Trails and the river: five areas inside fifteen minutes

The North and South St. Vrain join in the middle of town, and the state gauge just below the confluence (station SVCLYOCO, on the Colorado Division of Water Resources site) reports the flow every fifteen minutes. Read it before you plan anything on the water.

What the number means

A rule of thumb from the outfitters and the tubing regulars, not a rule. Cubic feet per second is the gauge’s unit. Children twelve and under must wear a life jacket on the river in Lyons; everyone should when it is fast.

Flow	What it means
Under 40 cfs	Low. Too shallow for tubes; fine for wading, fishing and sitting on the whitewater-park rocks. Most of September to April.
40 to 100	Mellow. Easy tubing through LaVern M. Johnson Park with a life jacket on the kids. Late summer.
100 to 300	Prime. The classic float from the Apple Valley Road bridge down through town, with the park’s drops at their best. Usually July into August.
300 to 450	Fast. Pushy water and real holes in the park; no small children. The Town flies a yellow flag. Late June and early July in a big snow year.
Over 450	Tubing closed. The Town does not allow tubing above 450 cfs and flies a red flag (double red when the river is dangerous to everyone). Kayakers and rafters only. Peak runoff, late May to mid-June.
Over 1,200	Flood watch. The Town posts advisories at this level; stay off the water and away from cut banks.

The flags at the park say it on the day: green for go, yellow for caution, red for no tubing, double red for stay out of the water. Tubing the St. Vrain has the put-ins. Anglers work both forks, best in the low, clear water of late summer and fall; Bohn Park has an accessible fishing platform, and Ralph Price Reservoir in Button Rock needs a City of Longmont permit on top of the Colorado license.

The trails

Distances and rules are from each managing agency’s own page, linked from the place. Sunrise to sunset; no camping at any of them.

• Hall Ranch, a mile west on Colorado 7. 13.6 miles. The Bitterbrush climb to the Nelson Loop is the Front Range’s classic mountain-bike ascent and a fine hike. Bikes yes, dogs no. Two lots, full by nine on summer weekends.
• Heil Valley Ranch, south off US 36. 19 miles. Picture Rock from the Lyons side links to Wild Turkey and Wapiti for a long loop. No dogs, no e-bikes; on-trail only, it is elk habitat.
• Rabbit Mountain, north-east off Colorado 66. The dry, low, early-season option with the view back to Longs Peak. Leashed dogs welcome; rattlesnakes in summer.
• Button Rock Preserve, seven miles west at the end of County Road 80. A gentle two-mile walk along the North St. Vrain to Longmont’s dam, and the Sleepy Lion loop above it. Foot only, no dogs.
• In town, the river path links the parks without crossing the highway. Flat, short, the right length for the evening. Leashed dogs; off-leash at Bohn Park.

Before you go

• Closures. The county closes trails after storms, for prescribed burns on the Nelson Loop between January and April, and for elk and raptors in season. County trail closures.
• Mud. Riding or walking a muddy trail ruts it for the season; turn back if you are leaving prints. Rabbit Mountain dries first, Hall Ranch by late spring.
• Weather. Afternoon lightning most summer days from about one o’clock; start early. Chinook winds through the canyon mouth in winter.
• Fire. Stage 1 and 2 restrictions are common from June; check the county’s current restrictions before any flame, including at the campground.
• Parking passes. The Town’s park lots use a parking pass on busy days; non-residents buy a day or season pass. The county trailheads are free.
• Emergencies. Call 911. Lyons Fire runs swiftwater rescue on the St. Vrain; the Boulder County Sheriff covers the open space.