GLENWOOD SPRINGS — Even in land-locked Colorado, Memorial Day served as a day at the beach for folks across the state.

High water in rivers statewide brought out the adventurous and encouraged others to take a more cautious approach and enjoy the views from dry land as the potential hazards of swift and surging currents began to reveal themselves at the start of what is expected to be a banner year for snowmelt runoff.

"It's a blessing in that our overall season ends up being really, really good," said Antony McCoy, head boatman and operations manager for Vail-based Timberline Tours whitewater rafting company. "But during the early season in a year like this, we often have to reroute and run trips differently than normal in the name of safety. Out decisions are always based on safety first and fun second, and we make those decisions day by day."

With warm temperatures and weekend precipitation boosting flows, Timberline Tours and other established commercial rafting companies were forced to make reroute Memorial Day trips away from the raucous Dowd Chute section of the Eagle River between Minturn and EagleVail. The company institutes a cutoff for commercial trips through the Class IV-plus run when the river broaches 4½ feet on the gauge installed atop Dowd Chute, launching just below the most severe whitewater rapids instead.

"That's a fun level for expert kayakers, but it gets tricky in a raft," McCoy said. "And with water this high, most clients don't really notice the difference. They still love it."

Ironically, it's just about the time that many commercial rafting companies begin to take more extreme precautions when many of the most daring decide that conditions are optimal.

A few miles below the Eagle River's confluence with the Colorado River, the state's growing cadre of river surfers arrived en masse at the increasingly renowned Glenwood Springs Whitewater Park on Monday. There they were greeted by river flows unseen on the Colorado since the high-water year of 2011, measuring in the neighborhood of 16,000 cubic feet per second below the confluence with the Roaring Fork River.

"I drive up here from Boulder just about every weekend this time of year," said Ben Smith, a stand-up paddle (SUP) surfer of two years who had never ridden the river at flows above 5,000 cfs before this spring. "This season, I'm going to surf it as much as I can, and every weekend is like a new experience for me. It's a different wave each time. Better and better."

Surfers on Monday's unofficial launch of summer were lined up as many as 10 deep on both sides of the Colorado River at West Glenwood, some with paddles and others with traditional surfboards diving headlong into the raging currents before popping to their feet for rides lasting several minutes. They alternated with — and largely outnumbered — skilled whitewater kayakers performing tricks in the frothy whitewater as spectators on the banks took in the show. One photographer launched a drone above the surfers to capture the action on video.

"This wave is by far my favorite," Smith added. "A lot of kayak play holes have a big foam pile that's designed to hold the kayaks in the play spot, whereas this wave is so steep that it's gravity that's pulling you down the face of it, which is what an ocean wave does. Plus it's so clean. You can make these nice big turns on a clean, green wave. It's the closest thing to ocean surfing I think that you are going to get in Colorado."

In a state renowned for its paddlesports offerings and participation, it comes as no surprise that Smith and several others have adapted a paddle to the surfing equation. Credit for SUP's origin goes back to Honolulu, where it was known as "beach boy" surfing by the Hawaiians who used paddles while standing to photograph tourists taking surfing lessons more than 50 years ago. The sport's recent resurgence on the ocean has rapidly crept inland during the past decade, where it has established a home on and around the beaches of Colorado.