Concrete dams are often made to seal off deep river valleys and create hydroelectric power. Water will build up behind the barriers, creating artificial lakes known as reservoirs. The deep water created by their construction improves fishing and boating in the area. However, the real purpose is to have the water turn giant turbines and create inexpensive electrical power.
These dams also help control floods. They are built across rivers that have a history of flooding, holding back waters in a man-made lake. The water is then released through floodgates at a regular pace so it doesn’t overflow the rivers below the dams. The idea is for the lakes behind the dams to never overflow. However, this does not always happen.
The Vaiont Dam was a structure built in the Italian Alps in northeastern Italy. A concrete barrier 873 feet above the river valley below, it kept back water from a number of small villages that dotted the waterway. In the fall of 1963, the area experienced much rainfall. The extra water eroded earth and rocks on the mountain slopes surrounding the reservoir. On October 9 of that year, part of 6,000-foot-high Mount Toc fell into the lake. A downpouring of earth, mud, rocks, and trees crashed into the water, causing tons of water to overflow the dam into the valley below.
The next morning was a scene of chaos. There were almost no buildings left standing in the village of Langarone, only piles of stones. Most of the populations of other small villages had perished.
Eventually, a study showed that the dam was situated in a poor location. If the area had been investigated beforehand, it would have been found that the area experiences frequent earth movements. Once the inquiry ended, the dam was shut down. The nearby villages have since then been rebuilt.