The miracle of beaver engineering! Clicking on the above image will take you to a 360° look at the scene, in which you can drag around to turn.
I first saw this dam a few years ago. Beavers had used the terrain to their advantage: a river flows through the marsh, the terrain is very uneven and the beaver had decided to build this add-on to the marsh, taking advantage of this little hill. This raised the water level at this part of the marsh, but didn’t really affect the part humans were using as hiking trails. Then, because there is nothing more irresistible to a beaver than the sound of running water, they also decided (or felt compelled) to block the culvert in the nearby existing pond that humans walked beside and around which new upgrades to the park created seating areas and bird blinds. This has, in fact, been designated as a habitat for birds, with fields, trees, and marshland providing nesting sites in a world that is ever-encroaching on needed habitat for wildlife.
The area was flooded as the water climbed up the bank and turned walking paths into a place more suitable for canoes. Many huge, glorious trees died after prolonged submerging and the battle between humans and beaver was evident by the back and forth in water levels. Water over the banks, beaver winning; trails walkable, humans winning. Last year was a constant back and forth until the battle ended. The culvert remained free of branches and mud, the flooding ended. I hope the critters were merely relocated, but it became clear that they were no longer around. This dam gives further evidence: it is leaking. No respectable beaver allows its dam to leak for very long. However, the pool remains, providing added wetland habitat for a variety of species. A Canada Goose is currently nesting on what appears may have been the beaver lodge, in the middle of this pool. A variety of ducks paddle around this more private part of the pond system and kingfishers seem to love perching in the dead trees giving some shadow to the pool. The sounds of frogs , Red-winged Blackbirds and Common Grackles co-exist with the ever-present drone of highway traffic and sounds from the next-door industrial park and trains. This is, after all, still part of the city.