100-Year Flood

Eighteen years ago this month, in 1997, Yosemite Valley experienced a 100-year flood. Warm rain melted the snowpack in the high country and all that water flowed into the valley. The damage was so great to the roads and infrastructure that the valley was closed for several months. When minimal facilities were restored and I could get in, I hiked the seven-mile length of the valley, going from the east end by Half Dome to the west, surveying the damage and hoping that the places I loved have survived.

The photo above is at Happy Isles, with trees knocked down and branches piled up on the far bank of the river.

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In Tenaya Canyon, the bridge crossing Tenaya Creek above old Mirror Lake is gone, washed away like many of the other footbridges in this area. I reach the other side by stepping across boulders in the stream. The trail that went along the riverbank disappeared with the riverbank. The tranquil spot by the river that had a reflection of Half Dome overhead is gone.

In many places the water is red-orange, which indicates the presence of iron. There is an actual "Iron Spring" below the lower pool of Mirror Lake that colors the water there, but this coloring is new since the flood and starts just below where Snow Creek joins in. The pine trees in the middle section of Tenaya's landscape are dying, whether this is due to the change in the river's route, damage from the flood, the new presence of iron in the water, an infestation of insects made possible by the environmental changes, or all of the above.

Change one element in nature and the effect ripples throughout the ecosystem.

The stream’s new route flows over clean, white granite. The detritus of pine needles and branches that had accumulated over the decades, which was wonderfully soft to walk on, as well as the soil that slowly built up over the years and nurtured small meadows, were swept away by the surging water. Trees that used to line the riverbank now stand in the middle of a beach of white granite sand.

The riverbed going by Mirror Meadow has been altered from a quiet, pastoral scene to something that resembles the rugged, torn-up delta below Yosemite Falls. Furrows have been dug through its broad plain, and huge boulders line the new river banks, pushed to the side by the brute force of the water. Footbridges that managed to stay intact now have no trails leading to them or from, like London Bridge sitting in the desert in Arizona.

Below Mirror Lake, the riverbank eroded away to such an extent that the main metal footbridge across collapsed into the flood and was swept away. The flood also took shortcuts over bends in the river and swept away the Upper and Lower River Campgrounds.

At Happy Isles, where the Merced River comes down the Merced Canyon, more than 10,000 cubic feet of water per second were flowing through at the peak of the flood.

The heavy concrete bridge was destroyed. The small islands look scoured of vegetation, but the cascades still dance. Up the canyon, the metal bridge above Vernal Fall was torn off its foundation and sent tumbling down the river to wherever it is that the river collects its trinkets.

In the middle section of the valley, the broad meadows of Cook, Sentinel, and Leidig are buried under a foot of granite sand and look like a wasteland. There won’t be any wildflowers this year. The cabins below the Lodge were swept away or destroyed. The place on the bank of the Merced River where I used to sit and watch water ouzels play in the water, and where I would watch the colors of the sunset deepened and spread across the sky above the mountains, and feel the presence of nature’s great spirituality, is gone.

Other creeks that come down into the valley — Yosemite, Sentinel, and Bridalveil — as well as all the water flowing over the canyon walls added their water to the surge. In the Cathedral Rocks beach area, where I would watch mallard ducks drift by on the water, and watch climbers on El Cap through binoculars, the flood shifted the river 150 feet away, leaving a massive gravel sandbar behind. A large section of the forest eroded away on the bend, and uprooted trees still lay in the woods where they were flung.

At Valley View in the west end, where the canyon walls come together and the river leaves the valley, the rushing water compressed and flooded the forest. Everything being carried along in the water battered the trunks of the trees like bowling pins, taking out huge chunks of wood and bark. Further down the canyon, the river washed out the highway.

Looking at the meadows, I see other low areas where the river flowed perhaps a century ago. Although this flood is the largest in recorded history, it is simply another step in a long process, because looking 3000 feet above me, I see where the river used to be, before glaciers came through and carved the gentle river channel into this deep valley. But that’s a story for another time.

I will miss the beauty that I have come to love, but change is constant in nature. I look forward to the new beauty that is forming.