WASHINGTON — With officers still reeling from the mob violence that overran Congress a year ago, the chief of the U.S. Capitol Police told lawmakers on Wednesday that his department was taking steps to address deficiencies laid bare by the attack and would implement more than 100 recommendations for improvement.

The chief, J. Thomas Manger, who took over the force in July, told the Senate Rules Committee that the Capitol Police were already addressing 90 of the agency inspector general’s 103 recommendations. 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 said in written testimony to 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.”

Mr. Bolton told the committee that only about 30 of his recommendations had been implemented. Chief Manger said another 60 were in progress, and that he had assigned an inspector to ensure that all of them are ultimately put in place.

The Capitol Police remain under tremendous strain a year after being overrun by a mob of Trump supporters who stormed the building as Congress met to count electoral votes to formalize Joseph R. Biden Jr.’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 Chuck Schumer, Democrat of New York and the majority leader, spoke at the hearing and praised the changes to the force. The top three officials in charge of security at the Capitol a year ago have all been replaced, and Congress has approved more than $70 million for upgrades to the police force.

“Today the Capitol is a whole lot safer than it was a year ago,” Mr. Schumer said.

Even so, Mr. Schumer said that the “root cause” of the mob attack on the Capitol was still a threat to the country, as former President Donald J. Trump continues to make false claims that the election was stolen from him through widespread fraud.

“What has this country come to?” Mr. Schumer asked.

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 become only tougher since the Jan. 6 attack because the agency was responding to a larger number of threats against lawmakers.

Chief Manger said the agency encountered more than 9,000 threats last year, an increase from previous years, requiring a heightened workload.

Chief Manger said the force had made key new hires and planned to ramp up recruitment efforts, including setting a goal of hiring 280 new officers each year for the next three years, as well as quickly bringing in other security workers under contract to free up sworn officers. He also outlined other improvements, including making enhancements to the way the department gathers and shares intelligence and beefing up the Civil Disturbance Unit.

“We’ve gotten new shields,” Chief Manger said. “We’ve ordered all new equipment for our Civil Disturbance officers.”

He added that the force had prepared a 25-page security plan for Thursday’s anniversary of the Jan. 6 attack.

A Department of Homeland Security intelligence analysis from Dec. 30, which was obtained by The New York Times, concluded that “threat actors will try to exploit the upcoming anniversary of the 6 January 2021 breach of the U.S. Capitol to promote or possibly commit violence, but we currently lack reporting on a specific or credible threat.”

The report said the “mostly likely threat of violence surrounding the 6 January anniversary stems from lone offenders seeking to target perceived ideological opponents, political symbols or law enforcement.”

Senator Roy Blunt of Missouri, the top Republican on the Rules Committee, highlighted legislation Congress passed last year to make it possible for the Capitol Police chief to unilaterally request the assistance of the National Guard. He said that and similar reforms were needed to better protect the police officers who were overrun during the Capitol attack.

“These officers were the true heroes of Jan. 6,” Mr. Blunt said.

Chief Manger’s testimony came a day after three police officers injured in the attack filed two separate federal lawsuits seeking to hold Mr. 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.

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.

Eileen Sullivan contributed reporting.