A dam is a man made barrier usually built across a river to hold back water and forming a lake, or reservoir, behind it. It can be constructed from concrete or natural materials like earth and rock.
Cross-section through an embankment dam
A cross-section (or slice) through an embankment dam shows that it is shaped like a bank, or hill. Most embankment dams have a central section, called the core
, made from an impermeable
material to stop water passing through the dam. Clayey soils, concrete
or asphaltic concrete
can be used for the core.
Reinforced concrete cover on upstream face of Quoich Dam
A gravity dam is made from concrete
, or sometimes both. It is called a gravity dam because gravity holds it down to the ground stopping the water in the reservoir
pushing it over.
Cross-section through gravity dam
A cross-section (or slice) through a gravity dam will usually look roughly triangular.
Gravity dams are suited to sites with either wide or narrow valleys, but they do need to be built on sound rock.There are more than 250 gravity dams in Britain. Masonry was used in many early dams, as far back as the 17th Century. However, concrete became more common from about 1900.