Preservation Magazine, Winter 2021

Five Landscape Architecture Firms Think Big to Help Preserve the National Mall's Tidal Basin

Reed Hilderbrand's proposal for the Tidal Basin.

photo by: Reed Hilderbrand with Design Destill

An elevated pedestrian bridge is a key component of Reed Hilderbrand’s proposal for the Tidal Basin Ideas Lab.

Moving memorials, elevating walkways, restoring wetlands, and even transplanting the cherry trees themselves: These are some of the visionary proposals offered by five leading landscape architecture firms as part of the Tidal Basin Ideas Lab. The yearlong design initiative was organized to seek creative solutions to preserving—and reimagining—the Washington, D.C., landmark.

The Tidal Basin’s issues are myriad—and expensive to fix. Twice a day, the Potomac River floods the Tidal Basin, making sidewalks impassable and damaging the roots of the beloved cherry trees. As more people continue to enjoy the area, the National Park Service, which oversees the Tidal Basin as part of the National Mall, has struggled to keep pace with improvement costs. Total deferred maintenance estimates range between $300 million and $500 million, which doesn’t include an approximate $600 million in deferred maintenance for the entire Mall.

In 2017, the Trust for the National Mall (the nonprofit that advocates for the park) partnered with the National Trust for Historic Preservation, and the two groups eventually organized the Ideas Lab. Sponsored by a $750,000 grant from American Express and guided by the architecture firm Skidmore, Owings & Merrill, the Ideas Lab’s design firms—DLANDstudio, GGN, Hood Design Studio, James Corner Field Operations, and Reed Hilderbrand—presented their proposals in May of 2020. They were gathered into an online exhibition in the fall, which can be viewed at

Seri Worden, a senior field director at the National Trust, says the goal of the exhibition is to help raise awareness of the plight of the Tidal Basin while generating feedback on the design proposals and ways to improve visitor experiences. At the same time, users can submit their own memories of the area and thoughts on what the basin means to them. Stakeholders hope public support will help educate Congress about the need to authorize new spending for restoration projects.

Visitors to the online exhibition will find a series of illustrated slides and video presentations produced by the five firms. Each proposal calls for restoring the area’s wetlands in some way to help buffer flooding—but that’s where most similarities end. “We very deliberately chose a group of firms that would approach things differently, and they certainly did,” says Worden. “You can really see their originality and expertise come out, which makes the concepts fun and exciting to look at. It was exactly what I was hoping for.”

GGN of Seattle proposed building a freshwater tidal marsh with boardwalks, planting a floodplain forest along East Potomac Park, and relocating monuments as necessary to combat flooding.

Oakland, California’s Hood Design Studio presented its ideas through a series of graphic “novellas” offering suggestions on how to improve the visitor experience, with an emphasis on relating the area’s African American history. Hood’s other ideas include transplanting the cherry trees to a “cherry orchard” along a stretch of Independence Avenue, reimagined as a pedestrian promenade.

DLANDstudio of Brooklyn, New York, envisioned connecting cultural sites via newly developed ecological features. The Martin Luther King, Jr. Memorial would be moved to a protective jetty extending westward into the river, where it would be aligned symbolically with the Lincoln Memorial. A green “land bridge” of grass and cherry trees would stretch from the Jefferson Memorial across the Tidal Basin and north to the Mall. Traffic would be routed underground.

Reed Hilderbrand of Cambridge, Massachusetts, created a plan that keeps the Tidal Basin generally intact, while developing a “Washington Common,” a concept first proposed by the Senate Park Commission in 1902 but never realized. The idea calls for developing a lush natural playground of green spaces and protective wetlands, shaded groves, new pathways, and an elevated pedestrian bridge along the water’s edge.

James Corner Field Operations' proposal for the Tidal Basin.

photo by: James Corner Field Operations

James Corner Field Operations’ proposal included a new earthwork levee.

New York’s James Corner Field Operations outlined three possible scenarios. One idea was to simply let nature take over and curate the Tidal Basin and its monuments as a dystopian-like relic. Another scenario allows the floodwaters to create an island archipelago, with memorials and gardens connected by raised pedestrian bridges. The final, more realistic idea preserves the basin by constructing a protective earthwork levee along the Potomac.

Sean Kennealy, deputy superintendent of the National Mall and Memorial Parks, recognizes that many of the ideas are purely aspirational in nature, but he’s excited by what he sees. “The presentations are provocative and definitely spurring conversation,” he says. “People should realize that by no means are these final decisions on what the Tidal Basin will be transformed into, but just an important first step.”

Kennealy says the Park Service will consider all ideas as it moves ahead with a master plan for the area in 2021. He says incremental actions—like shoring up the seawalls and widening pathways—are potential changes that could take place within the next decade. But relocating the cherry trees and creating island archipelagos?

“These ideas are certainly long view,” says Teresa Durkin, executive vice president of the Trust for the National Mall. “I see the initiative as just getting people to think differently about how we treat these landscapes, how we take care of them, and how they need to evolve. These designers have given us visions for the future—just like [Washington planner Pierre Charles] L’Enfant did for the whole city.”

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Joe Sugarman lives in Baltimore and is a frequent contributor to Preservation magazine.

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