Storm Drains

Rectangular storm drain with a small percentage of maximum flowrate capacity being utilized.

Today, as I was riding home on the transit, I noticed a storm drain with water pouring in it after a light shower. I did not just see water pouring in a drain but I was mindful that the maximum volumetric flowrate that a circular drain could handle was dependent on the diameter of the drain. For square or rectangular drains the maximum volumetric flowrate capacity is dependent on the length and width of the sides. This is important because if the volumetric flow of water entering the drain exceeds the maximum flow capacity  then water can begin to accumulate and cause flooding.