What component is found at the end of a culvert to enhance its performance and stability?

The component enhancing the performance and stability of a culvert at its end is the headwall. A headwall is a structure that provides support and protection to the culvert's opening. It serves multiple functions: it offers structural integrity, prevents soil erosion, and helps direct water flow into the culvert, minimizing turbulence and potential damage to the culvert and surrounding area.

Additionally, the design of a headwall can accommodate different inlet configurations and ensure that the flow is properly aligned with the culvert, thereby optimizing hydraulic performance. By doing so, it helps in managing the transition between the culvert and the natural stream or drainage channel, which is crucial for maintaining the overall efficiency of the drainage system.

In contrast, the other options serve different purposes and are not typically found at the end of a culvert. For instance, a parapet is often used as a safety barrier along elevated structures, a toe wall is located at the base of a slope to stabilize it, and an end sill typically assists with flow transitions rather than providing the structural benefits that a headwall offers.