergraduate curriculum, and it created one of the largest campus-based Volunteers in Service to America (VISTA) programs. This program enabled hundreds of graduating students to take on leadership roles in the community to rebuild the capacity of community organizations.

Other community institutions were also wiped out. For example, many local lawyers were displaced, the legal infrastructure in many communities eliminated. That didn't stop the 125 Equal Justice Works attorneys and law students who answered the call to address Katrina-related legal needs — the evictions, illegal foreclosures, fraud and insurance disputes that abounded, along with bankruptcies, child custody disputes and issues arising from lack of property ownership documentation.

Katrina helped accelerate a deeply American instinct: to help neighbors and nation in a time of great need. More than 40,000 national service participants have served in New Orleans over the past decade. National service not only provided badly needed short-term help but also played an essential role in calling many of its best and brightest citizens back after Katrina and in recruiting new talent to New Orleans. While AmeriCorps members made a profound difference through their service year, these diverse teams brought something even bigger: powerful innovations that have transformed almost every aspect of the region.

New Orleans has become a magnet for education entrepreneurs, many of them former Teach for America corps members. Before Katrina, the city's school district was second from the bottom statewide in math and reading scores. Orleans Parish students now score on par with the state average, and graduation rates and standardized test scores have risen.

Others who came to serve for a year stayed to start new organizations. Robert Fogarty left a career in finance in New York to join VISTA in New Orleans and went on to found Evacuteer, which recruits and trains evacuation volunteers. Angela Davis, a Mississippi native drawn to New Orleans to serve in AmeriCorps, founded Hagar's House, a shelter for women and children. Others took on leadership roles with existing organizations. They are a big reason many call New Orleans one of the nation's most entrepreneurial cities.

Today, Houston faces many of the same challenges New Orleans faced, and communities in South Florida are bracing for the worst as Hurricane Irma approaches. While many lessons can be gleaned from our experience after Katrina, the vital role of national service is an especially important one. Retired four-star Gen. Stanley McChrystal has called for every 18- to 28-year-old to perform a "service year" to give something back to their country, meet public needs and understand what it means to be a citizen.

While every young American ought to have the opportunity — indeed the expectation — of a service year, we can start by bringing national service at scale in Houston and in every community overwhelmed by challenges it cannot tackle on its own. This has been the American instinct since our founding: to serve others and in turn strengthen our nation.