ABSTRACT
A dam is required to impound the water, and its design and construction must be capable of preventing the uncontrollable leakage of reservoir water around and beneath its structure. The volume of a reservoir is reduced by deposition within it of river sediment and landslide debris. Sediment will accumulate as deltas at the margins of a reservoir, where rivers discharge into the lake. The effect of a rise in reservoir level on the stability of a slope has been likened to the behaviour, on submergence, of a mechanism composed of two blocks linked by a freely pivoting rigid beam. Geological surveys of reservoir slope stability are commissioned if it is feared that landslides into a reservoir may either significantly reduce its volume available for storage or produce a tidal wave that may over-top the dam and cause flooding downstream. Reservoirs in mountainous terrain are vulnerable to landslides activated by earthquakes.
