(2025) Evaluation of Rock Check Dam Performance using Large-Scale Testing Techniques, SPR-RE24(007)-8H-00, 2025. Transportation, Department of
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SPR-RE24(007)-8H-00_FINAL_REPORT.pdf File Size:13MB |
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SPR-RE24(007)-8H-00_TECH_TRANSFER.pdf File Size:1MB |
Abstract
Conveyance channels are commonly used on highway construction projects to manage the flow of water through the project to downstream discharge points or stormwater detention practices. However, these channels can be at risk of erosion before stabilization due to high-velocity flows. A common erosion control practice in channels is a rock check dam, which aims to slow flow by forming impoundment upstream of installations. Based on common spacing guidance, if rock check dams do not impound to their full height, areas of the channel will still be subject to erosive flow conditions. Past research has indicated that a geotextile overlay or smaller choker stone is required to facilitate a full impoundment, particularly in low flow conditions. Despite the widespread use of rock check dams, very few standards include overlays or chokers or have been evaluated for performance. To evaluate the Iowa Department of Transportation (DOT) standard rock check dam installation and develop more efficient and cost- effective modified installations, a standard Iowa DOT channel located at the Auburn University – Stormwater Research Facility was used. Installations were subjected to channelized flow conditions that represent those found on Iowa highway construction projects; measurements taken during testing include water depth, flow velocity, impoundment length, and dewatering time. The Iowa DOT standard installation facilitated 4.2 and 5.9 ft (1.3 and 1.8 m) of impoundment under the low (0.85 ft3/s [0.024 m3/s]) and high (1.7 ft3/s [0.048 m3/s]), indicating that much of the test channel was subject to high velocity, erosive flows. Installation components such as the removal of the excavation beneath the installation, the use of a smaller rock gradation, the addition of a geotextile overlay, dewatering holes in the geotextile overlay, and reducing the width of the installation, were evaluated to determine the impact on performance and improvements from the standard. Adding a geotextile overlay and switching to a smaller rock gradation significantly increased impoundment length; the addition of dewatering holes in the geotextile overlay resulted in faster dewatering times while not otherwise adversely impacting performance. Additionally, removing the excavation beneath the standard rock check dam installation and reducing the width of the installation were not found to negatively impact performance while reducing the installation and material costs. A most feasible and effective installation (MFE-I) installed on grade with the Iowa DOT erosion stone, a geotextile overlay with dewatering holes, and a reduced width from 6 to 4 ft (1.8 to 1.2 m) increased impoundment lengths to 58.7 and 57.5 ft (17.9 and 17.5 m) under the low and high flow conditions, respectively. The increased impoundment formation also impacted performance under sediment-laden conditions, with the MFE-I capturing 72.4% of introduced sediment, while the Iowa DOT standard installation captured 9.4%. The addition of the geotextile overlay also impacted water quality performance, with the MFE-I having statistically significantly lower discharge turbidity than the standard installation.
| Item Type: | Departmental Report |
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| Keywords: | Erosion control, stormwater, ditch checks, rock check dams |
| Subjects: | Transportation Transportation > Materials Transportation > Research Transportation > Design and Construction Transportation > Environment Transportation > Environment > Water |
| ID Code: | 53595 |
| Deposited By: | Iowa DOT Research |
| Deposited On: | 11 Jul 2025 20:34 |
| Last Modified: | 11 Jul 2025 20:34 |
| URI: | https://publications.iowa.gov/id/eprint/53595 |