Pennsylvania was once a landscape of green, but as development altered the land, it also affected the water regime. Runoff became an issue, so basins were created as a standard "stormwater management" tool. Much like giant bathtubs, basins were designed to fill up in heavy storms and keep water at bay. That was then.
Today, it's pretty well acknowledged that traditional basins are not very effective. The good news is that there are a number of retrofits that can make them perform more naturally and help prevent flooding, filter pollutants, and get water back in to the ground.
Watch on StormwaterPA.org to get more tips for managing runoff from rain: stormwaterpa.org/rethinking-basins.html