Case Study: Gabion Weirs (Bullhead City, AZ)

Desert Foothill Estates was subdivided in 1995 by Bullhead-Laughlin Land and Development Company. The 540 acre parcel of land is located in the north end of Bullhead City, AZ, on Bullhead Parkway, about two miles from the Colorado River Bridge. This section of land was divided by "inset alluvial fans", typical of the washes along the west side of the Black Mountains, that outfall into the Colorado River.

Gabion weirs

The project consisted of two channels, Black Wash South and Black Wash North, which join approximately at the center of the development. At this location, the storm waters are conveyed by Highland Wash, a channel constructed as part of the Mojave County Airport/Bullhead City Flood Control Project, to the Colorado River. Several flood control alternatives were investigated and channelization of the two washes was selected. The natural slope of the area is approximately 3 to 4 percent.

Filling gabion baskets

Gabions were selected for the drop/energy dissipater structures required to set the channel grade at the equilibrium slope for sediment transport through the unlined channel bottom.

Filter fabric behind weir

Black Wash South has a 100-year peak discharge of 2,300 cfs, and Black Wash North has a 100-year discharge of 3,060 cfs. Eleven weirs and two outlet structures were installed. The gabion weirs are 100 feet wide with vertical drops of three to four feet.

Outlet structure

The weirs have a 24 foot stilling basin of 18 inch gabions and an 18 inch high counter-weir with a 6 foot cut-off wall. The channel invert has natural soils with rip-rap on the banks. The gabion weirs and the rip-rap channel banks are lined underneath with a non-woven filter fabric.

Gabion weir