How Do Dams Prevent Flooding?

Dams are an important part of flood protection for any city. They protect against the potential loss of life and property that can be caused by flooding. After a severe storm that brings heavy rainfall or wave action, such as a hurricane or tsunami, dams can help make a huge difference in preventing flooding. Here's a deep dive into how exactly dams help protect against flooding.

How Dams Prevent Flooding

Dams protect against flooding by collecting and holding water when it reaches a certain level. Once collected, a dam is usually designed to release the water back into the river at a controlled speed. However, some dams are designed to divert the water elsewhere for other uses. 

How flow-through or perforated dams work

One example is a flow-through dam, also known as a perforated dam. Flow-through dams are built solely for flood control and are used to protect against flooding in downstream areas. Because this type of dam is built solely for flood control, the opening (i.e., "spillway") is at the same level as the riverbed. This means that when there isn't excess water, the river will continue its natural flow. However, when water levels rise, the dam slows the water flow through the opening to prevent flooding. 

Understanding How Flow-Through Dams Protect Your Area from Flooding

If you live in an area prone to flooding, flow-through dams are probably installed along major rivers. One of the biggest benefits of perforated dams is that they also prevent the flooding of farmlands. This offers a broad blanket of protection where a flood could otherwise destroy a city's infrastructure and the residents' livelihoods.

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How Reservoirs Work with Dams to Help Prevent Flooding

Reservoirs also play a major role in flood prevention. They regulate river flows by containing different volumes of floodwaters and then provide a controlled, timed release of water. A reservoir differs from a dam in that it's an artificial lake built for the purpose of storing excess water. 

In many cases, reservoirs can be formed by constructing numerous dams across an area's rivers. However, some reservoirs are constructed from natural lakes. This type of reservoir has its outlet dammed in order to prevent water from escaping naturally and to control the overall water level. Through control of the dam, the water flows out of the reservoir at desired speeds and increments. Together, reservoirs and dams greatly help reduce flooding in many areas.