Thursday, July 25, 2013

Around Ebbett's Pass: waterfalls and flash floods during summer

Ebbett's Pass or Ebbetts Pass is part of a scenic landscape in Alpine County, California. The pass is surrounded by historical landmarks and sites, ancient volcanic peaks and rock formations, alpine lakes and canyons. The Carson-Iceberg Wilderness is located south of the pass and can be accessed via Noble Lake by hiking from the Ebbett's Pass Trailhead southward on the Pacific Crest Trail (PCT).

By scanning the ancient volcanic landscape, you may imagine how lava was flowing here in the past. These days, water is flowing down the slopes. The top pictures shows a small waterfalls trickling down (prior to a later thunderstorm) some granite rocks and cliffs. At other locations streams of snowmelt water flow downhill between eroded volcanic debris. You will have to cross several streams along the trail on your way to the upper Noble Canyon and Noble Lake. During summer and fall, these runoffs are typically slow-flowing and quiet—sometimes dried-out. But they may quickly turn into stronger ones during a summer rainfall, hailstorm or severe thunderstorm.

A weather pattern of common afternoon thunderstorms is known for this area. On July 21 of this year, we experienced such a thunderstorm with dark clouds gathering and colliding above us—almost out of nowhere, while hiking on the east-facing slopes of the Pacific Crest. The result was some rain followed by a long-lasting pour-down of pea-sized hailstones. The most striking phenomenon was how soon water—not much of which is getting adsorbed by the small amount of soil in this landscape—started flooding down from all sides. The picture above shows gray-brown water rapidly flowing over the PCT, which literally disappeared at those sections. Returning to the Ebbett's Pass Trailhead by crossing over several of those muddy streams was more risky than we thought it would be. What looked like a good stepping stone in the flowing water or mud, often turned out be a sliding rock—fortunately, still moving slow enough to jump off onto less slippery ground. Yet, the danger of encountering a heavier mudflow or a small landslide between the trees and over the forest openings became real.

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