The British Dam Society
Caring for dams, people and the environment

About Dams

Back to opening pageSpillways & Outlets

Water falling over spillways

Water falling over spillways on
Claerwen Dam, Mid-Wales

Spillways are structures that either form part of a dam, or are found just beside one. They are used, when a reservoir is full, to pass floodwater safely, and in a controlled way, over a dam, around it or through it.

Next time you visit a dam, look for its spillway. Here are some of the different types you may see:

Spillways are not the only outlets for reservoir water. Other outlets are built into the dam or away from it to let water out for a number of uses. These are some of the different types of outlets: