(Dhalaamacune,  Oct  22,  2009 Ceegaag Online)

The reservoir was surrounded by an impermeable layer of soil; one that water cannot escape. The activity documented at the time the water level dissipated, probably disturbed a blocked outlet to the body of water. This has allowed for the flow of water to take place and the reservoir to drain.

Meanwhile, the flow of water created by draining damaged the impermeable layer that once sustained the reservoir. Once damaged, water seeped into and saturated the adjacent soil. This increase in the second layers water content decreases the strength of the soil and failure occurs (due to the application of effective stresses). The soil will continue to fall into the hole until the remaining flow of water seizes or the slope becomes 45 – 60 degrees.

Figure 1: Reservoir before flow of water.

Figure 2: Reservoir during flow of water.

Rex Radloff  

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