Things started going downhill when the human caravan arrived.
At the time, I was draining both rivers so I could collect all the goblinite from the last few sieges that had been washed away by judicious use of draining and releasing one of the two rivers. So my FPS took a huge hit.
Then an ambush or two showed up. They were dealt with quickly, but the humans decided to get the hell out of there. In the middle of their retreat, another siege showed up. Things went relatively well, all things considered... I released the rivers, called everyone inside, and waited it out. Most of the goblins wound up dead, washed over the falls or slaughtered by the humans or caught in my myriad cage traps.
A few survived, though, clinging to walls in the river. I didn't think much of it, assuming they'd drown or get washed away like all the rest had eventually.
They had other ideas.
While I was rescuing goblinite and humanite from the battlefield, two hammer goblins arose dripping from the river and proceeded to annihilate nine or ten of my hundred and sixty dwarves in quick succession. They eventually fell victim to cage traps, but not before someone started tantruming over the loss of his wife and children. (It's not my fault, you fucking idiot! You were the one who married the dipshit and had twelve kids with her!)
I decided to wall off the river so this wouldn't happen again. While walling sections of river, though, my masons disturbed a crossbowman who crawled dripping from ambush and proceeded to one-shot seven dwarves AFTER RUNNING OUT OF ARROWS[/b] before he, too, fell to a cage trap.
Things had not yet reached tantrum spiral mode, but they probably aren't far from it now.
A dragon just showed up.
I believe this is the most fun I've ever had!