An estimated 5,000 boaters gathered Sunday on the American River for an annual party called Rage on the River, creating a “small town” of partiers and a headache for law enforcement.

The revelers floated down the Sacramento and American rivers from noon to 9 p.m. in typical Rage on the River fashion: with lots of alcohol and not a lot of clothes. The free party, which requires attendees to be on a boat instead of a raft, is promoted mostly on Facebook. At least once a year since 2010, boats have set off at Discovery Park and floated en masse throughout the afternoon.

Next weekend, law enforcement officials hope the scene on the river will be very different. From Independence Day through July 6, park entry fees will rise from $5 to $8 for single vehicles and from $10 to $13 for oversized vehicles and vehicles towing watercraft. Additionally, alcohol will be banned on the American River between Watt and Hazel Avenues throughout the weekend.

Chief park ranger John Havicon said the holiday alcohol ban is necessary because crowds present enough of a law enforcement challenge without adding drinks to the mix. Before the alcohol ban was imposed, Fourth of July river parties sometimes turned wild, with drunken rafters wrestling in the mud or clubbing each other with oars.

Sacramento Fire Department firefighter and public information officer Roberto Padilla said his agency responded to more than a dozen calls Sunday afternoon reporting heat exhaustion, dehydration and lacerations. Multiple people were transported to the hospital, Padilla said.

Also present at the Sunday event were the U.S. Coast Guard, the Sacramento County Sheriff’s Department and the Sacramento Police Department, as well as sheriff’s departments from Stanislaus, Contra Costa and San Joaquin counties.

Padilla said the event was “very chaotic” but relatively peaceful, lacking the brawls that have sometimes marred events such as Rafting Gone Wild, a river party that gained notoriety in 2012 when fights broke out among attendees, resulting in 23 arrests. The biggest problem this weekend, Padilla said, was that the crowding of boats slowed law enforcement response times.

“Some people we got a call from, we couldn’t find them,” Padilla said. “By the time we got there they were either gone or their friends took them (to the hospital).”

Rage on the River coincided with Operation Dry Water, a weekend-long national crackdown on boating under the influence. Lt. Theo Vaughan of the U.S. Coast Guard said his agency made one arrest for boating under the influence. The Sacramento Police Department arrested one person for public intoxication, according to Officer Michele Gigante.

A Stanislaus County Sheriff’s Department deputy rescued a drowning woman from the water at the confluence of the American and Sacramento rivers. Keith Rakoncza, a spokesman for the department, said the deputy did not know whether the woman was associated with Rage on the River. “The female was in an altered level of consciousness and was unable to give a statement,” Rakoncza said. “She was transported to the hospital.”

Padilla said that the majority of drownings on the river happen at the confluence of the American and Sacramento rivers. He urged boaters and other river-goers who don’t own floatation devices to visit fire stations to borrow life jackets before they head out on the water.

During the holiday weekend, the Sacramento Fire Department and the county park rangers will both increase their presence on the river. Havicon said people are generally respectful of the holiday alcohol bans.

“We have our share of drunkenness and some fights and things like on regular weekends,” Havicon said. “But I wouldn’t say it’s out of control or anything.”

Rangers are more concerned that park visitors will flout rules against fireworks. Given the dryness of the summer so far, grass fires could be a major problem.

“We don’t allow even the ‘safe and sane’ (fireworks) in the parkway,” Havicon said. “It’s a zero tolerance for us because there’s such a big chance of starting a fire out there.”