SALT LAKE CITY — A memorial service has been planned later this month for the one-year anniversary of fatal flash floods that ravaged a polygamous community on the Utah-Arizona border, killing at least a dozen people.

An evening service is scheduled Sept. 14 in Colorado City’s Cottonwood Park, Terrill Musser said. Musser, a member of a community group planning the event, said people will talk about their experiences during the flooding then walk to a nearby bridge for a candlelight vigil, the Spectrum newspaper in St. George reported. ( ).

The event is meant to honor the victims and thank first responders and others who helped in the rescue efforts in September 2015.

“I don’t think we ever really thanked them properly,” Musser said.

The same storm killed seven hikers who drowned in a narrow canyon in Zion National Park and a man from nearby Hurricane, Utah — making it one of the deadliest weather events in Utah history.

The sister towns of Hildale, Utah, and Colorado City, Arizona, were hit the hardest.

Three women and 13 children were returning from a park when they stopped at a flooded crossing on a gravel road north of the towns to watch the gushing waters. They were inside a van and SUV when a wall of brown water surged out of a canyon above and carried away the vehicles. The cars were carried downstream and plunged into a flooded-out embankment, with one vehicle smashed beyond recognition.

The bodies of 12 people were found amid mud and debris miles away. Three boys survived. The body of one boy, 6-year-old Tyson Black, who is presumed dead, has never been found.

Washington County Sheriff’s Deputy Darrell Cashin said they still do periodic searches, including after some recent storms.

“We have just had no luck,” Cashin said.

The state of Utah funneled about $1.5 million in emergency funds to the community last October to build a 100-foot bridge across a flooded wash and construct culverts and canals near where the victims’ vehicles were sitting when the floodwaters engulfed them and carried them several hundred yards downstream.

The community was recently given an additional $670,000 in state funds to build several ponds to collect rain runoff to help prevent another tragedy. The funds came from Utah’s Permanent Community Impact Fund Board, which uses royalties from mineral and energy development to give communities grants and loans.

Hildale also plans to use about $1 million in federal money for a fourth retention pond.

Hildale Mayor Philip Barlow said recently he hopes the ponds will keep water from building up and sweeping over roads like it did during the deadly storm.

Resident Dowayne “Dee” Barlow told the Spectrum that he hopes the anniversary brings the community together again for healing, forgiveness and love.

“I think the flood changed mindsets significantly,” he said. “I think it brought about the realization that we have to stand up for our families or they can get swept away by the flood of ideologies here.”

Information from: The Spectrum,