Which of the following is considered a diversion method for rainfall runoff?

Perimeter dikes are an effective diversion method for rainfall runoff because they are designed to intercept and redirect the flow of excess water away from vulnerable areas, such as construction sites or agricultural lands. By creating a raised embankment around the perimeter of a project area, perimeter dikes help in controlling the movement of water, thereby reducing the risk of erosion and sediment transport into nearby water bodies. This proactive approach effectively manages rainfall runoff, maintaining site integrity and minimizing environmental impacts.

Concrete lined channels, rock lined waterways, and grassed waterways do play roles in managing water flow and reducing erosion, but they primarily focus on conveying water rather than specifically diverting it away from areas prone to runoff issues. Their main function is more about enhancing the stability and capacity of existing watercourses rather than serving as barriers to redirect water. Thus, while they contribute to overall stormwater management strategies, they do not represent diversion methods in the same targeted manner as perimeter dikes.