Rising Seas Threaten Historic Houses
People who own historic properties have long struggled to sensitively adapt them to changing times. They have come to terms with wiring and plumbing, once considered too disruptive for old buildings, and moved on to innovations like solar panels. On the theory that the greenest building is the one already built, architects are adapting historic structures to new uses altogether.
But these problems of adaptation pale beside an issue facing more and more historic houses and other properties: flooding from sea-level rise, especially in communities along the eastern seaboard, from Newport, Rhode Island, to St. Augustine, Florida, where the ocean has risen about a foot since the middle of the 20th century, and the rise is accelerating. Colonial-era neighborhoods find themselves awash during and after storms—or even when the moon is full. Scientists predict that, by 2100, seas will be three to six feet higher than they were in 2000.
So far, there are three main approaches to saving historic buildings from the ocean: moving them inland, armoring them with sea walls, or raising them on stilts. But these techniques can destroy the historic character that makes a property worth preserving in the first place.
When a single structure is moved to higher ground, a hole is left in the historic fabric and the structure’s notable relationship with the sea is lost. Armor drastically alters a site and inevitably results in damage to the natural coastline.
The most widespread tactic is elevation. Building codes enacted under the National Flood Insurance Program mandate raising buildings, sometimes by 20 feet or more. When buildings are elevated one by one (as is typical), a pleasant streetscape of once-harmonious rooflines can turn into an unsightly mess. “Lollipopping,” critics call it.
Many preservationists have fought putting a historic house on stilts, because that alters its foundation, porches, doors, and stairs, as well as its relationship to the street. (Properties listed in the National Register, or with other historic designations, are usually exempt from such requirements.)
But now, repeated flooding is prompting an urgent rethink, including consideration of an array of unconventional or even bizarre remedies.
The simplest steps are called “dry flood- proofing”—keeping sandbags at the ready in case of high water, or using basement sump pumps. Some owners are moving mechanical systems to upper floors. The Newport Restoration Foundation installed a space heater in one of its historic building’s basements—and bolted it to the ceiling.
More intriguing is “wet flood-proofing,” a kind of surrender to the water. With this strategy, the idea is to accept rising water, and make no effort to keep it out of basements. Some historic structures were actually built with stone foundations meant to allow water to flow in and out. If basement walls are impermeable, architects can fit flood vents into the walls, which let water in. After a flood, of course, water has to be pumped out. The technique has proved effective in New England, where many Colonial buildings are plank-on-frame construction and relatively impervious to minor flooding. In addition, many old buildings in the region were built with lime plaster, used since Roman times, that is durable and mold-resistant. And, if all else fails, basements can be converted to cisterns. So far, there are few deliberate examples of this—except in Venice, where lower floors of many buildings have been abandoned to water. (Unfortunately, when salt water dries in bricks and other materials, it leaves behind a host of problems.)
In addition, wet flood-proofing does prevent what could be a dangerous buildup of exterior pressure on basement walls, as water soaks the ground around them. This external pressure can be worsened when municipalities attempt to limit stormwater runoff by installing permeable paving on their streets, which has the unintended consequence of soaking the ground with even more water.
Whatever the merits of these approaches, there is a growing realization among coastal geologists, urban planners, architects, and preservationists that sea-level rise is a problem that must be tackled not building by building but rather with a community or regional perspective, taking into account not only a structure’s architectural significance, but its economic, social, or even sentimental importance.
And there needs to be discussion of what we mean by historic preservation. If a historic house must be elevated 10 feet or more, fitted with a cistern instead of having a basement, or actually made buoyant, has preservation gone too far? Have we irreversibly damaged its historic integrity?
Unfortunately, many historic properties threatened by sea level rise are beyond saving, or soon will be. Some preservationists are already urging their colleagues to think hard about the unthinkable: that some buildings must be relinquished. The National Parks Service (NPS), stewards of a large portfolio of sites in danger of sea level rise, is on the record for calling for this kind of effort. “Funding temporary repairs for resources that cannot, because of their location or fragility, be saved for the long term demands careful thought,” wrote Jonathan B. Jarvis, then director of the NPS, in 2014.
Today, historic preservation cannot be only about preserving buildings against change—especially if they are on the coast—but acknowledging that change is inevitable, and accelerating, and ways must be found to manage that. If a house is elevated in ways that destroy its historic character, something irreplaceable is already lost. But if analysis paralysis stymies action, much more that is irreplaceable will be lost as well.