This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Sunday, May 30, 2010

Water flowing through the spillway at Attabad

On May 29 water started flowing through the spillway at Attabad. The photo here, from Dave's Landslide blog, shows an early stage of the overtopping. The spillway is working well at these low discharges. There were some reports of landslides into the lake today, and estimates that these slides had increased the lake level by 2 feet, but I don't know if these have been verified. As of this a.m. the discharge through the spillway is estimated to be 4 cusecs (cubic meters per second).

The lake level is rising about 2.5 cm per hour, and inflow into the lake is estimated to be 71 cusecs. There is thus about a 7 cusec difference between inflow and outflow. This water is stored in the lake causing its level to rise. As it rises, the discharge through the spillway increases. One limiting case is that the spillway channel will stay at the current width, in which case the increase in discharge is directly proportional to the rate at which the lake level rises and increases the depth of the water flowing through the spillway channel.

At the other extreme, if the spillway erodes and widens, then the discharge will increase as both the area increases and the depth increases. Erosion at the bottom of the channel would increase the depth of the flow through the spillway even further. It is this later case that worries the landslide experts because the discharge could increase so rapidly under these conditions. Dave is updating his blog frequently, so tune in there rather than here!

No comments: