Types of Dams | What are the types of dams?
Dams are commonly made up of earth or concrete, depending upon the geology of the area. Dams of different types may be constructed across river valleys and are described below.
1. Gravity Dam
It is also known as a concrete dam. In this type of dam, the axis is straight or slightly curved (Fig. 9.3).
These dams resist the thrust of water by their weight; gravity dams are massive concrete structures. The foundation rock of the dam should be very strong so that the load of the dam may be borne by the rock. Example: Bhakra Dam.
2. Arch Dam
In this dam, the length of the axis is curved and less than the height of the dam (Fig. 9.4). The arch-shaped structure is made of concrete, with its convex side facing upstream.
The thrust of water in the reservoir is transmitted to the walls of the river valley on either side of the dam. Arch dams are, therefore, constructed when valley walls are quite strong.
The areas having a steeper slope in the hilly region are locales for the construction of such types of dams. Example: Idduki Dam (Kerala).
3. Buttress Dam
The dam which is characterized by a series of girders and concrete panels parallel to the axis of the dam is known as a buttress dam (Fig. 9.5).
The buttresses are constructed at the downstream side to support an upstream deck. The foundation rocks should be quite strong.
4. Earth Dam
They are made with clay, silt, and alluvial materials that are available in the river valleys and adjoining areas of the proposed site of construction (Fig. 9.6).
These dams can be constructed on earth or on poor rocks.
5. Rock-Fill Dam
The dam has a trapezoidal shape and is filled up with gravel, pebbles, and boulders (Fig. 9.7). This type of dam is constructed in high seismic zones. Example: Salal Dam in J&K.
6. Masonry Dam
The dam which is constructed from bricks, boulders, and stones, which are non-reactive and nonporous, is known as a masonry dam.
In this dam, the materials are used in such a way that permeability is totally negligible (Fig. 9.8). Example: Srisailam Dam in Andhra Pradesh.