Looks like a pond to help control the stormwater from the parking lot. Ponds like that, and most man made ponds, need to be cleaned out occasionally. Otherwise they fill in completely with sediment and serve no function. Some storm water ponds are also regulated by the ministry of environment which state how often they need to be cleaned out in order to still work.
As it was man made to start with, I would assume that in a couple years it will get back to that "naturalized" look.