so... I have a neat little fort started on a peninsula on a lake, and I have a little castle above ground and a gap int eh aquifer I managed to hit going down to solid rock.
I make a moat around the castle, and remove all the ramps (and I made the moat go wide around the farms one layer down, face palm averted!)
face palm 1: I left a ramp so the miners could get out of the moat- but I didn't leave a way to get back in to the fortress... my miners hang out down there for a month or two before I figure out why and construct some floors bridging the moat.
face palm 2: I'd built the floors to get my miners back inside and keep them from dehydrating, and I rebuilt them off to the side of my entrance, then built the bridge next to it, then finally deconstructed the floor tiles... all at once. atleast one tile ends up supported only by the bridge, caving in and taking one of my miners (and starting seven) into the moat where he breaks a leg and botha rms and damages his liver.
face palm 3: I hastily construct a hospital for my miner, and enable the various healing labors on what migrants happen to have come with them (no diagnostician, a random dorf gets picked as chief medical dorf and diagnostics enabled) but I had no dorf with skill in suturing, so I didn't enable it on anyone... apparently, dressing and bone setting have to wait until suturing is done. I finally figure out why no one is caring for my miner after he is pale with infection (the stray kitten that fell with him succumbed to infection not to long before) and my miner succumbs to infection himself as the newly appointed suturer is just beginning his work.