Revolver_Ocelot on How do I revert the flood?

If that fails... Well, losing is fun, and you will learn to better water-proof your fortress in the future.

How to waterproof a Fortress to prevent massive headaches when a leak happens in the future, starting a flooding?

Version: 0.50 (Steam).

1 Answer 1


Section your fortress

Doors are a marvel of dwarven engineering. No matter what material they are made of: granite, grass, copper, talc, gypsum, ash — all of them are able to completely block any amounts of water forever (until a filthy kobold decides that this door would better look opened wide).

Before doing any expansion to your fortress, make sure that mining region is separated from the rest of your fortress by at least two separate layers of doors, with something like an airlock inbetween. Construct walls and install doors if nessesary. If aestetics require it, you can remove walls and doors later, after all digging is done and there is no danger of flood.

Do not rely on doors alone to keep water away

After all, they can be opened by someone, who does not care about you and your orders: tantruming dwarves, invaders, thieves... Use floodgates or raised bridges to keep water and dwarves separate. Do not repeat my mistake and leave doors to the magma stack freely accessible.


2-3 tiles wide line of grates leading to waterways terminating at caves or edge of a map (you can't dig out edge tiles, but you can carve them into fortifications, which lets water pass through). Even in the case of breach, water would drop into sewers, buying you time to wall off compromised section. (Just don't flood the fortress while digging sewers). Example schematics below

Top view
              ###  Fortress →
←Deadly flood ###← Floor grates

          ▒▒▒▒   ▒▒▒▒
          ▒▒▒▒   ▒▒▒▒
          ▒▒▒▒   ▒▒▒▒
          ▒▒▒▒ ↓ ▒▒▒▒
Towards the edge of the map

While better considered a megaproject, and not everyday solution, it is still helpful.

When working with water, learn it mechanics.

Sometimes you want to mess with water: for irrigation, to make a cool waterfall, hospital water source, drowning chamber, pond for fishing, obsidian casting chamber...

Learning water (and magma) physics can make this easier. Main thing to remember is that water is "pressurized": it will try to fill all layers up to the "source" layer, travelling up if nessesary. More about it can be read at https://dwarffortresswiki.org/index.php/DF2014:Pressure

Diagonal gaps neitralize pressure, preventing water from rising higher that its current layer.

  >>>>>        ▒   >  >  >
 4Z Pressure  ▒  1Z Pressure
  >>>>>      ▒     >  >  >

(Image taken from wiki article linked above. xZ pressure refers to how many levels water can rise, including current layer. 1Z means that water would rise up to this level and no higher)

Using this information, you can make water traps to stop any flood coming from a hallway:

▒▒▒▒▒▒\  OOO  /▒▒▒▒▒▒▒▒▒▒▒▒

(Side view, OOO is a pressure regulator like the one shown above, \ and / are stairs or ramps)

While this might not look good in the fortress proper, safeguarding mining tunnels or service hallways that way could save your fortress.

  • "2-3 tiles wide line of grates leading to waterways terminating at caves or edge of a map" Sorry, but, how would these waterways be like? Is is something that span through multiple elevations? Apr 26, 2023 at 19:08
  • @BsAxUbx5KoQDEpCAqSffwGy554PSah depends on your preferences and expected amount of incoming water. For a single-tile "ah, I shouldn't have broken this wall" a single z-level 3-wide corridor directly below main level should suffice. Apr 26, 2023 at 19:30
  • 1
    @BsAxUbx5KoQDEpCAqSffwGy554PSah edited in example schematics. Apr 26, 2023 at 19:56
  • 1
    Thank you, now I can understand what you proposed. As you noticed, I'm deeply interested in sewers. Not only they will look cool and be ingenious, they seem like the definitive solution. But you said they will just buy me some time: "Even in the case of breach, water would drop into sewers, buying you time to wall off compromised section." . Why are not they the ultimate solution? Apr 27, 2023 at 0:29
  • 2
    @BsAxUbx5KoQDEpCAqSffwGy554PSah Water in DF is pretty thick and moves relatively slowly. Depending on volume of incoming water and sewers size and position, you can have 7/7 tile of water directly under grates, even though waterway is almost empty, allowing some water to cross the grates. It is unlikely, but I prefer to be sure that I am safe even in extreme situations. Apr 27, 2023 at 0:37

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