The Spanish colonists who christened Arroyo Seco ("dry creek") evidently noted only its lower end -- a sweltering, boulder-strewn wash emptying into the Los Angeles River. It's hard to believe this same watercourse, draining the south slope of the San Gabriel Mountains some 20 miles upstream, assumes the character of a mountain brook, dancing over boulders and sliding down sheer inclines up to 50 feet in height.

If this season's torrential rains continue, that peaceful brook may be a bit too lively to explore safely for a certain period afterward -- not to mention the possibility of restricted access due to mountain highway damage and closures. For these reasons, it's a good idea to contact Angeles National Forest (626-574-1613 or www.fs.fed.us/r5/angeles/) before setting off on a trip anywhere in the San Gabriel Mountains.

Our route sampling the upper Arroyo Seco takes you by trail around the main, inaccessible falls and down to a lesser cascade in the canyon below. The starting point, the popular Switzer Picnic Area, is located off Angeles Crest Highway (State Highway 2), ten miles east of Interstate 210 at La Cañada. Be aware that by the time fair weather arrives, parking space at the picnic area will be scarce or nonexistent if you arrive after midmorning on a Saturday, Sunday, or holiday.

At the west end of the picnic area, find and follow the signed Gabrielino Trail. Make your way past outlying picnic tables and down along the alder-shaded stream. Soon, nothing but the clear-flowing stream and rustling leaves disturb the silence. Remnants of an old paved road are occasionally underfoot. In a couple of spots you ford the stream by boulder-hopping -- no problem except after heavy rain.

One mile down the canyon you come upon the foundation remnants of Switzer's Camp (now the site of a walk-in campground). Established in 1884, the camp became the San Gabriels' premier wilderness resort in the early 1900s, patronized by Hollywood celebrities as well as anyone who had the gumption to hike or ride a burro up the tortuous Arroyo Seco trail from Pasadena. The resort suffered a decline in business after the construction of Angeles Crest Highway in the 1930s and was finally razed in the late '50s.

Below Switzer's Camp the stream slides 50 feet over Switzer Falls -- but don't go that way. Instead, cross the stream and continue on the Gabrielino Trail as it edges along the canyon's right (west) wall. To the left are glimpses of the falls, a dark pit below them, and the crumbled foundation of a miniature stone chapel (a part of the old resort) that perched on a ledge above the falls. Continue 0.2 mile to a trail junction. Take the left fork (the trail to Bear Canyon) and descend to the canyon bottom. There's a severe, unfenced dropoff on the left on the way down, so watch your step.

Leave the trail there and walk along the stream bank, or rock hop through the stream itself, 0.2 mile up-canyon. You'll come upon a shallow pool, fed by a 15-foot-high cascade just below the main Switzer Falls. This is a peaceful and secluded spot for a trail-mix snack or lunch. Signs here warn against climbing farther up the canyon, and that is advice well taken.