A low head dam, also known as a run-of-river or diversion dam, is a structure built across a stream that allows water to flow over its top. These dams were most often used to divert water into canals for purposes like running mills, generating electricity, or irrigation. However, they can cause significant impacts on the environment by blocking the movement of water, sediment, and aquatic organisms.  These can lead to negative changes to the characteristics of the stream and habitat.