The Diablo Regional Trail traverses 31 miles through six East Bay open spaces—Shell Ridge, Diablo Foothills Regional Park, Mount Diablo State Park, Morgan Territory Regional Preserve, Los Vaqueros watershed, and Round Valley Regional Preserve. Running from Walnut Creek to Brentwood, this trail offers a challenging multi-day backpacking route with elevation gains totaling nearly 10,000 feet. The route crosses a patchwork of oak woodlands, chaparral-covered ridges, and grassland hills with panoramic views across the San Francisco Bay Area. Best suited for experienced backpackers comfortable with limited water sources, hot exposed terrain, and navigating through multiple land management agencies. Most backpackers complete the trail in 2-3 days.
East Bay Regional Parks Backpack Sites: Reservations required at least 2 business days in advance, phone-only at (888) 327-2757, Mon-Fri 9am-4pm. As of 2025, backpack camping costs $5 per person ages 16+, free for ages 15 and under (changing to $15 per site in 2026). Maximum 2-night stay. Reservations open in two 6-month blocks (Jan-Jun opens in fall, Jul-Dec opens in late April). Sites close seasonally November-March.
Mount Diablo State Park: Family campgrounds (Live Oak, Junction, Juniper) available via ReserveCalifornia up to 6 months advance, $30/night plus $7.99 reservation fee. No hiking permits required. Dogs prohibited on all trails and fire roads. No ground fires; BBQ grills and camp stoves only. No firewood collecting. Alcohol consumption prohibited parkwide. Maximum RV length 20 feet due to winding roads; trailers not permitted.
Dogs: Not allowed at Round Valley Regional Preserve due to endangered San Joaquin kit fox habitat. Dogs prohibited on Mount Diablo trails but permitted in campgrounds on leash.
Optimal: February-May when wildflowers bloom (poppies, lupines, globe lilies), temperatures remain moderate, and water sources flow reliably. Late winter and spring bring lush green hillsides and seasonal waterfalls along Donner Creek, best viewed day after storms.
Summer (June-September): Extremely hot with temperatures regularly exceeding 90°F, often reaching 100°F+ during heat waves. Minimal shade along exposed ridgelines. Most water sources dry up. Only recommended for very early morning starts with extensive water carrying capacity. Park may close during extreme fire danger—call ahead May 15-October 1.
Fall (October-November): Moderate temperatures return but water sources remain unreliable. Golden grasslands provide striking scenery.
Winter (December-March): Backpack camps closed. Cooler temperatures suitable for day hiking. Occasional snow possible at higher elevations.
Water is the critical planning factor. Bring minimum 1 quart per 2 hours of hiking.
Water Sources: Limited and seasonal. Morgan Territory and Round Valley backpack sites have non-potable water year-round (must filter, treat, or boil). Mount Diablo summit has potable water. Assume most natural sources dry by June and don't flow reliably again until winter rains (November-December). Plan to carry all water between camps during summer/fall.
Resupply: No on-trail resupply. Walnut Creek (north terminus) and Brentwood (southeast terminus) have full services including grocery stores. No mail drop options at trailheads. Most backpackers carry all food for the entire 2-3 day trip.
Cache Strategy: Consider staging water caches if hiking during shoulder seasons, particularly for the long exposed sections through Diablo Foothills.
Heat Exposure: Most dangerous hazard. Minimal shade, exposed ridgelines, and summer temperatures exceeding 100°F create serious risk of heat exhaustion and heat stroke. Mandatory early starts (before dawn) during warm months. Past dog fatalities from heat exhaustion have occurred—a reminder of how serious conditions become.
Rattlesnakes: Northern Pacific rattlesnakes common April-October in areas like Diablo Foothills, Morgan Territory, and Round Valley. Most active during warmer weather. Stay on trail, watch where you place hands and feet, avoid tall grass. Do not run if bitten as this spreads venom faster.
Mountain Lions: Occasionally spotted. Never approach wildlife. Travel in groups when possible.
Poison Oak: Abundant throughout the trail corridor. Three-lobed oily leaves cause rash on most people. Stay on trail to minimize contact.
Navigation: Trail crosses multiple jurisdictions and sometimes follows sidewalks, dirt roads, and singletrack. Download offline maps. Trail passes under I-680 and crosses Stone Valley Road. GPS device recommended for the connecting segments between parks.
Fire Risk: Park closures possible during extreme fire danger, particularly May 15-October 1. Always check current conditions before departure.
Northern Access (Walnut Creek): From I-680, take Ygnacio Valley Road exit east. After 3 miles, turn right on Walnut Avenue. After 2 miles, turn right on Oak Grove Road, bear right onto Castle Rock Road to staging area. Limited parking at Castle Rock.
Mitchell Canyon Trailhead (Mount Diablo north entrance): From I-680 in Walnut Creek, exit Ygnacio Valley Road. Turn right on Clayton Road, then right on Mitchell Canyon Road to end. Ranger station present. $6 parking fee. Water and toilets available.
Morgan Territory Access: From I-580, take Vasco Road north, turn left on Morgan Territory Road. Follow to staging area. Approximately 4.5 miles to backpack camp.
Round Valley (southeastern terminus): From Highway 4 in Brentwood, take Marsh Creek Road south. Follow to staging area. Backpack camp is 3.6-mile hike from Marsh Creek staging.
Nearest Airport: Oakland International (OAK), approximately 40-50 miles. San Francisco International (SFO) 50-60 miles.
Shuttles: No dedicated trailhead shuttle services operate. Most backpackers arrange car shuttle between Walnut Creek and Brentwood (approximately 25 miles by road) or hike point-to-point and use rideshare services.
Road Conditions: All trailhead access roads paved. Mount Diablo summit road has steep winding sections with blind curves—drive cautiously.
Camping Strategy: Most backpackers use the 8/14/8 mile split: Night 1 at Morgan Territory backpack camp (8 miles from Round Valley), Night 2 at Mount Diablo Live Oak or Junction campground (14 miles), finish with 8 miles to northern terminus. Reverse direction also works. Junction Campground (6 sites, first-come first-served, $30/night) offers most primitive experience in Mount Diablo.
Reservation Timing: Backpack sites open in blocks and can fill quickly for spring weekends. Call exactly when reservations open (9am on release date) for best availability. Mount Diablo car campgrounds book solid on weekends but weekday availability often good.
Water Management: Carry largest water capacity you own. 4-6 liters minimum for exposed sections during warm weather. Filter/treat water at backpack camps even though marked as available—reliability varies.
Heat Strategy: Summer attempts require alpine starts (3-4am). Hike until 10am, shelter during peak heat (10am-6pm), resume evening hiking if needed. Bring electrolyte supplements.
Wildlife: Most rattlesnake encounters occur when hikers step over logs or reach into brush. Use trekking poles to probe ahead. Wear gaiters as added protection.
Navigation Tools: Download offline maps from Save Mount Diablo's regional trail map (available through Avenza Maps app). Trail signage exists but can be inconsistent where route follows roads and sidewalks through neighborhoods.
Future Expansion: Save Mount Diablo envisions a 60-70 mile Grand Loop Trail connecting back to Black Diamond Mines Regional Preserve, though several private land gaps remain. Current trail may be extended in coming years.
Training Hikes: Consider day-hiking sections before attempting full backpack. The Las Trampas to Mount Diablo segment (5 miles, significant elevation gain) makes excellent preparation for the exposure and terrain you'll encounter.
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