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 i n the channel and on the floodplain and can create or augment localized cha nnel instabilities. A possible solution to these problems is to use a multi ple-cell arrangement, in which one or more culverts placed in the channel c onvey all flows up to the dominant discharge and one or more culverts posit ioned in the floodplain convey overbank flows up to the design discharge. T his arrangement results in a reduction of flow concentration through the cu lvert and a properly functioning floodplain, thereby improving fish and wil dlife passage and reducing erosional problems. For this system to function properly, a well-established and active floodplain is required; the multice ll system will not perform adequately in an incised channel. In this paper, a method to determine appropriate physical environments for multicell culv ert systems, based on stream-channel stability and stage-of-channel evoluti on, is presented.