The Tidal Basin gets a lot of attention for a certain tree species that has showy blossoms this time of year. But few of the thousands of tourists who descend on the Tidal Basin each spring appreciate it for the marvel of 19th century engineering that it is.

The basin, built between 1882 and 1909 out of the of the silted-up mudflats of the Potomac River, was designed to harness the power of the river’s tides to refill itself with fresh water on a daily basis. It happens automatically, without the intervention of man or machine, as the tides ebb and flow, pushing giant wooden gates open and closed.

Now, the tidal gates are about to get an upgrade from the U.S. Army Corps of Engineers. The Corps is getting $400,000 for engineering and design of either new gates or to restore the old ones. The funding comes from the recently passed federal infrastructure law.

The Tidal Basin has inlet gates, located on the Potomac River just north of the 14th St. Bridge, as well as outlet gates, near Maine Ave. where the basin flows into Washington Channel. When the tide is rising, the water pushes the inlet gates open and the outlet gates closed. When the tide is falling, the water pushes the inlet gates closed and the outlet gates open. This flushing action was intended to help flush out Washington Channel, preventing sediment from building up there and inhibiting boat traffic.

In addition to the automatic, swinging tidal gates, there are also flood gates that roll up and down like garage doors. These “curtain gates” were designed to be mechanically raised and lowered with the help of heavy iron counter-weights (like old window sashes). This set of gates was intended to be closed during flooding, to prevent silt and debris from rushing into the basin.

While the swinging tidal gates are still working, the curtain gates are no longer functional.

To replace or restore the gates, the Army Corps will first need to conduct a full inspection of them, likely sending divers into the murky waters to document the gates’ underwater condition. They may also have to remove large amounts of debris that have built up outside them over the years.

The Army Corps is also getting $6.25 million for work on the levee system on the National Mall that prevents flooding downtown. This includes constructing a new levee closure across 23rd St. at Constitution Ave., as well as raising the height of the 17th St. levee closure.

The Tidal Basin was constructed by the Army Corps, along with the East Potomac Park and parts of the National Mall, by filling in wetlands with dredged material. The basin and parklands along the river are threatened by climate change and rising sea levels, frequently flooding throughout the year. The Potomac has already risen 11 inches over the past 100 years, and is expected to rise at an accelerated rate in coming decades.