The proposed “Arc de Trump” in Washington is less a monument than a gaudy construction the height of a skyscraper — a travesty that, if built, would dramatically change the landscape of the nation’s capital. This is probably why President Trump is so eager to get it made as fast as he can. It would be an unavoidable monument to a presidency and a man whom many Americans would rather not honor so conspicuously, if at all. He understands that once it is there, it will be hard to for anyone to make it go away.

Change is supposed to happen slowly and carefully in Washington, and there are systems in place to make that so. When the National Park Service said last week that the arch would not only block the vista between the Lincoln Memorial and Arlington National Cemetery but would also have an impact on 35 other Washington landmarks, it was a distressing preview of the administration’s attitude toward historic preservation. The Trump administration is in the process of making it much easier to demolish historic buildings and landscapes not just in Washington but nationwide.

The Park Service’s observations were made during a Section 106 review, which has been one of our most effective historic preservation tools for the past 60 years. The name is a reference to a clause in the National Historic Preservation Act of 1966. It requires that before approval is granted for any project that uses federal funds or could affect buildings or landscapes in the National Register of Historic Places, its impact on historic places must be evaluated and the public must be consulted. The Trump administration recently proposed changes that would render this type of review process impotent. If the changes go forward, the wanton destructiveness behind the arch and the East Wing ballroom will be just the beginning.

Section 106 has had a superb record of encouraging negotiation and compromise. It does not forbid change or even demolition, but it stipulates that efforts must be made to “avoid, minimize or mitigate” any harm to historic places. The very reasonableness of the law may be exactly what has led the Trump administration to be so determined to get rid of it. In the past few years in New York, Section 106 reviews have been a part of the process that has led to the saving of the T.W.A. terminal at Kennedy International Airport as well as the conversion of a portion of city’s main post office into the Moynihan Train Hall.

The proposed changes to Section 106 were issued by the Advisory Council on Historic Preservation. This is yet another of our government’s review organizations that has been filled with Trump appointees who have no sympathy for the subject on which they are expected to pass judgment. While the proposed changes do not technically eliminate Section 106, they eviscerate it.

If this new policy is enacted, it would extend the autocratic decision-making of Trump’s Washington fiascos to historic buildings and sites anywhere in the country. It is ironic indeed for the government to commemorate the nation’s 250th birthday by embarking on what Brent Leggs, the chief executive of the National Trust for Historic Preservation, has called “an unprecedented and deliberate attack on our civic and cultural inheritance.”

The Trump administration’s revised version of Section 106 replaces “the views of the public are essential to informed Federal decision making” with a statement that says the government will have “exclusive discretion to determine the usefulness of public participation” — in effect saying that federal agencies can do as they please.

The Commission on Fine Arts, the National Park Service and the National Capital Planning Commission received tens of thousands of public comments on the ballroom and the the arch, almost all of which were negative. The commissions approved both projects anyway.

The proposed changes also state that Section 106 applies only to sites that contain actual buildings and other structures, eliminating any obligation to take public input into account in cases where natural landscapes, including the sacred lands of Native Americans, are potentially compromised. A clause requiring that Section 106 reviews begin at an early stage of design has been eliminated, making it all but impossible to suggest that a project’s site be shifted to protect something historic. The bar for defining the negative impact of a project is raised much higher. One potential new clause says that federal personnel no longer need to visit threatened sites; another clause states that any proposed mitigation of negative impact must be “technically and economically feasible.” In other words, all the government has to say is, sorry, we’ve decided it will be too expensive to run that new highway through a route that will protect a cherished natural vista. Or that it just doesn’t want to be bothered.

Over the past year, we have seen the effects of Mr. Trump’s attitudes about urban planning and historic preservation. The proposed arch will destroy the vista connecting Lincoln to the Civil War dead, a space that for more than a hundred years has been kept open as one of the capital’s most subtle acts of monumental beauty. There is also the wreck that has been made of the Reflecting Pool in front of the Lincoln Memorial and the bronze statues that have been painted in gold, using funds taken from the National Park Service budget.

And let’s not forget Mr. Trump’s insistence on painting the gray granite Eisenhower Executive Office Building a stark white to have it “match” the White House. The building is arguably the greatest work of architecture of the Second Empire style left in the United States, but when the mansard roofs and columns and terraces are all bright white it will look cheap, and worse, it will be effectively ruined. Granite is not porous, so it does not hold paint. I doubt that you can find a single painted Second Empire building in Paris, and for good reason. Does anyone think the Paris Opera would look better with a coat of white paint?

Mr. Trump’s disregard for historic preservation goes back at least as far as his reneging on a promise to donate (rather than destroy) the Art Deco bas-reliefs on the facade of Bonwit Teller, which he knocked down to build Trump Tower. He got away with that. The U.S. Court of Appeals for the District of Columbia Circuit ruled last Friday that he should have gotten congressional approval for his White House ballroom, likely leaving it up to the Supreme Court.

If the Trump administration succeeds in making its proposed changes to Section 106, it will take a wrecking ball to the historic preservation movement in the United States. And its effects will be felt across the country for generations.