A modular in-stream barrier structure to limit upstream
Dale E. Miller,* Mainstream Restoration, Inc., 321 E. Main St., Suite 401, Bozeman, Montana
Paul Sanford, Allied Engineering Services, Inc., 32 Discovery Drive, Bozeman, Montana 59715
Fisheries management objectives that include segregation of native and introduced fish
species often depend upon installation of a physical in-stream barrier with a long functional
design life. Fish barrier sites are typically located in remote locations and reflect varied
topographic and hydrologic conditions. A modular fish barrier, consisting of commercially
available pre-cast concrete box culverts and slabs, was developed for relatively low-cost,
permanent installations at multiple locations around the State. The barrier is comprised of
upright culverts connected to form a weir and abutments and slabs to form splash pads.
Structural design elements include: weir width; abutment height; and structure stability
against overturning. Passage impedance design elements include: weir height; preventing pool
formation at the structure base; and restrictive velocity when leap constraints are exceeded.
Topographic design elements include: channel-to-weir transitions and grading between the
abutments and adjacent ground. This barrier has recently been installed on Whites Gulch near
Canyon Ferry; barriers on Seepay and Magpie Creeks near Dixon and Cottonwood Creek
near Wolf Creek are in various design phases. This paper presents the basis for the structural,
passage impedance and topographic design elements as well as design lessons learned from
the installed barrier.