A river runs through it–sometimes. Our picturesque meadow may seem very natural, but it is actually meticulously designed and engineered to serve a practical storm water management purpose. It captures runoff so that the land can reabsorb it. Unlike conventional stormwater management systems, the meadow doesn’t simply control the rate of outflow, it frequently prevents it altogether. The stormwater is returned to the aquifer.
Here is an illustrated article that gives all of the details.