Terrain Hazards: Sewers

This is about where I quit
from boredom.

All the big cities got them, sewers! Sewers are kinda gross, but somehow, video games make us walk through them once per RPG at least it seems. You know what kind of enemies to expect when walking through a sewer, of course, and probably know the motive for going through a sewer, but what can be added to a fight in GURPS to make it interesting? Let's try coming up with some ideas.

Narrow Walkways

A typical absurdly spacious sewer has really narrow walkways on either side of a canal so that someone can avoid falling in the muck and grime. This situation makes it hard for a large party to fight all at once, and hampers dodging ability. Pay attention to knockback rules when implementing narrow walkways. Throwing, or being thrown into the depths below might be possible if the ledge is only a yard wide. Likewise, slam damage into the wall beside or allies behind is also a possibility.

The most horrific possibility is being grabbed by an ankle and being pulled in. Check rules for grappling to see how something might do this.

Sewer Juice

Sewage is gross.  Having it smeared on the walkways might give an easy DX roll penalized for speed to not slip. The ankle deep variety might penalize move a little, and the waist deep variety might penalize it a lot. Check p.387 of Basic Set - Campaigns for more options.

Smell

In the aerobic act of performing combat breathing is heavier, and smelling and tasting become more likely. This might require sudden HT rolls, possibly penalized for acute senses, or waived for doesn't breathe. Likely afflictions in a sewer might be:

• Coughing
• Nauseated
• Choking
• Retching

Those are roughly ordered from least to greatest impact. These might strike at any time during combat in a sewer. You might say that the contest is only to be afflicted with one issue, or call it by degrees of failure; eg, maybe failure is Coughing, Failure by 2 is nausea; failure by 4 is choking; failure by 6 is retching.

Sluice

Controlling the flow of water during combat can be an interesting mechanic that might be possible for strong characters or someone with access to a crank controlled lock. I can't even begin to think of numbers, but I'd imagine it might take ten turns of ready maneuvers to lift a gate so far that it would have a noticeable effect, probably another ten turns to completely open the flood gates, but a fantasy world civil engineer can correct me if I'm wrong. Doing this might sweep away anything submerged, for good or for bad, as the area drains.

Inversely, closing a lock might allow an area to eventually fill, but probably much slower than it could become empty. This could be used as a setup for a trap later, to deluge an opponent with a flood.

This might make a situation where protecting someone attempting to operate the lock, or stopping someone from opening the lock becomes an important battle objective, enabling tactics that are normally overlooked in the name of resolutely keeping people out, or breaking through at all costs.

Other Thoughts and Closing

Sewers again, I feel like are more about what they enable from a story telling perspective, rather from a battle perspective. Sewers are the weird way in fiction that we break into castles or out of prisons because there are sewers everywhere. It seems like they are rarely the goal or the outright objective and more of a means to an end; we don't say, "I'd love to go to the sewer," we say, "unfortunately, the sewer is the best way to do some other thing that we want to do." There are exceptions though. We can have sewer people, or an underground secret hideout sometimes. It's also an option for a secret rendezvous where we can go without having annoying interlopers, and we don't even need to leave the city limits.

Realistically, the health hazards of sewer gas can approach the one of natural gas in mines, I've heard (correct me if I'm wrong,) but fantasy characters can wade through it like nothing. A realistic sewer probably has a very regular pattern of long, straight tunnels, and almost no large rooms and probably very few doors, but a barred gate here or there might exist? Dunno. I don't think about sewers when I think about adventures. Maybe I should try?