What component is placed in dry swales to help manage stormwater flow?

The component placed in dry swales to help manage stormwater flow is check dams. These structures are designed to slow down the flow of water, which helps facilitate sedimentation and allows for better infiltration and treatment of stormwater. By creating small obstructions along the swale, check dams create ponded areas that temporarily hold water, allowing sediments and other contaminants to settle out before the water continues flowing downstream.

In contrast, the other options, while they may play roles in stormwater management, are not specifically associated with dry swales. Biofiltration media is often utilized in biofiltration systems where water is treated as it passes through the media, but it is not a physical component specifically used to manage flow in dry swales. Permeable pavement is a surface material that allows water to infiltrate through it, primarily used in areas like parking lots and driveways rather than within swales. Litter traps are used to prevent debris from entering waterways, but they do not directly influence the flow within a dry swale. Thus, the utility and design of check dams in dry swales make them a critical component in effective stormwater management practices.