Sgt. Steve Perez, 60, had worked 34 years with the department, Acevedo said at a news conference.
Acevedo praised Perez's dedication to the job. The officer's wife had urged her husband not to go to work that day because conditions were too dangerous, as did his father-in-law, Acevedo said.
"And his response was, 'We've got work to do,'" the chief said, choking back tears.
Perez, who worked in the traffic enforcement division, left home around 4 a.m. Sunday to drive to his duty station downtown but "could not find a path" because flooding caused by tropical storm Harvey had made many roads impassable, Acevedo said at a news conference.
Investigators determined Perez tried for two and a half hours to find a way, before calling a supervisor and saying he'd report to his secondary duty station, the chief said.
On Monday morning, Perez's supervisors noticed he did not attend roll call and, after contacting his family, launched a search, Acevedo said.
The search team determined his probable path and narrowed down his last location to the Hardy Toll Road in Houston, Acevedo said. The dive team was called, but the operation was put on hold because the rescue attempt would have been too treacherous Monday night.
"We made a decision to leave officers there waiting until the morning, because as much as we wanted to recover him last night, we could not put more officers at risk for what we knew in our hearts was going to be a recovery mission," the chief said.
The dive team found Perez's body around 8 a.m. Tuesday, Acevedo said. The officer drove into floodwater and died "in a drowning type event," the chief said.
"Steve was one of the sweetest people I've met in this department," Acevedo said. "I've only been here nine months and we've got, you know, 6,500 employees and I knew who Steve Perez was, because he was a sweet, gentle public servant."
Acevedo said the officer's death is hitting the department hard, especially because so many officers are stressed from working non-stop while floodwater rises.
The mayor applauded the dedication of the police force.
"Every single day we ask our men and women in blue to show up, to come to work when conditions are good and even when conditions are very challenging," said Houston Mayor Sylvester Turner. "And every day, we ask them to get on our roads and to come to work and to strive to make this city a much better place in which to live."
"Today, I will simply say that our hearts are saddened. We grieve with this family. We extend to them our prayers from the entire Houston community, and, quite frankly, even beyond," Turner said. "He was seeking to serve this city and all those who would come in to our city."