Can't tell for sure, but that looks like gasket-joint pipe. Likely wasn't given proper support at the bottom when it was installed.
The pipe slid down the slope of your dam and exposed the gasket, which resulted in failure of the seal.
I see a couple temporary buy some time while you decide on the best fix options.
It's already been suggested to attempt re-seating the joint by moving the lower section of pipe up the slope. I would try that
first, but I wouldn't kill myself on it. If it moves good, or doesn't move no big deal - make one end-to-end cut in a Fernco
coupling so that it can be opened up and wrapped onto the pipe joint. Wiggle the Ferno onto the pipe, slather the joint with
silicon gasket compound, slide the Ferno in place, install the band clamps and tighten that sucker down.
Or... cut the damaged joint completely out of the pipe, then use two Fernco couplings and another section of pipe to bridge
the gap that was left by cutting out the joint. This method would not require splitting the couplings to install them on the pipe.
https://www.fernco.com/dimensional-drawings/plumbing/flexible-couplings/stock-couplings-1001/1001-65
