Rebuilding the Tidal Basin Seawalls: Saving a Sinking Landmark

A flooded path at the Tidal Basin. NPS.

A landmark under water

Stand on the shore of the Tidal Basin in Washington, D.C., among the cherry blossoms and monuments, and you are looking at one of the capital's defining scenes — and at a problem beneath it: aging seawalls worn down by time, rising seas and poor drainage.

• The walls were built from the late 1800s to the early 1900s, and parts have settled as much as five feet since.
• Between that sinking and sea-level rise, water now flows over parts of the walls twice a day at normal tides.
• Despite repairs over the decades, the walls are no longer structurally sound. They threaten visitor safety and the historic setting — including the famous cherry trees.

Standing at the water's edge on a flooded walkway. NPS.

The plan

The Park Service's engineers see the job as more than repair: a chance to use technology and sustainable practices to make the landscape last, while improving access, safety and the visitor experience.

• Funding: the Great American Outdoors Act's National Parks and Public Land Legacy Restoration Fund provided $112.76 million for a design/build contract, awarded in August 2023.
• Scope: rehabilitate about 6,800 linear feet of seawall and extend its life by about 100 years. Construction was expected to start in mid-2024.
• Context: the Tidal Basin and West Potomac Park seawalls are part of nearly $500 million in planned improvements on the National Mall before the nation's 250th anniversary in 2026.

What the work includes

• New foundations: taking down and rebuilding the stone walls on pile-supported platforms, so they stop settling — and can be raised further if sea levels or storm surges keep rising.
• Higher walls: 4.75 feet within the Tidal Basin and 5.50 feet along West Potomac Park, to handle wind and waves off the Potomac River.
• Historic stone: salvaging and reusing stones from the old walls where possible.
• Better paths: repairing or replacing the walkways around the Tidal Basin and widening them from eight to twelve feet, with smoother, more accessible links to other paths.
• Drainage: regrading the ground beside the walls so water drains properly.

Trees standing in floodwater. NPS.

Sources

Based on "Revitalizing the Tidal Basin and East Potomac Park to Restore Heritage and Protect Our Future," National Park Service; a work of the United States government in the public domain. The source's title names East Potomac Park while its text describes the West Potomac Park seawalls; this page follows the text. It also lists the walkway work twice; the fuller wording is used here.