Stream assessment for multicell culvert use

Although culverts have traditionally been an economical means of conveying stream flow at a road crossing, they can hinder fish and wildlife passage in the channel and on the floodplain and can create or augment localized channel instabilities. A possible solution to these problems is to use a multiple-cell arrangement, in which one or more culverts placed in the channel convey all flows up to the dominant discharge and one or more culverts positioned in the floodplain convey overbank flows up to the design discharge. This arrangement results in a reduction of flow concentration through the culvert and a properly functioning floodplain, thereby improving fish and wildlife passage and reducing erosional problems. For this system to function properly, a well-established and active floodplain is required; the multicell system will not perform adequately in an incised channel. In this paper, a method to determine appropriate physical environments for multicell culvert systems, based on stream-channel stability and stage-of-channel evolution, is presented.