Model this Breaching Mechanism!

Chinese Landslide Dam Failure Flood in Action

This photo pair is interesting. Amazing how close the community is to the landslide dam...it so easily could have been partly buried by the landslide...but in that case, maybe the valley could not have been dammed so easily. Moot, obviously.

Landslide Dam Failure in China

The significance of these photos to the average Yeehow is quite clear. The principal landslide dam following the recent major earthquake in China has failed. These photos show the breach and the incredibly cool draw-down tongue. For some cogent discussion about this event, check out the blog of Dr. David Petley at which I found the bottom two images and a lot of commentary: http://daveslandslideblog.blogspot.com/

Damming Ruminations by Brother Spud

Hi Folks,
Here are the figures from my thesis that relate to the last post I made on friday night. I hope they help you visualize some of what I described.

-Spud


Figure 2. Exposure of the Saddle Butte lava near Read-it-and-Weep rapid (river kilometer 34.25). Exposure shows foreset beds of hyaloclastite and lava pillows, the passage zone, and subaerial lava. The foreset beds of pillow lavas and hyaloclastite dip down to the right, indicating that the lava advanced from left to right into a body of standing water. Much of the hyaloclastite has altered to orange-colored palagonite. The passage zone marks the elevation of the water surface. Above the passage zone, subaerial lava was emplaced. Exposure is ~60 m thick.

Figure 15. Aerial photograph of river kilometers 37.5–39.5 showing presumed initial location of West Crater lava dam. The Owyhee River flows to the north in this image. The red dashed ellipse marks the location of a possible spillway in the West Crater dam and/or the initial point of breaching. The asterisk denotes the location of the sediment lens depicted in Figure 16. Ryegrass Creek defines the western edge of the Saddle Butte lava flow. The West Crater lava flow entered the Owyhee Canyon by flowing down the Bogus Creek canyon. Enough lava was supplied to the Owyhee Canyon that the dam was able to grow upstream towards Ryegrass Hot Spring.

Figure 16. Photograph of outcrop relations at river kilometer 39.25. The Saddle Butte lava appears to underlie the sediment lens in the center of the photograph. The head of the West Crater lava dam overlies the sediment lens and the Saddle Butte lava. Foreset beds of pillow lavas and hyaloclastite dip down to the right in this image. Several different passage zones (indicated by PZ) indicate the lake level rose during construction of the dam. The location of the paleovalley wall discussed in Figure 15 is indicated by a dashed ellipse. The lens of sediment interpreted to be paleo-Ryegrass Creek is visible in the center of the photograph.