introduction to mass wasting causes of mass wasting prevention of mass wasting types of mass wasting
FALLS (rock fall and rock avalanche)
FLOWS (rock avalanche, debris flow, earth flow, and creep)
Vaiont Dam Disaster
This is a
photograph of the Vaiont River Valley in northern Italy, taken by Ed Bromhead.
In 1963, a major rock slide resulted in the deaths of approximately 2600
people. The slide block, labeled on the photograph, moved suddenly
into the newly filled Vaiont Reservoir, flushing lake water up and over the
dam. The wall of water was over 200 feet high as it swept into
nearby villages, wiping out everything in its path.
The rock slide and the ensuing flood could have been readily forseen if better geological consulting had been done before construction of the dam and reservoir. The sedimentary rocks of the Vaoint River Valley include layers of shale, a clay-rich rock. And, the rocks comprising Mt. Toc (pictured), tilt steeply toward the reservoir. After the dam was finished in 1960, filling of the reservoir introduced groundwater into the shale layers, causing them to swell and become slippery. At first, the mountainside began slowly creeping down slope at a rate of half an inch per week. As filling continued and more groundwater seeped into the mountain, the rate of slippage increased to eight inches per day, and ultimately to 30 inches per day just before the 1963 disaster.