Crowds are minimal. Water is available at the trailhead.
To Reach the Trailhead Take the Ygnacio Valley Rd. off-ramp from Hwy. 680 in Walnut Creek and proceed 9 miles east on Ygnacio Valley Rd. to Clayton Rd. Turn right and in 1 mile turn right again on Mitchell Canyon Rd., proceeding 2 miles to the lot at the road’s end. There is a day-use fee of $10 per vehicle.
Description From the parking lot (0.0/640'), begin by the fire gate and information sign and start up Mitchell Canyon Rd., bearing left onto Mitchell Rock Trail at the immediate junction. Stay on the wide trail as you pass two junctions for Bruce Lee Trail before turning right on singletrack Mitchell Rock Trail (just past the second Bruce Lee intersection). In season, abundant wildflowers liven the ground here and throughout the hike—look for California poppies, yarrow, paintbrush, lupine, irises, orange bush monkeyflower, yerba santa, blue dicks, Ithuriel’s spear, and the endemic Mount Diablo fairy lantern.
As you climb upward into thick forest, note the increasing number of pine trees. Two pines are found in this area, both producing massive cones with sharp hooks on the scales. Gray pine is the more common, abounding throughout California’s foothills and easily identified by its wispy character. Its upper half, often drooping slightly to one side, tends to fork into a multitude of small branches with no clear center trunk. Its long grayish needles come in groups of three and give the tree its name. Coulter pine, on the other hand, is straight, stout, and considerably less common than gray pine, occurring only in the Coast Ranges from Mount Diablo south. They are at the northernmost limit of their range here and can be identified by their single trunk, long stiff needles (also in groups of three), stouter appearance, and gargantuan cones. Coulter pine cones are the largest known, giant loaves 12–14 inches long that easily weigh several pounds.
As you climb steadily, your views north of the creeping edge of suburbia continue to improve until you reach an open rock platform (0.6/1,080'). Directly across Mitchell Canyon, noisy Lone Star Quarry digs up diabase for use in roadbeds and foundations. Continuing up the trail, you ascend to a small saddle below Twin Peaks. As you traverse below Twin Peaks to attain the ridge, the Sacramento River Delta appears to the north and the broad expanse of the Great Central Valley peeks out east over the hills. An eagle eye can discern the confluence of the San Joaquin and Sacramento Rivers. Once on the ridgeline, views open up of the Mount Diablo massif—both North Peak (3,557') and the summit (3,849') are visible. From Twin Peaks (1.5/1,733'), Eagle Peak is clearly seen up the ridge.
Descending briefly, the trail passes a junction for Eagle Peak Trail (your return route) and then makes a steep, brushy, view-rich climb up the ridgeline to just below the summit, where a series of final switchbacks brings you to the top (2.3/2,369'). Bear right on Eagle Peak Trail on your downhill return from the summit to take a much steeper and more direct route to the bottom than Mitchell Rock Trail. Dropping above Back Creek canyon, the trail cuts sharply back before passing over a scree gully below Twin Peaks. As you continue to descend, an increase in pines and poison oak marks the approaching junction with the Coulter Pine Trail (3.4/780'). Bear left and enjoy the gentle ramble through flowers and oaks and rippling grass that returns you to the Mitchell Rock Trail and your trailhead.
Nearest Visitor Center Mitchell Canyon Ranger Station, near the end of Mitchell Canyon Rd., is open weekends 8 a.m.–4 p.m. during spring and summer, and 9 a.m.–3 p.m. in fall and winter. For general information, call 925-837-2525.
Nearest Campgrounds There are no park campgrounds accessible from the north side of Mount Diablo State Park, but 3 year-round campgrounds are accessible from the south side: Juniper Campground, the largest, is along Summit Rd.; small Junction Campground is by park headquarters; and Live Oak Campground can be found on Mount Diablo Scenic Rd./South Gate Rd. (all campgrounds $30). Reservations are recommended for weekends; visit reserveamerica.com or call 800-444-7275.
Additional Information mdia.org, savemountdiablo.org, and www.parks.ca.gov
HIKE 16 Cosumnes River
Highlights Valley oak woodlands and wildlife
Distance 3.0 miles round-trip
Total Elevation Gain/Loss 10'/10'
Hiking Time 1–2 hours
Recommended Map USGS 7.5-min. Bruceville
Best Times October–April
Agency Cosumnes River Preserve
Difficulty
COME EXPERIENCE California’s great Central Valley as it used to be, a world of magnificent valley oaks flush with wetlands, wildlife, and wildflowers. The Cosumnes River flows through the preserve, the only remaining undammed river in the Central Valley. Migratory sandhill cranes flock here from November through February, for many the highlight of a spectacular birding destination year-round.
The Hike loops on easy level paths through the preserve, visiting ponds, meadows, riparian woodlands, and the banks of the Cosumnes River. The described hike meanders through much of the preserve, though it is also possible to make a shorter loop if desired. Open year-round, the preserve is best visited during the cooler months as summer temperatures can be scorchingly intense. Note that sections of trail can be flooded in winter following heavy rains.
To Reach the Trailhead Take I-5 to the Twin Cities Exit in Galt, turn east, and proceed 1.1 miles to Franklin Blvd. Turn right on Franklin Blvd. and continue 1.9 miles to reach the preserve entrance and main parking area.
Description The hike begins from the visitor center on the paved River Walk (0.0/20') and quickly proceeds into shady woods of young valley oak. Also present are prime examples of the many massive poison oak shrubs that grow throughout the preserve.
Recognize valley oak by its distinctive deeply lobed and rounded leaves. Once common throughout the central Valley, its population has been dramatically reduced by agricultural development. Today only a handful of locations still harbor portions of undisturbed valley oak habitat—this preserve is one of the best remaining examples.
You next cross a bridge over the Willow Slough floodplain, where a sign highlights the remarkable fact that here, more than 60 miles from San Francisco Bay, the elevation is a mere five feet above sea level and that tides cause the water here to rise and fall as much as five feet each day.
The path reaches a junction by wetlands (0.1/10'), where you turn right. The path winds by the edge of a pond and alongside wetlands thick with willow and oaks. It then travels atop a berm with wetlands on both sides, where you can see abundant “balls” hanging from many oak trees. These are striking examples of galls, which are created when insects lay their eggs on oak trees. This stimulates the tree to produce distinctive structures in response, which protect the young insects as they hatch. Hundreds of different types of gall-producing insects exist, each of which generates a different structure. A careful eye will find other varieties on leaves and branches throughout the preserve.
Urnlike barrels appear beside the trail as you continue. Part of the preserve’s restoration efforts, they hold water to irrigate the plants along the berm. Turn left at the next junction (0.5/10'), where a short dead-end spur continues straight to a partial view of the Middle Slough.
At the next junction (0.7/10'), turn right to briefly parallel the railroad tracks on a dirt road, then go right again at the next junction (0.8/10') to remain on Nature Trail as it heads down toward the river. A grassy path now leads to a T-junction, where you turn left and attain a levee alongside a stand of riparian valley oaks. The large birdhouses you see, for wood ducks, mimic the large tree cavities the birds prefer.
The route curves left to return by the