Monday, April 9, 2018

The Difference a Day Makes: Yosemite 24 hours after the Deluge

Photographed by Garry Hayes


First off, thank you to the National Park Service for making the flood photographs available on their Facebook page. And second of all, kudos to the National Park Service for weathering the flood and opening the park again so soon afterwards.

I was in Yosemite Valley today, leading my students on a postponed field studies class in the park. Why did we postpone the trip? Well, mainly it supposed to take place on Saturday, but it turned out that the valley was in the midst of dealing with one of the larger floods it has experienced, about the fourth or fifth largest in 30 years or so. Plus, they closed and evacuated the park in advance of the storm. They only opened up again at noon today, and we were at the park boundary at precisely 12:11 PM.

The storm was epic. It was an atmospheric river storm, a "Pineapple Express" that brought many inches of very warm rain to a snowpack that had fallen only in the last few weeks. Rain was falling at elevations as high as 10,000 feet. The runoff gathered quickly into the streams and rivers, and the Merced went from around 1,000 cubic feet per second to more than 12,000 cfs. Water level at the Pohono Bridge gaging station rose from 5 feet to almost 14 feet. For reference, official flood stage begins at 10 feet, and at 12 feet the main valley roads are covered with water. It could have been a disaster if the valley had been full of tourists.
Source: https://www.cnrfc.noaa.gov/graphicalRVF.php?id=POHC1

But instead, the weather cleared, and the park service maintenance people worked quickly to clear debris from the roads and bridges. It couldn't have been easy, and there were lots of anxious tourists hoping their vacations wouldn't be totally ruined. They came through, and now you can compare the difference 24 hours can make.
Source: National Park Service

24 hours ago, clouds obscured the cliffs, and one could barely making out the raging torrents of Upper Yosemite Falls. This afternoon, there was not a cloud in the sky, and while slightly diminished in volume, the falls were as powerful as they will probably be for the rest of the year.
Photograph by Garry Hayes

The river rose to cover Cook's Meadow, but as the sign shows, nowhere near the level of 1997's even more epic flood. The discharge was twice as high then as it was yesterday, at 24,600 cubic feet per second.
Source: National Park Service
Today the sun shone brightly on a still-flooded meadow, but the water had receded enough that we could follow the boardwalk across the open space.
Photograph by Garry Hayes

I may be posting more pictures soon, but I had to lead off with these since by chance I was standing close to where the photographer was standing yesterday.