Full-Scale Performance Evaluations of Rock Check Dam Configurations under Channelized Flow Conditions

Ditch check practices, including rock check dams, are used on construction projects to slow runoff in channels to non-erosive velocities through impoundment formation. Despite the widespread use of rock check dams on highway construction projects, limited research has been conducted on performance improvement. This research aims to determine the effectiveness of the Iowa Department of Transportation standard rock check dam and develop efficient, cost-effective modifications through full-scale testing. Testing was conducted at the Stormwater Research Facility at Auburn University in a channel representative of Iowa highway construction roadsides with a bottom width of 10 ft (3.0 m) and a depth of 5 ft (1.5 m). The data collection included impoundment length and depth, flow velocities, and dewatering time. The results of the standard installation indicate little impoundment formed upstream, an average of 5.9 ft (1.8 m), showing that over 90% of the channel would be subjected to erosive flows. Increased performance and reduced costs were achieved through modifications. An installation with a removed excavation, a smaller rock gradation, a geotextile overlay with dewatering holes, and a reduced width along the flow direction increased average impoundment to 57.5 ft (17.5 m) and reduced approximate material cost by 55%. The additional impoundment formed due to the geotextile overlay also increased sediment capture during sediment-laden evaluations from 9.4% captured by the standard installation to 72.4% and lowered average discharge turbidity by 396 NTU. Implementing improved rock check dam installations will prevent soil loss in conveyance channels and reduce costs.