Types of Dams, advantages, disadvantages and classification

What is a Dam?

A dam is a structure built across a stream, river or estuary to retain water. Dams are made from a variety of materials such as rock, steel and wood.

Structure of Dams:

Fig 1 : Structure of Dams

Definitions:

Heel: contact with the ground on the upstream side

Toe: contact on the downstream side

Abutment: Sides of the valley on which the structure of the dam rest.

Galleries: small rooms like structure left within the dam for checking operations.

Spillways: It is the arrangement near the top to release the excess water of the reservoir to downstream side

Sluice way: An opening in the dam near the ground level, which is used to

clear the silt accumulation in the reservoir side.

Advantages of Dams:

Dams gather drinking water for people -> Water Supply

Dams help farmers bring water to their farms -> Irrigation

Dams help create power and electricity from water -> Hydroelectric

Dams keep areas from flooding -> Flood Control

Dams create lakes for people to swim in and sail on -> Recreation & Navigation

Disadvantages of Dam

Dams detract from natural settings, ruin nature’s work

Dams have inundated the spawning grounds of fish

Dams have inhibited the seasonal migration of fish

Dams have endangered some species of fish

Dams may have inundated the potential for archaeological findings

Reservoirs can foster diseases if not properly maintained

Reservoir water can evaporate significantly

Some researchers believe that reservoirs can cause earthquakes.

Classification of Dams

Classification based on function

Storage Dam

Detention Dam

Diversion Dam

Coffer Dam

Debris Dam

Classification based on hydraulic design

Overflow Dam/Overfall Dam

Non-Overflow Dam

Classification based on material of construction

Rigid Dam

Non Rigid Dam

Classification based on structural behavior

Gravity Dam

Arch Dam

Buttress Dam

Embankment Dam

Rock-fill dam

1 – Gravity dams

Gravity dams are dams which resist the horizontal thrust of the water entirely by their own weight.

Concrete gravity dams are typically used to block streams through narrow gorges.

Material of Construction:

Concrete, Rubber Masonry

Fig 2 : Example of Gravity Dam Design

Fig 3 : The Grande Dixence Dam in 2004, facing west and Mont Blava (Source Wikipidea)

2- Arch Dam

An arch dam is a curved dam which is dependent upon arch action for its strength.

Arch dams are thinner and therefore require less material than any other type of dam.

Arch dams are good for sites that are narrow and have strong abutments.

Fig 4 : Jinping-I Dam also known as the Jinping-I Hydropower Station or Jinping 1st Cascade

Fig 5 : Typical vertical elements of Arch dams

3- Buttress Dam

Buttress dams are dams in which the face is held up by a series of supports.

Buttress dams can take many forms – the face may be flat or curved.

Material of Construction: Concrete, Timber, Steel

Fig 6 : Design of buttress Dam

Fig 7 : Roselend Dam in France

4- Embankment Dam

Embankment dams are massive dams made of earth or rock.

They rely on their weight to resist the flow of water.

Material of Construction: Earth, Rock

Fig 8: Embankment Dam Design

Fig 9 : Cross-sectional view of a typical earthen embankment dam

5- Rock-fill dam

These types of dams are made out of rocks and gravel and constructed so that water cannot leak from the upper stream side and through the middle of the structure. It is best suited in the area where rocks are around.

Fig 10 : Mohale Dam, Lesotho: highest concrete-face rock-fill dam in Africa