Thunder Creek Trail

Thunder Creek Trail is an easy out-and-back from Colonial Creek Campground to the first wooden bridge over the creek, through old-growth forest. The mapped trail line is 1.32 miles one way, and the detailed route description puts the bridge at about 1.5 miles. A separate day-hike listing gives 4 miles round trip. I’d use about 3 miles for the mapped walk and leave room for extra campground walking or time at the creek. Allow roughly 1.5 to 2 hours; the published elevation gain is about 105 feet.

Park in the lot above the boat ramp and follow the campground signs to the amphitheater, where the trail begins. The first half-mile follows Thunder Arm of Diablo Lake. Then the dirt path winds through large cedar and fir with occasional glimpses of the creek. The wooden bridge is the natural turnaround. Cross it for the view of the water and nearby gravel bars; the bridge itself is the best place to frame the blue creek with the forest around it.

Fine rock dust ground by glaciers in the creek’s headwaters stays suspended in the water and gives it its cloudy turquoise color. The trail lets you see that color change as the creek narrows and runs under the bridge.

Look for very large cedar and fir, and woodland flowers when they’re in season. Owls, woodpeckers, and osprey are among the birds noted along the creek; listen as well as look. Prospectors and trappers opened the route, then mining developers and the Forest Service made major improvements in the early 1900s. Old blazes and cut stumps still mark parts of that history.

The trail continues beyond the bridge. About a quarter-mile farther is the Fourth of July Trail junction, where a steep climb heads toward the pass. That’s a separate, harder outing. The lower bridge walk is in the Ross Lake National Recreation Area, where leashed pets are allowed; pets are prohibited farther south after the route enters the national park. Overnight trips farther up the corridor require a limited backcountry permit.