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[andrian]

So, I embarked at the head of a river, but this river had a tendency to never be full of water, so my dwarves and visitors would often path through it, much to my dismay and annoyance. This was especially annoying when visitors would spend entire seasons swimming in the river rather than pathing into the safety of my fortress to study or join in the inn's festivities. To fix this, I decided to build a floor over the entire river. To my surprise, this was possible, as apparently it is possible to build floors right up to the edge of the map. This was also a safety feature, as I was using the river as a water source for flooding what I hoped would become an underground tree farm, and did not want to leave the fortress vulnerable to attack via the plumbing.

Alas, I seem to have made a grave mistake. Now that the river has been completely floored over, it has dried up. I think I am going to have to dismantle my floor so that rain water can once again fill my river. Hopefully the river's ecosystem will not have been completely destroyed by my mistake and fish will return once the water has been restored. I am tempted to do a little SCIENCE here instead, though. There is an aquifer only a few z-levels further down. I could potentially pump water up into the river without removing the floors. Would this allow fish to return, as the water would be over a river bed and would be flowing off the edge of the map?

[Thatotherguy23]

Did you just dislike the idea of building a bridge or floor-bridge over the river to cross it? Then restrict the other lengths of the river...although they might just ignore restrictions at times. Removing the floors should turn it back to normal, but maybe not as flooring and removing can remove certain things if I remember. You can also build wall grates to stop enemies going through your plumbing

[andrian]

I just didn't like my dwarves and visitors swimming in the river. I figured that since they were pathing through it instead of going around, a bridge wouldn't exactly help. Indeed, even as I was building the floors, my dwarves were still traveling through the river for various reasons.

While I appreciate dwarves who are dedicated to learning to swim, it's dangerous for them to do it in an uncontrolled environment outside the fortress.

[Fleeting Frames]

To the OP, only actual "river" tiles in surface river biome will catch rain/provide river fish (notably excluding rivers caved in to lower z-level so that you might fish from a pond underground)

although they might just ignore restrictions at times.

Visitors ignore pathing "restrictions", yes

[mikekchar]

However, IIRC, if you retire and unretire, ponds and rivers restore their original setting.  I don't exactly know how it works because I haven't tried it, but I recall people saying to be wary of drained ponds because they will fill back up again.

[andrian]

Well, my science project is underway. The underground tree farm has been flooded thanks to the hard work of my pump and lever operators (special thanks to the bridge builders who enabled sectioning the tree farm to ensure minimal evaporation and atomize the unwanted water once the process was finished), and now I am pumping water into my still floored-over river. So far, I have not seen any fish in the river, but it's still early days yet. The water is maxing out at a depth of 3/7, which is not as high as it was. I'm uncertain as to whether this level can be increased with our current pump output. I would like to at least get a few tiles of 7/7 water to fully test the conditions under which fish will spawn.

Out of curiosity, can building destroyers take out pumps from the outlet side, or do they have to reach the spot where the pump operators stand in order to deconstruct the pumps? This will affect the design of future experiments.

[Fleeting Frames]

They have to be able to reach the pumping square. You can use this to make building-destroyer safe windmills, as ones hanging in mid-air are not able to be pathed to.

I recall vjek using this with a thin world (~15?z to magma) once by building a line of 10 pumps drawing from the magma sea and pumping over downstairs back into sea, with 8th one having pressure plates on them (made by building floor on downstairs, building plate, then deconstructing floor) to melt goblin sieges.

[PatrikLundell]

As far as I understand the condition to destroy a building is to be able to stand two tiles away from it perpendicularly with a path up to it (and I think that path can be from behind as well). If that is correct and multi tile buildings are represented by all their tiles (any of the tiles can be targeted), then you'd need to hoist the pump up in the air to protect the exposed pump tile, and make sure the tile two tiles away from the pump is unavailable either by being blocked by a wall or similar, or by being in the air. It might be possible to protect a pump by ensuring the ground it is placed on only has a single free tile in front of it to make it impossible to stand two tiles away, but I wouldn't bet on it, and if it does work, you'll get your embark fouled up by building destroyers caught on the tile outside of the output tile unable to break the incredible attraction of a destructible building unless you can present them with some juicy live bait (like stupid outpost liaisons who just have to path by near the Titan).

[andrian]

Okay, so after a period of prolonged testing, I have concluded that water depth has nothing to do with whether fish spawn in my river. I'm guessing the tiles need to be marked as being outside. I suppose this means that I will have to find some other means to prevent my visitors from swimming in the river. My current plan is to deconstruct the floors and replace them with a wall surrounding the river. Preventing anything coming in through the plumbing shouldn't be too difficult, but I will have to leave an escape route for anyone who happens to fall into the river from atop the walls, as I'm sure someone will do at some point. Being able to dry up the river is useful, however, so I should probably test whether raised (or lowered) drawbridges will interfere with rain collection and fish spawning. If a raised drawbridge will not prevent these things, but a lowered one will, this will provide an easy way to collect corpses items that end up in the river.

[PatrikLundell]

Drawbridges do not generate "inside" below them, nor do they block trees from maturing below (won't happen to you as I think river beds do not support sapling in the same way murky pools do not allow growth. Maturing trees poke through the bridge without harming it, and some logs end up on top of the bridge when the tree is cut, while some appear below). I have no idea of how it affects rain collection, though (but bridges keep evil rain from falling through them). However, it's odd that a river should depend on rainfall, as rivers typically are filled by water entering from upstream off map, but if you're settled at the source (the "fingers" pattern) things may be different.

[andrian]

I did indeed settle at the source of the river, though there's no fingers pattern. It just starts at the edge of the one biome, and seems to be behaving like a murky pool that just happens to flow off the edge of the map.It's probably an artifact from having a tundra next to a tropical shrubland. I was very surprised when the river dried up, as I've never had that happen before. Trees won't be a problem, as saplings don't seem to grow on riverbeds.

[Foxite]

By the way, the next time this pathing problem occurs, it might be better to set the traffic designation [d -> o] for the river to [r]estricted and the designation for the bridge to [h]igh.

[PatrikLundell]

As been mentioned, visitors, merchants, invaders, etc. ignore traffic restrictions. Residents only obey traffic restrictions mathematically, i.e. they'll readily cross over restricted terrain if the weight adjusted detour is costlier, so you need a lot of bridges for the residents (or pull the restricted movement cost up, which is said to have negative effects on performance).

[Fleeting Frames]

Hm, haven't read that yet. I've set mine to 99 for restricted. That bad?

I have no idea how to search for it without bringing up hundreds of threads and posts on how using traffic restrictions improves fps.

[PatrikLundell]

I have no first hand experience of large path costs. However, from d_init.txt: "If you make the last numbers too large, pathfinding might lag."
My speculation is that pathfinding knows that a geometrically longer route cannot have a cost lower than the distance, so large values would cause the algorithm to consider longer routes (i.e. more alternatives).