Editing 40d:Floodgate

A '''floodgate''' is an object used to regulate the flow of fluids, such as [[water]] and [[magma]]. It is not the ''only'' item that will do so, and in fact is often not the best choice - [[door]]s, [[hatch]]es, and [[bridge]]s also work, often better, depending on the circumstances and needs. (See [[Floodgate#Floodgates vs other barriers|below]] for a comparison.)

They can be manufactured from [[rock]] (at a [[mason's workshop]]), [[wood]] (at a [[carpenter's workshop]]), [[metal]] (at a [[metalsmith's forge]]), or [[glass]] (at a [[glass furnace]]). Once manufactured, they are built in the desired location by using the keys {{k|b}}, {{k|x}}. 

Unlike doors or hatches, they cannot be opened at the time they are built - they ''must'' be linked with [[mechanism]]s and activated remotely if they are to open and close.

== Placement ==
Floodgates must be built on solid [[floor]] (i.e. not over a channel), but unlike doors do ''not'' have to be attached to a wall.  A long line of free-standing floodgates can create a removable wall, that completely disappears when they are "opened".  Dwarves must be able to stand [[orthogonal]]ly to the floodgate in order to build it. In order to control a vertical water flow from a lower source, one solution is to build the floodgate on a constructed [[wall]], and then remove the wall.

Floodgates generally have to be built prior to flooding the area (obvious for [[magma]], isn't it?) but can still be built at a [[water]] level of 1/7. They are placed in a "closed" position, and if they are to be opened they must be linked to a [[lever]] or [[pressure plate]] - this can be done after liquid is introduced to one side, so long as the other side is accessible.  

If there is no roof above a floodgate nor above an incoming water flow that comes from a source with higher elevation, the water can spill over the floodgate. See the [[pressure]] article for more information.

[[Dwarves]] often like to stand on the wrong side of the floodgate they are constructing so that they may conveniently decline any subsequent labor. They'll sit there with their feet propped up on a convenient rock, twiddling their thumbs until such time as the floodgate is opened mechanically or deconstructed. To avoid this situation you should build something on the tile you ''don't'' want them to stand on, <tt>Suspend</tt> its construction until the floodgate is complete, and <tt>Cancel</tt> its construction when you're finished.

====Placement with existing water====

Dwarves will not place any object in water deeper than 1/7 ("area flooded"), so if attempting to control an existing flow (ie, if the flood has already occurred), you will need to [[dam]] the water to place your floodgates (or doors, or bridges, etc). 

== Activation ==
Floodgates have to be linked to [[lever]]s or [[pressure plate]]s to allow them to be opened and closed <s>remotely</s> at all. An open floodgate also can be walked through, whereas a closed one can not.
Once activated, it will take approximately 100 steps for the floodgate to open or close: the same as [[bridge]]s.

One serious flaw with floodgates is that if ''anything'' is in the tile with them when they are signaled to close, they will ignore that signal and remain open. "Anything" means '''any object''' - a sock, a butterfly corpse, a goblin, a crossbow bolt, anything! The exception to this rule is that floodgates will close on fluids (water and magma), and destroy (not displace) any units of liquid on the tile.

Because levers have on/off states rather than simply toggling attached buildings, the lever/pressure plate must send two more signals in order to unstick a floodgate - one to open (which does nothing, as it is already open) and a new "close" order - and hopefully that works.  

== Floodgates vs Magma ==
Closed floodgates of any material will resist [[magma]], much like constructed [[wall]]s. However, once a floodgate is opened, the magma will flow though and destroy:
* the floodgate itself if it was not made of [[magma-safe materials]].
* the [[mechanism]] if it was not made of [[magma-safe materials]] ([[bauxite]] or [[raw adamantine]]), thus deconstructing the floodgate.

== Uses ==
A water floodgate connected to a [[river]] can be opened to create a shallow pool, then closed, the pool then be drained or allowed to evaporate. The resulting [[mud]] can be used for [[underground]] [[farm]]s. Standing water can be used for drinking, or sufficiently rushing water used as a defense against invaders.

A floodgate can also be used to cover [[fortification]]s when they are not being used. This will prevent enemies from firing into your fort through the fortifications, and can be useful if your [[marksdwarf]]s arrive at the fortification one at a time.

Unlike doors, floodgates can be built directly adjacent to each other; that is, floodgates do not require an adjacent wall. This allows [[channel]]s wider than two squares to be regulated. This characteristic also permits for the construction of "siege doors", allowing areas wider than two tiles to be sealed off from the enemy. For instance, the three tile wide access point for a [[Trade Depot]] within the fortress can be closed down into a chokepoint with floodgates and a lever, giving your marksdwarves more of a chance to shoot invaders.

Using floodgates to halt or reroute enemies must be planned carefully, as large creatures such as [[Troll]]s can destroy floodgates. One solution is to use a bridge over a channel. It can still be controlled by a pressure plate or lever, but prevents trolls from ignoring your carefully planned defences.

==Floodgates vs other barriers==

{|cellpadding="2" border="1"
! Barrier !! Jammed<sup>1</sup> <br />by item? !! Pros/Cons || Activation<br /> Delay<sup>3</sup>
|-
|  Floodgate || Yes || Can be built in a line without support <br />Closed when installed, un-openable until linked || 100 steps
|-
|  [[Door]] || Yes || Spare doors are often readily available,<br />Require support - only 2 wide max <sup>2</sup> || Instant
|-
|  [[Hatch]] || Yes || Spare hatches are often readily available <br />Only good to control vertical flow || Instant
|-
|  [[bridge|Drawbridge]] || No || Opens/closes opposite of any of the above <br />Can control vertical or horizontal flow, or both <br />Un-jammable  || 100 steps
|-
|  [[bridge|Retracting Bridge]] || No || Only good to control vertical water flow <br />Will not destroy/kill anything in its area<br />Un-jammable   || 100 steps
|-
|}
Notes:
:1) Some barriers refuse to close when any item, ''no matter how small'', is blocking them.  Drawbridges destroy anything that is in in their "landing area" when they open, and anything on their "anchor point" when they close.
:2) There is an exploit that can work around this limit - see [[Door#Free-standing_doors|free-standing doors]].  However, a Caravan path is still blocked by doors, even 3-wide, even when open.
:3) The delay between the activation of the [[trigger]] (lever or pressure plate) and the response of the barrier. A "step" is one step that the game advances, not a step that a dwarf takes (which takes a variable amount of "steps").


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