Wednesday, September 02, 2015

Scenes from the August 9, 2015 Vermilion Cliffs and Highway 89A Flood Event

On August 10 of this year, a large storm cell dumped significant moisture on the south facing Vermilion Cliffs near the small settlement of Cliff Dwellers. A passing motorist shot this video which shows huge rooster-tail waves running over the highway. A local news report had this to say about the large runoff event.

On August 22 I was  at the site of the flood, preparing for an 8-day river trip in Grand Canyon. I drove to the culvert area for this unnamed wash and shot pictures of the debris that was still present near the roadway.

Flaggers Wesley and Aaron work from 7 PM until 8 AM directing traffic to one lane across the damaged portion of the road (shown).

Bulldozers have been here in the ensuing 12 days since the flood, moving rocks off of the highway. They are quite large for the relatively shallow gradient of the stream here.

The dozers have cleared away much of the debris on this, the upstream side of the culvert. But the infilling inside the culvert is impressive.

Damaged fence post near boulders

Some boulders were too large to move and so they were cracked into smaller pieces

Vermilion Cliffs in the background is where the storm dumped its load. The edge of the cliff is a drainage divide and so here is the extent of the drainage area of the flood.

The downstream side of the culvert beneath US Highway 89A, four miles west of Cliff Dwellers

The main stem of the flooded wash, which is a tributary to Soap Creek Canyon. Later in the day, we ran Soap Creek Rapid and saw a few new boulders in the channel of the Colorado River, but these were from the opposite tributary, Jack Ass Canyon.

The culverts size simply could not handle the water an debris in this event and so the flood water jumped the channel. This is an undisturbed portion of the debris fan.

Another view of the waterway of the flood

Boulders casting an early morning shadow across the mud laden floodplain. It's been a great summer for monsoon rain and floods in the Southwest but perhaps just normal with respect to other seasons. What is different is that people are traveling with video cameras now and so once far away events are recorded and put on the web. On August 7, Diamond Creek flooded in Grand Canyon and you can read a boatman's account of the 10,000 cfs flood here.

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