The agency is proposing a massive project to restore 6,800 feet of seawall around the Tidal Basin and in West Potomac Park, and redevelop the shoreline.
A $5.7 million contract has been awarded to begin planning.
The basin, which dates back more than a century, is one of the focal points of the National Cherry Blossom Festival, when it is crowded with people who gather to view and photograph the cherry blossoms.
The basin is also the site of the Martin Luther King Jr. Memorial, the Thomas Jefferson Memorial, and the Franklin Delano Roosevelt Memorial, which attract visitors year-round.
But parts of the levee have been sinking for years, and the structure and its walkway are often submerged by tidal flooding. In some places, the wall has sunk as much as four feet since it was rebuilt in the 1930s and 1940s, the Park Service said.
Ten years ago, the agency spent more than $12 million to repair the seawall in front of the Jefferson Memorial, where it was slipping and sinking in the mud.
This section was believed to have failed because it was built on a foundation of wooden piles that were not long enough to reach bedrock. The old foundation was replaced by piles and concrete caissons resting on rock.
A contract to design and execute the project will be awarded next year or early 2024, the Park Service said.