Pizzanello volunteered that she’d sent one of her clients, living in a below-flood-elevation house on a slab and paying $3,200 annually for N.F.I.P. coverage, to talk to Vernon. Short of options, they looked into private insurance. The lowest quote that came back was $22,000 a year. It was one of those raise-or-raze situations, Vernon told the gathering, saying, “Elevation certificates are literally about tenths of feet.”

Spend a few days talking about floods and real estate in Norfolk, and you’ll quickly learn the importance of even tiny inclines. Locals know where, on what appears to the uninitiated to be a flat street, to park their cars to keep them from flooding past the axles when the wind pushes the tide up. Landscapers build what are essentially decorative earthen dikes around houses. When I asked one man how close storm and tidal surges come to his front porch, he pointed at the bricks under my feet, which I had taken for the wall of a flower bed. “You’re actually standing on a bulkhead,” he said.

In the coming decades, these fine distinctions will mean little, as the risk of flooding becomes the certainty of it. The operative measurement for rising waters in Norfolk is not inches but feet — as many as six of them by the end of the century, according to the Army Corps of Engineers, though estimates vary. City planners are forthright that they’re preparing for a future in which parts of the city do not survive. “We absolutely cannot protect 200 miles of coastline,” George Homewood, Norfolk’s planning director, says. “We have to pick those areas we should armor, and the places where we’re going to let the water be.”

Norfolk now mandates that new construction be built three feet above current base flood elevation (as if the houses were boats, this distance from the waterline is called freeboard), and 18 inches above what Homewood says is “euphemistically known as the 500-year floodplain.” But Norfolk is an old, established city, where changing new construction can only get you so far. In 2008, the city hired a Dutch engineering firm, experienced with life below sea level, to help develop a plan for adaptation. The firm suggested $1 billion in changes, more than half of which would go to simply updating existing infrastructure.

Like insurers, residents are playing a game of risk and timing. “Adaptation is a range,” says Fred Brusso, a former city flood manager. “Do you need to just move your car? Do you have to put your washer and dryer on cinder blocks? Or do you need to get the heck out of town?” Sean Becketti, the chief economist for Freddie Mac, cautioned in a report last year that economists aren’t sure if coastal property values will decline gradually, as the life expectancy of homes shrinks, or precipitously, “the first time a lender refuses to make a mortgage on a nearby house or an insurer refuses to issue a homeowner’s policy.”

Skip Stiles, the executive director of the local nonprofit Wetlands Watch, took me on a tour of frequently flooded areas of Norfolk — when waters are down, Stiles uses rusty storm drains and marsh plants growing in yards and medians to show where they’ve been — and pointed out buildings that had been elevated. Often their awkwardness made them obvious: ordinary, colorful houses perched uncomfortably atop walls of bare concrete blocks. While FEMA does pay to elevate risky houses, it struggles to keep up with demand: Wetlands Watch compared the number of people on the FEMA waiting list in Norfolk with the number of houses raised in a year, and concluded that it would take 188 years to complete them all. By then, of course, waters would be far higher.

This is the hardest reality to discuss, Stiles said, and a reason flood insurance is serving as a kind of advance scout into a more difficult future. “When you go out to the end of the century, some of these neighborhoods don’t exist, so it’s hard to get community engagement,” he said. “Nobody wants to talk beyond where the dragons are on the map, into uncharted territory.”