Evaluation of Rock Check Dam Configurations using Large-Scale Testing Techniques

This will be a presentation on large-scale evaluations of rock check dam configurations and improvements to current standards used by Iowa DOT. Participants will learn the importance of rock check dam efficiency and the methodology for evaluating rock check dams.

Rock check dams are an erosion and sediment control practice implemented during construction to reduce channel velocity and promote sediment capture. Rock check dams consist of revetment stone rated for high-velocity flow. These practices are widely used in construction, yet minimal research has been conducted on their performance. The primary goal of this research topic is to increase the impoundment length upstream of rock check dams. The improved impoundment will increase sedimentation and decrease downstream erosion. Research will provide the opportunity to optimize the design for increased efficiency and reduced costs. The Iowa DOT maintains a standard detail for rock check dams consisting of class D revetment stone. The current standard is placed in a triangular distribution over a 6 in. excavation with an engineering fabric underlay. Aggregate is stacked a minimum of 2 ft above the original ground line with 1.5H:1V side slopes. The modifications to be evaluated include (1) the Iowa DOT standard with the addition of an engineering fabric overlay, (2) the Iowa DOT standard with the addition of an engineering fabric overlay and no excavation, and (3) a trapezoidal distribution with 3H:1V side slopes and an engineering fabric overlay. Testing will be conducted in a channel designed to Iowa DOT standards. The properties analyzed will be the water turbidity upstream and downstream of the rock check dam. With this, sedimentation profiles will be created and used to determine the performance of the check dams. This data will allow for recommendations to be made based on the performance of check dams and the cost of each modification.