Design of Nature-Like Fishways for Small Dam Projects

摘要

Existing dams and weirs constructed across streams result in obstruction to fish migrations. As such, fish access to spawning grounds and other habitat areas is prevented. Fish habitat conservation measures often require that fish passage facilities be constructed at the site of the obstruction. For the most part, fish passage facilities have been comprised of hard-engineered structures or other facilities. More recently, however, increasing attention has been given to the use of nature-like fishways for such passage. Two types of nature-like fishway are distinguished, namely the pool and riffle type and the rocky ramp type. The pool and riffle fishway is arranged in a stair-step configuration, with short steep reaches (riffle) connecting somewhat longer flat reaches (pool). The rocky ramp fishway is comprised of a long sloping section of channel, usually accompanied by resting areas provided by large boulders. In most instances, both types of nature-like fishway may have application to small dam or weir projects in which the elevation change is relatively small. This paper presents a discussion of nature-like fishways, with specific focus on several aspects of their design. Included in the paper are an overview of the nature-like fishway concept, a detailed discussion of suggested design requirements and methodologies, and a summary of some research needs for improving the concept.