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.
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.