ponding basin 

An open field, usually covered with grass, about the size of a football field or larger that is sunken into the ground ten feet or more from the surrounding land. Some storm drains empty into a ponding basin. They help deal with runoff to prevent flooding. The edges are usually somewhat steep, and if they are high enough, they can be used for sledding.

We flew kites in the ponding basin, even though the ground was a little moist.

ponding basin by Muthah Monkee May 25, 2004