Topography
A narrow U-shaped valley flowing between high rocky walls would suggest a concrete dam.
A low-rolling plane country would suggest an earth fill dam.
A narrow V-shaped valley indicates the choice of an arch dam.
Geology and Foundation Conditions
The foundation strata should be strong enough to carry the weight of dam. Hence the dam site must be surveyed by geologists so as to detect the thickness of foundation strata, presence of faults, fissured material etc.The various types of foundations generally encountered are :-
Solid-rock foundation
Similar like granite, gnesis etc. Almost every type of dam can be built as it is strong enough to withstand the self weight of the dam and external forces acting on the dam.
Gravel foundation
This type of foundation is suitable for earth and rock fill dams. For this foundation, low concrete gravity dams upto height of 15 meter may also be suggested.
Silt and fine sand foundation
This type of foundation suggests the adoption of earth or very low gravity dam, upto height of 8 meter.
Clay foundation
This foundation may be accepted for earthen dam after special treatment.
Availability of Materials
In order to achieve economy in the dam, the materials required for its construction must be available locally at short distance from the construction site.
Spillway Size and Location
The cost of constructing a separate spillway may be enormous or sometimes suitable site for construction of spillway may not be available. In such cases combining the spillway and dam into one structure may be desirable.
Earthquake Zone
If dam is located in earthquake zone, its design must include the earthquake forces.
Height of Dam
Earthen dams are usually not provided for height more than 30 meter. Hence for greater height, gravity dams are generally preferred.
Other Consideration
It includes life of dam, the width of roadway to be provided over the dam, overall cost of the construction and maintenance.
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