Stormwater channels are specially designed pathways that guide excess rainwater away from streets, parking lots, and other urban surfaces. They can take various forms, including open ditches, swales, and culverts. The primary purpose of these channels is to direct stormwater toward drainage systems or natural water bodies, thereby preventing water accumulation that can lead to flooding.

Manholes are in essence man-made holes, Nelson told Live Science, and these are typically made from rotational tools, which tend to make circular shapes. So, a circular shape covering the manhole would be the best fit in terms of functionality. Anything else would be more complicated and less economical. 

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