I had fun today. My goal was to create a nice pool in the middle of my meeting area for my dwarves. So what I decided to do was make a hole in the ceiling that would allow a tunnel from the river to come in and fill the channelled out pool. I would then throw a lever and cut off the flow of water. It would have worked fine, if I had not forgotten that things can travel diagonally. Needless to say that poorly placed floodgate caused my fortress to flood. Dwarves began moving stockpiles, trying to salvage everything of value, while my miners feverishly dug channels to slow the rising waters. I managed to get a floodgate up by repeatedly touching it (took a damn 10 minutes IRL). Unfortunately my entire fortress was more or less underwater. Luckily While digging I came across the first cavern. This was exactly what I needed. This was the drain to my figurative dwarf bathtub. I tunnelled underneath the original pool which just happened to be on the edge of the cliff descending into the cavern, and made a single upward ramp. Immediately water began rushing down into the caverns, I watched as water flushed out of my fortress and into the caverns below. Now what I did not know was that my dwarves were now being sucked into a whirlpool. I got notification after notification saying that Urist McWeakswimmer died from colliding with an obstacle. Caverns began to fill with blood as more and more dwarves got sucked down the drain, being pounded against the rock walls on their way down. When the water in my fort receded leaving only mud, I had lost about 12 dwarves to the hell drain. But at least after all the chaos, the weather cleared.