There are several different types of dams:
- embankment dams built of earth or rocks (75% of all dams are of this type);
- those built of concrete, stone, or other masonry are called gravity dams;
- arch dams or buttress dams.
The selection of the site and type of dam involves a detailed assessment of such factors as geology, topography, foundation rocks, hydrology, seismic conditions and the need for construction materials. In narrow valleys with sound rocks it is preferable to build a concrete dam, while in wide valleys with less solid rocks it is preferable to build embankment dams. Earth embankment dams are the most common type as they partly use the material excavated during the foundation work.
As a result of exposure to a hazard, people, property, systems, or other elements present in the hazard zones are subject to potential losses – this is referred to as “vulnerability”. Disaster risk is the product of hazard and exposure – a source of human and economic losses.
