v0.34:Drowning chamber

Drowning chambers are multipurpose rooms which can rapidly fill up with and be drained of water. An effectively built drowning chamber linked up to a dammed river or open to the ocean can be used to drown and dispose of invaders or other irates nuisances (as part of your defense strategy), or to capture large fish for butchering (as part of your fishing industry). As such it can be considered one very large, very effective trap; drowning chambers are indiscriminate, and will kill anything land-bourn from above that can't breath in water, making it a fantastic defense against megabeasts and the like.

Construction

Water flow

The first prerequisite of a drowning chamber is a large source of water (or, in the last case, magma) that can be easily rerouted, be it a river, a natural body of water, or a constructed reservoir. This can be achieved in a few ways. The easiest way is to simply construct floodgates leading into an ocean or lake, if one is on the map; simply dig a channel through toone tile away from the body of water, put a floodgate there, link it to a lever, pull the lever, dig a hole, and then pull the lever again to plug the hole for when it's needed. Repeat for increasing amounts of flow.

If you have a river on the map, you can dam the river to redirect its flow into your chamber. The difficultly of this is trivial if your river freezes over in the winter, but generally quite difficult otherwise, requiring either magma tricks or a lot of idle hands and a large collapsible chamber underneath; see dam for more information on that. You can always build a series of one-tile floodgates into the river wall as well, although this tends too have decreased flow.

A pump stack can bring water from a cavern lake up to the surface for use, although this would require a cistern to be effective. An even larger pump stack can bring magma up to the surface, and allowing you to convert your drowning chambers into melting chambers. After all, who needs water when you can turn your enemies into carbon fumes? Simply build a magma reservoir, link it to your chamber, and marvel in how it quickly disposes of anything foolish enough to enter. Note that if you build a magma death chamber you will need to do so with magma-safe materials.

Trapping

Once you have worked out your water supply, you need to work out the room. A military drowning chamber can be a simple secondary hallway leading into your fortress with bridges on both sides. Upon seeing the enemy, close down your main entrance while leaving the secondary open. Enemies will path to your fortress using the shortest route possible and walk in, at which point you can close the bridges, trapping them inside for the ensuing flood. Building destroyers like titans and werebeasts are unable to destroy the walls created by erect bridges, so this design works against most everything, even otherwise unassailable megabeasts.

Note that ambushes sneak onto the map in ambush, and must be spotted first. Leaving an entrance wide open to them into the heart of your fortress unwatched can spell your doom. Keep a sacrificial animal or watchtower or something near the entrance, to keep eyes on enemy ambushes.

A fishing drowning chamber is much simpler; simply cover the room in cage traps and open it up to your water flow. Note that a military death chamber can easily be adapted into a fishing chamber, but the reverse is not necessarily true.

Drainage

The final piece of a drowning chamber is its pumping mechanisms. You want to be able to empty out a drowning chamber for reuse and for making use of what the unfortunate victim were carrying upon their deathbeds. What's the point of a trap that only works once?

The simplest way to pump off excess water is a battery of wind-powered screw pumps. Simply build a windmill one tile above your pump to power it. Since it's going to be off most of the time (or not, if it's for catching fishies), build a floor hatch over the input tile and attach it to a lever for easy on/off commands. If you don't have any wind on your map, a water wheel can be substituted instead, but if there is no running water on your map this can be quite complicated.

Where the screw pumps drain off to is your decision. If you are using a cistern, run the water back into your water supply. You can dig a tunnel through to the map edge and funnel it out of your game. You can build a small waterfall and drop it back into the water source it had come from in the first place.

When used for fishing, the object is to filter water through, not fill and drain it all at once, although you will want to be able to drain it completely as well to.