Editing 23a:Cave river

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:''A miner has located an underground river.''

The '''cave river''' is the first major landmark you will find as you tunnel into the mountain. It can be found by digging east of your entrance, usually one to three screens away. It is between 5 and 8 spaces wide, and twists and turns between roughly 48 spaces from the cliff face to about 103 spaces from the cliff face. It is surrounded by [[limestone]] 1-2 squares deep on both banks. "Offshoots" of the river will contain either waterfalls or small chasms. These offshoots will stay inside the range of the river, that is, offshoots would appear on the left side only when the river bends far to the right.

:''A miner has struck water! Flee the mines!''

The cave river may flood your fortress when you first discover it, sometimes drowning your miner or other dwarves unlucky enough to be in the flood's path. This risk can be reduced by {{K|b}}uilding a door in the shaft behind your miner as he/she approaches the river. Higher [[mining]] skill also reduces the chance of a flood, though having a highly skilled miner by this point is highly unlikely unless you've been actively avoiding uncovering the cave river.

The underground river is an easy source of mud for farming. It will seasonally flood the ten squares nearest to it on both banks. These flooded squares will become mud once the waters recede. Any squares reached by the initial flood will become muddy as well, and can also be used for farming until the mud dries in winter.

==River monsters==
The cave river is a source of numerous threats, particularly lizardman invasions, and precautions must be taken to ensure that they do not put your fortress in danger. Once the cave river has been discovered, there is a 25% chance per season of monsters emerging to attack your dwarves regardless of their activity. If you have built any [[well]]s within 130 tiles of the cliff face, certain monsters have a chance to emerge from them instead of from the river itself (1% chance per valid well, minimum 10% and maximum 50%); wells deeper within the cave will be used by [[chasm]] creatures instead.

River monsters include:

* [[Frogman|Frogmen]]
* [[Lizardman|Lizardmen]]
* [[Snakeman|Snakemen]]
* [[Cave crocodile]]s
* [[Giant toad]]s
* [[Mud man|Mud men]]

Up to 4 of the above creatures can be found in any given cave river. All of them are capable of emerging from [[well]]s.

After the first 6 cave river attacks, all further attacks will consist solely of creatures with the [RIVERATTACK_MOUNTS] token (i.e. Frogmen and Lizardmen) - if no such creatures live in your cave river, then you will continue to be attacked by all of the different creatures living in it.

==Waterfalls and sinks==
Occasionally the river may join with water pouring in from a waterfall. Waterfalls appear at the top of offshoots that flow downstream (i.e. offshoots that point north). The center of the waterfall produces [[mist]], which causes a happy [[thought]] for each dwarf that comes into contact with it.

When the river splits, one branch will create an offshoot that ends in a sink. Sinks have the same appearance as a waterfall, but they produce no mist and are surrounded by a few chasm tiles. A dwarf that is swept into a sink drowns immediately and produces the message "... has fallen into a deep chasm."

==Floods==
The rising waters of the river each season can be dangerous to your dwarves and fortress, but this can be mitigated by careful planning:

* Build several bridges downstream from each other, so that dwarves swept away by the flood waters can pull themselves out. 
* Carve out along the banks of your river. This not only gives you farmable mud and places where tower-cap mushrooms can grow, it also allows sideways flowing water to push dwarves onto solid land. 
* Avoid building upstream from a sink. Dwarves swept into a sink or the chasm around it will be instantly killed. 
* Doors close to the river banks should be kept tightly closed (not pet-passable) if there is a danger of flood waters reaching a stockpile. This can be set initially or done right after the flood warning appears (and then reversed once the flood has passed). 
* You can use floods to dispose of unwanted refuse, as an alternative to [[refuse|chasming]] it. Create stockpiles for any items you want disposed of just above any diagonal section of the river. The natural floods will push the refuse into the river, just as if you chasmed it, but without angering any monsters. To keep floods from coating your bridge(s) with refuse, be sure to place the stockpiles downstream from them. 

==See also==
* [[Chasm]]
* [[Magma flow]]
* [[Fluids|Fluid dynamics]]

{{Category|World}}