The BBC on line today reports that thousands of people in western Nepal are fleeing before a landslide dam is overtopped which "might" lead to a large downstream flood. As of Sunday night water level behind the dam had risen to a depth of 200 m. (http://www.bbc.com/news/world-asia-32859353)
The report says that Nepal sent troops to “siphon off the water from the fast growing lake” and “authorities say large areas could be at risk of flooding if the collected waters burst.”
A large downstream flood will take place; there is no “might” about it.
The standard mitigation procedure for large landslide dams is to start digging a spillway down through the dam. Eventually, the water’s rise and the spillway meet and a large catastrophic outburst flood still takes place but with a smaller volume of water than if the spillway not been dug.
For some distance downstream all is swept away in the flood, but farther downstream the flood becomes more like a “normal” flood. i.e. bridges, roads, fields, buildings along the flood’s path are damaged but not destroyed. People are displaced and camps start to grow.
Now is the time for Tomnod to acquire the before images so that it is ready to go when the dam bursts.