Boulder Weirs contribute to a number of important functions in the aquatic environment. They:

• Reduce water energy and therefore reduce erosion potential.

• Combinations of pool and riffle sections improve aquatic habitat by adding oxygen to water and providing pools to live in.

• Water elevation is raised so streambanks are not quite as tall and therefore do not collapse as easily.

• Weirs can slow or stop channel downcutting so more stable channels develop.