WASHINGTON — With officers still reeling from the mob violence that overran Congress a year ago, the chief of the U.S. Capitol Police plans to tell lawmakers on Wednesday that his department is taking steps to address deficiencies laid bare by the attack and will fully put in place more than 100 recommendations for improvement.

The chief, J. Thomas Manger, who took over the force in July, will tell the Senate Rules Committee that the Capitol Police are already addressing 90 of the agency inspector general’s 103 recommendations, according to his written testimony. They include streamlining intelligence operations and purchasing badly needed new equipment.

“We fully understand the need to restore confidence in our ability to fulfill our mission each day, no matter the circumstances,” Chief Manger plans to tell the committee, which last month heard critiques of the agency from the inspector general, Michael A. Bolton. “The men and women of the U.S. Capitol Police proved their mettle on Jan. 6. I take full responsibility for restoring confidence in the leadership of the department. We have accomplished a great deal, with more work to be done.”

The Capitol Police remain under tremendous strain a year after being overrun by a mob of Trump supporters as rioters sought to prevent Congress from certifying Joseph R. Biden’s victory in the presidential election. About 150 officers from the Capitol Police, Washington’s Metropolitan Police Department and other local agencies were injured in the violence, including more than 80 from the Capitol Police alone.

Afterward, numerous failures by the agency were made clear, even as lingering grief, trauma and fear suffused its ranks. The failures included findings that managers had not equipped the force with enough riot gear or produced an adequate plan for a potential riot, and had ignored or overlooked intelligence reports warning of attacks on lawmakers.

Senator Amy Klobuchar, Democrat of Minnesota and the chairwoman of the Rules Committee, said she believed it was important for rank-and-file officers to hear that the agency was undertaking reforms.

“It’s important for the officers who were protecting us on the front line — cuts on their faces, losing their friends and colleagues to suicide — to hear about the progress that’s been made as well and some of the improvements in morale,” Ms. Klobuchar said in an interview. “In some cases, the insurrectionists had better gear than they did.”

Ms. Klobuchar noted that Capitol Police officers’ jobs had gotten only tougher since Jan. 6 because the agency was responding to increased threats against lawmakers. At a news conference on Tuesday, Chief Manger said the agency encountered 9,600 threats last year, requiring a heightened workload.

He said the force had made key new hires and planned to ramp up recruitment efforts. In his submitted testimony, he outlined other planned improvements, including enhancements to the way the department gathers and shares intelligence and beefing up the Civil Disturbance Unit.

Chief Manger’s testimony comes a day after three police officers injured in the attack filed two separate federal lawsuits seeking to hold former President Donald J. Trump accountable for the violence.

One suit was filed by Officer Marcus Moore, a 10-year veteran of the Capitol Police who is invoking the Ku Klux Klan Act of 1871 to seek to hold Mr. Trump responsible for his “central role in inciting the Jan. 6 insurrection and the resulting attack on the law enforcement officers defending the peaceful transition of power.”

In his suit, Officer Moore recalled rioters pinning him against a wall, punching him repeatedly, spraying bear spray in his face, calling him racial slurs and threatening to take his weapon and kill him with it. “We are not going to die like this!” he recalled saying.

The other was filed by two Washington police officers, Bobby Tabron and DeDivine K. Carter, who were attacked relentlessly outside the Capitol and in a tunnel on the West Front of the building that officers now refer to as the Tunnel of Death. They were struck with fists, flagpoles and projectiles, and sprayed with chemicals, according to their suit. Officers Tabron and Carter were uncertain whether they would make it home alive, according to the suit, as they battled for their lives and to defend the Capitol.

Their suit also cites the Ku Klux Klan Act and asserts that Mr. Trump — who told supporters to “fight much harder” and “show strength” at a rally on Jan. 6 while urging them to head to the Capitol — violated laws against inciting a riot, disorderly conduct, civil conspiracy and aiding and abetting assault and battery.

“Our clients suffered physical and psychological wounds as the result of insurrectionists incited by the former president to disrupt the peaceful transfer of power,” said Patrick Malone, a lawyer for all three officers.

The suits bring to at least six the number filed against Mr. Trump by people who were at the Capitol during the attack.

Lawyers for the former president have argued that Mr. Trump should not be held liable for the actions of the mob, citing both his right to free speech and a claim of presidential immunity.

“To attempt to hold a political leader vicariously liable for the actions of others as a result of constitutionally protected political speech would contradict the Supreme Court’s well-established First Amendment precedent,” Mr. Trump’s lawyer, Jesse R. Binnall,wrote in response to one suit. “Even if the speech in question was not cloaked with the highest presumption of legal protection, plaintiffs’ claims are precluded by absolute presidential immunity.”

Oral arguments are scheduled for Jan. 10 in suits filed against Mr. Trump by Representative Eric Swalwell, Democrat of California; Representative Bennie Thompson, Democrat of Mississippi; and Officers James Blassingame and Sidney Hemby of the Capitol Police.