Dam and Reservoir Design

An engineering design must be created before a reservoir and dam can be constructed. The design will take into account information provided by hydrologists, geologists and surveyors on how the water and surrounding land will behave and change once a reservoir and dam are built. It should be noted that a berm and a dam are two completely different structures . 

There are four types of dams: embankment, arch, gravity and buttress.

What is a berm?

A berm is a man-made sediment barrier placed at the edge of a slope or a wall built adjacent to a ditch to guard against potential flooding.

Berms are placed in flood-prone areas to protect against erosion, run-off and high water. Berms typically are made of compost, mulch or gravel materials because their density enables them to slow down and retain floodwaters. 

Click here for more information on berms.

Embankment

Dam Type Characteristics
Embankment
  • Primarily made of soil or rock that is found locally.
  • Erosion is a major concern for these dams; continuous maintenance (such as vegetation control) is required.
  • A cross section will look like a bank or a hill.
  • Most have a central section made of impermeable material to stop water from passing through.
  • Embankment dams can be either “earthfill” or “rockfill”.
  • Earthfill dams are the least expensive type of dam to build, are made of clay and compacted earth, and are relatively small and easily eroded.
  • Rockfill dams are constructed from materials from the reservoir site and work well in cold or rainy conditions.
Photograph of an embankment dam

“Embankment dam” by CameliaTWU is licenced under CC BY 2.0. No changes were made to photograph.

Arch Dam

Dam Type  Characteristics 
  Arch
  •  Made from concrete with steel support.
  • Used for on-stream storage where water will flow over the top of the dam. 
  • Resilient to erosion.
  • Consequences of over-topping (when water runs over the top of the dam) can be potentially catastrophic depending on design. 
  • Arch dams are supported by abutments, anchors and a solid geological foundation.
  • Arch dams are used in narrow valleys with solid rock foundations. Typically arch dams are very tall. 
Overhead view of an arch dam and reservoir
Photo by Francisco Kemeny on Unsplash

Gravity Dam

  Characteristics 
  Gravity
  •  Made from concrete with steel support.
  • Used for on-stream storage where water will flow over the top of the dam.
  • Resilient to erosion.
  • Consequences of over-topping (when water runs over the top of the dam) can be potentially catastrophic depending on design. 
  • Gravity dams are supported by abutments, anchors and a solid geological foundation.
  • Gravity dams are very large. Most gravity dams constructed since 1980 used a specific method of building. These dams are called Roller Compacted Concrete dams (RCC dams) because the dam is built in thin layers and a roller compacts the concrete after each layer is added. 
  • A cross section of a gravity dam will look triangular.
Photograph of a gravity dam and reservoir
Photo by Tejj on Unsplash

Buttress Dam

Dam Type  Characteristics 
  Buttress
  • Made from concrete.
  • Must be constructed on sound rock.
  • Buttress dams are supported by triangular shaped walls (“buttresses”).
Photograph of a buttress dam
Photo by AlaDin Habboubi on Unsplash

Sources

[1] HydroCoop. (2013). Dam design and construction, reservoirs and balancing lakes. Retrieved from: http://www.hydrocoop.org/dam-design-construction-reservoirs-balancing-lakes/

[2] The British Dam Society. Dams and Reservoirs. Retrieved from http://www.britishdams.org/student_zone/documents/BDS_Fact%20Sheets_version_low%20Res_Web.pdf

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