A weir is a small dam built across a river to control the upstream water level. Weirs have been used for ages to control the flow of water in streams, rivers, and other water bodies.

For years, the lock and dam have been at the center of a controversy ... The corps wants to replace the lock and dam with a rock weir – a low barrier in the water – to control the flow ...

A dam is structure built across a river to hold water back, it can be used to store water, control flooding or make electricity. A weir is similar to a dam but it is a lot lower. Dam Removal ...