The East Bay, for all of its wonderful hiking, is not known for its waterfalls. Flowing streams, let alone tumbling cascades, are scarce amid the largely scrubby, chaparral hills that separate San Francisco Bay from California’s vast Central Valley. After springtime rains, however, there a handful of seasonal streams that come alive. One of the best-known spots is the lush, shady landscape of northeastern Mount Diablo State Park, where a moderately-difficult loop hike leads to a series of modest but beautiful waterfalls. Of course, the waterfalls largely disappear by summer, but the towering cliffs and diversity of plant life in Donner Canyon may be enough to entertain hikers year-around.
There are a few options for starting this 5.5-mile loop hike, although the choices may be narrowing as the city of Clayton begins to place restrictions on parking in the area. The ideal place to start is at the end of Rialto Drive, a residential street in Clayton that abuts the edge of Mount Diablo State Park (see directions here). But the neighbors are onto this, and non-resident parking is now barred on weekends. If it’s Monday through Friday, you’re in the clear (at least as of January 2020), but weekend hikers should look elsewhere—nearby access along Regency Drive (which is also rumored to have restrictions) or, further west, at Mitchell Canyon Staging Area ($6 park entry fee required). Note: Starting at Mitchell Canyon adds at least two miles round-trip to the loop described below. The Regency Drive Trailhead adds around ½ mile.
Assuming one starts at the Rialto Drive staging area, hikers should pass through the entry gate to enter Mount Diablo State Park, the East Bay’s largest. With the namesake peak visible ahead, the route splits just steps beyond the start. While possible to go either way, the route as described heads right, following the Falls Loop in a counterclockwise direction.
The westward route quickly climbs out of the grassy ravine and crests a low ridge before reaching a second fork within 250 yards. Stay left here, continuing as the old road drops into Donner Canyon, laced with the East Bay’s ubiquitous oak-bay woodlands. After crossing Donner Creek, the path weaves around a pair of bends, climbing to Donner Canyon Road, about 1/3 mile from the trailhead. (Note: Here the entry path from Regency Drive and Mitchell Canyon comes in from the right.) Bear left at the fork, following the dusty Donner Canyon Road for the next 1 ¼ miles.
As you proceed, the diversity of plant life increases, with lovely manzanita and toyon beginning to appear amid the oak-bay mix. Ahead, one can the high mountain tops of (from left to right) Mount Olympia (2,946’), North Peak (3,557’), Mount Diablo (3,849’), and Eagle Peak (2,369’), the titans of this scenic stretch of the Diablo Range.
Following the creek on the left, the fire road ascends gradually, passing a string of junctions at about the one-mile mark. First, a spur trail heads left to Donner Cabin, then the Donner Cabin Trail bears off to the right up ahead. Finally, stay straight on the fire road as the Hetherington Loop Trail bears left toward the creek bed. Just beyond, Donner Canyon Road begins to ascend more rapidly, the first heavy-breather of the hike. The track rises well above the creek, providing wider vistas up and down the canyon.
At 1.3 miles, pass the junction with the Tick Wood Trail on the right, then come to a junction with the Hetherington Loop Trail again on the left. Stay straight on the double-track; finally, at 1.6 miles, deviate from the main route by heading right (uphill) on Meridian Ridge Road. The westward turn is only temporary, as hikers should head south again on the Middle Trail, which begins 100 yards up the road on the left.
Now, for the first time, the path turns to single-track, a pleasant, narrow, and winding trail that weaves through dense patches of toyon, chamise, manzanita, oak, and bay. The Middle Trail provides access to Wild Oat Canyon, the heart of the falls area.
Climbing uphill through the thicket, the Middle Trail reaches a fork at 2.2 miles. Bear left on the Falls Trail, the highlight of the hike. In the shadow of Mount Diablo, this scenic track skirts the eastern flank of the canyon, then switchbacks down to the first of several stream crossings, 2.3 miles from the start. The cascades here are modest, but better waterfalls are ahead.
After crossing the first stream, the Falls Trail crests a hill topped by a gnarly juniper, then traverses a second creek. Beyond, the single-track climbs steeply to an excellent viewpoint in which one can see down-canyon to Clayton, with the Concord Hills and Suisun Bay beyond.
Rounding the next scrubby slope, the first “real” waterfall comes into view, firing off a mossy cliff and plunging into Donner Canyon below. The water flow here rarely becomes a torrent, but the sight of flowing waters is welcome nonetheless. The Falls Trail descends steeply to cross the stream above the flume, then proceeds to climb again on the other side.
After this third stream, the trail approaches a rock outcrop with a nice view back at a 15-foot falls. Then the rocky path descends again to cross a fourth creek, this one sporting a trailside cascade that is relatively modest; the stream below, however, drops more precipitously, a sight only realized after the trail pulls away from the creek on the other side.
After crossing a fifth and final stream, the route hugs a scrubby hillside and descends a set of switchbacks, offering views back at the highest and most impressive of the falls, a multi-tiered chute. The waterfalls are not easy to access, however, leading most visitors only to admire from afar.
By now the trail is situated high up on the scarred western slope of Wild Oat Canyon. The brownish Franciscan chert forms high, impressive walls, and the grade drops sharply—roughly 300 feet—off to the left. This is the end of the falls section; hikers are now heading back north toward the trailhead, although by way of a different route than the approach.
At 3.4 miles, the Falls Trail ends, merging with the wide Cardinet Oaks Road, another double-track fire road. Bear right (uphill), then turn left at the next fork on the Wasserman Trail. This scenic path meanders through very dense thickets of toyon and manzanita. Stay left at an unofficial junction at the park boundary at 3.6 miles, then descend a mild slope, partway down into Donner Canyon.
At 4.1 miles, the trail emerges into a pretty clearing and bounds down to another junction; bear right on the Donner Trail. Amid grassy, oak-studded slopes, this path heads northwest for 250 yards. Bear right on the Bruce Lee Spring Trail, which climbs again to clear a low ridge, then skirts a long ravine before ending at Clayton Oaks Road, now 4.6 miles around the loop.
Follow the fire road left as it passes two junctions (stay left) and gradually descends a beautiful ridge dotted with oaks. Eventually the strip mine of Mount Zion (1,635’) becomes visible ahead. At last, after a steady descent with open views, Clayton Oaks Road returns to the familiar starting point: the initial trailhead at Rialto Drive.
The entire loop clocks in at about 5.5 miles and, despite some occasionally steep ascents, is a moderately-strenuous circuit. Allot roughly 3-4 hours for the hike, or more if you plan to explore some of the many interlocking trails along the way.