A bulldozer crosses the swollen Boulder Creek in Boulder, Colo. Water levels have receded as intense rain abated the past two days. In Boulder County Sunday, 234 people were unaccounted for.
BOULDER, Colo. — Flood recovery efforts continued Sunday in Colorado as hundreds of residents remained unaccounted for and the death toll — as well as the number of missing — continued to rise.
Officials said at least 700 people were listed as missing in Boulder and Larimer counties after the disaster, which has washed out bridges and roads and isolated several communities.
Colorado Gov. John Hickenlooper, appearing on CNN on Sunday morning, expressed hope many of the missing are simply out of reach of communications and have “already gotten out or [are] staying with friends.”
“But,” he added, “we’re still bracing. I mean, there are many, many homes that have been destroyed.”
The tentative death toll rose to six as Larimer County law enforcement officials said a woman, 80, probably had been killed.
It’s common in disasters to have large numbers of missing people who have been displaced and briefly cut off from contact, but the numbers usually peak early and then decline as people are located.
In Colorado’s slow-motion disaster, however, the number of missing has continued to rise. As of Sunday, 234 people were unaccounted for in Boulder County, up from 218 on Saturday, said Liz Donaghey of the Boulder Office of Emergency Management. Larimer County authorities said 482 people were unaccounted for, up from 350 on Saturday.
Ms. Donaghey emphasized not everyone is missing. She is hoping the number will become clearer soon as authorities try to remove duplications of names.
Ms. Donaghey said it has been tricky to get accurate numbers of the missing because communications have been spotty or nonexistent in some areas.
“It’s not people who are necessarily missing or in danger,” said John Schulz, Larimer County’s public information officer. “Some of those people may end up missing or dead, but in most cases, it’s going to be that they just lost contact, or they’ve been evacuated and we just haven’t caught up with them yet.”
Mr. Schulz attributed the increase in missing to growing concern from relatives and friends. People assume they will hear from loved ones but become more frantic when days pass and they still have not, he said.
Just keeping track of who is out of reach and who is safe has been difficult, authorities said.
Officials in the two flood-ravaged counties have added and subtracted names as they get fresh information from relatives or rescuers. But they said communication was still spotty.
The National Guard has rescued 1,700 people from isolated areas.
Heavy rains sometimes have grounded helicopters, which have been key to reaching people where roads are impassable.
An estimated 1,500 homes have been destroyed and about 17,500 have been damaged, according to an initial estimate by the Colorado Office of Emergency Management.
In addition, 11,700 people left their homes.
As many as 1,000 people in Larimer County awaited rescue Sunday, but airlifts were grounded because of the rain, said Cmdr. Shane Del Grosso of the Type 2 Rocky Mountain Incident Management Team.
In Estes Park, some 20 miles from Lyons, hundreds of homes and cabins were empty. High water covered several low-lying streets.
At one campground in Estes Park, Jezebel the cat jumped on a sleeping Jon Johnson, batted his face, and yowled until he woke up to find the Big Thompson River spilling into the cottages he and his wife, Deyn, rented to visitors.
They ran from cottage to cottage, knocking on doors and shouting to the sleeping occupants, “Purse! Keys! Medicine! Go!”
The water rose from Ms. Johnson’s shin to her knee in less than a minute.
Everybody was safely evacuated before the river swept away three of the cottages and knocked three more on their sides.
She lamented the loss of the Whispering Pines cottages, which they have run since 1993, but praised Jezebel for her swift action. “We had no warning other than the cat,” Ms. Johnson said. “She is going to be treated like a queen for the rest of her life.”
In Glen Haven, Colo., rescuers evacuated Jerry Grove and Dorothy Scott-Grove of Cincinnati from their cabin the only way they could — clinging to a wire line strung up over raging floodwaters.
The couple abandoned their car and most of their luggage, bringing only what they could carry in a backpack.
Rescuers then carried their two golden retrievers — 85 pounds and 60 pounds — across on the zip line.
In Boulder, often called America’s fittest town, Mayor Matt Appelbaum warned people to stay out of the wide-open spaces that ring the city. “I know that people are eager to get out there again, but it’s truly unsafe.” he said. “Places that I’ve known and loved for 30 years are gone.”