Earthen Dam: Types, Construction And Benefits

Earthen dams have been an essential part of human civilisation for centuries, providing a reliable water source for agriculture, industry and domestic use. These dams are made from natural materials such as soil, sand, gravel and rock, making them a cost-effective and environmentally friendly solution for water management. Despite their widespread use, earthen dams are often misunderstood, and their benefits and limitations must be better known. Learn about the design, construction, maintenance, advantages and challenges of this type of dam.

See also: What is barrage? How is it different from dams?

What is an earthen dam?

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Earthen dams are constructed using natural materials such as soil, clay, and rock. These materials are compacted to form a barrier that holds back water, creating a reservoir or lake. Earthen dams can range in size from small structures used for irrigation or water storage to large dams used for hydroelectric power generation and flood control.

Earthen dams have been used for thousands of years and are still widely used today due to their low cost, ease of construction, and suitability for construction in many different environments. However, earthen dams also have some disadvantages, such as a relatively low strength compared to concrete or masonry dams and a tendency to erode over time due to water seepage.

Earthen dam: Types 

There are several types of earthen dams, including:

Embankment dams

This is the most common type of earthen dam, and it is constructed by building up a sloping wall of compacted soil or rock. The dam is typically wider at the bottom than the top, creating a large base that provides stability.

Rock-fill dams

This earthen dam uses rock or gravel as the primary building material. The rock is placed in layers and compacted to form a solid structure. Rock-fill dams are often used in areas where the soil is unsuitable for building an embankment dam.

Roller-compacted concrete (RCC) dams

This type of dam combines the best features of earthen and concrete dams. RCC dams are made by compacting concrete with heavy rollers, resulting in a dense and durable structure.

Arch dams

This type of dam is designed to resist the pressure of the water by arching inward rather than relying on the sheer weight of the dam itself. Arch dams are usually constructed of concrete and are often used in narrow canyons where the sides of the canyon provide additional support.

Buttress dams

This type of dam uses a series of supports, called buttresses, to hold up the dam structure. Buttress dams are often used in areas where the foundation is not strong enough to support the weight of an embankment dam.

Earthen dam: Design and construction

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The design and construction of earthen dams involve several key steps:

1. Site selection: The first step in designing and constructing an earthen dam is selecting a suitable site. Factors considered when selecting a site include the type of soil and rock available for construction, the location of groundwater, and the potential for earthquakes, floods, or other natural disasters.
2. Design: Once a site has been selected, the dam is designed using engineering principles to ensure its stability and safety. The design may involve determining the dam’s height, width, and shape, as well as the size and location of spillways, embankment slopes, and foundation filters.
3. Materials: The next step is to obtain the materials used to build the dam. It may entail the excavation of soil or rock or the procurement of concrete or other materials.
4. Construction: The construction of an earthen dam typically begins with the preparation of the foundation, including excavation and grading of the site and placing a foundation filter to prevent water from seeping through the dam. Next, the embankment is built, layer by layer, and compacted to create a solid structure. Spillways and other features are added as needed.
5. Testing and monitoring: Once the dam is complete, it is tested and monitored to ensure its stability and safety. It may involve instrumenting the dam with sensors to monitor its performance, conducting regular inspections, and performing routine maintenance.

Earthen dam: Benefits

Some benefits of earthen dams include:

1. Cost-effective: Earthen dams are generally less expensive than concrete or steel dams, making them a popular choice for small to medium-sized dams.
2. Flexibility: Earthen dams are flexible and can adjust to changes in the water level. They can also adapt to different ground conditions, making them suitable for various environments.
3. Environmental benefits: Earthen dams can provide habitats for wildlife, and they can also be used for recreational activities such as fishing, boating, and swimming.
4. Water conservation: Earthen dams can store large amounts of water, which can be used for various purposes such as irrigation, drinking water, and hydroelectric power generation.
5. Flood control: Earthen dams can help prevent flooding in areas downstream by impounding excess water during heavy rainfall.
6. Aesthetically pleasing: Earthen dams can blend in with the natural environment and can be designed to enhance the visual appeal of the surrounding area.

Earthen dam: Challenges and limitations

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Earthen dams have several challenges and limitations that must be considered when designing and constructing these structures. Some of these include:

1. Durability: Earthen dams can be subject to erosion and settlement over time, reducing their stability and safety. It is particularly true for dams built in areas with high water flow or heavy rainfall.
2. Seepage: Earthen dams are susceptible to seepage. Water can flow through the dam material. Seepage can lead to the erosion of the dam material and instability of the structure over time. Proper foundation filters and other seepage control measures must be incorporated into the dam’s design and construction to mitigate the seepage risk.
3. Earthquakes: Earthen dams can be vulnerable to damage from earthquakes, which can cause landslides, liquefaction, and other types of damage. Earthen dams must be designed and constructed to withstand the forces associated with earthquakes in the area to minimise the risk of earthquake damage.
4. Flooding: Earthen dams can be vulnerable to flooding, which can cause erosion and instability. Earthen dams must be designed and constructed to withstand the forces associated with floods in the area, including the proper sizing and location of spillways to minimise the risk of flooding.
5. Maintenance: Earthen dams require regular maintenance and monitoring to ensure their stability and safety over time. It may include monitoring for signs of settling or erosion, repairing or reinforcing the dam as needed, and performing regular inspections to ensure it is functioning as designed.

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