Mapping the marsh

I've been working on the big map for the Devouring Marsh during my off time while binging Celebrity Family Feud, which somehow doesn't get old even though it's the same thing each and every time, and thought I would share some of the details / struggles. 

We have 4 images here, each numbered so we can be sure what we're talking about, and we'll talk a little about what's happening in each of these.

#1 - Swampside
Here we have the town of Swampside and the 4 different terrains it sits next to.

• Forest 
• Plains
• Wetlands
• Swamp

I think we all know what forests and plains are, so we'll skip over that, but let us talk for just a moment about the Wetlands vs Swamp we see in this picture. Actually, we see 3 different types of swamp/marsh/wetlands here, but Swampside only borders 2 of them. By the way, there are very specific technical terms for Swamp, Marsh, Bog, Fen, Wetland, etc. that we are mostly going to be ignoring. These real definitions deal with composition, ph level, type of plan covering, etc. while we are primarily concerned with navigability of terrain. The terms and definitions we'll be using are as follows:

• Wetlands: The ground is mostly stable and traversable. There may be pools, ponds, and streams with lots of muddy areas, but overall this area can be navigated on foot without great challenges. On the map, Wetlands look like swamp trees without reeds.
• Swamp: This terrain type indicates an area of consistent water that would be difficult or impossible to navigate on foot. Swamps for our purposes are similar to shallow lakes. The best way to get around is by boat. There may be trees growing out of the water, there may be islands of land, and there will certainly be all sorts of aquatic creatures. On the map, Swamps look like water and reeds without swamp trees.
• Marsh: Between Wetlands and Swamp we have Marshes. These can indicate the terrain alternates between Wetlands and Swamp very frequently, or the terrain has large areas of very shallow water where one might have to wade to the knees or hips to cross. On the map, Marshes look like trees and reeds intermixed. 

This means that the people of swampside have access to a diverse set of wilderness. They can graze in the grasslands, they can hunt, trap, and gather in the woods, they can fish in the swamp, and they can hunt and gather in the wetlands. Furthermore, the swamp near Swampside is just the tail end of a much larger body of water that stretches deep into The Devouring Marsh. It is an excellent access point if one wanted to head out into the wilds.

#2 - Forest Edges
The edges of forests are always awkward areas when mapping. One of the things that makes sense to me is to have these little tendrils of trees reaching out instead of a solid wall. In my brain this makes sense as an area where the land is a little lower and the water table is a little closer to the surface and so vegetation can thrive a bit better. The area between tendrils of forest would be slightly higher, like the very gentle and broad hill or the space between ravines. If you go to  33.65436, -100.17086 on google maps you'll get an idea for what I'm talking about.

The other interpretation is the exact opposite. That these are areas of higher ground where the soil has been more eroded and the distance between top soil and a rock layer is thinner and the trees have better access to water, while the areas between have been filled in with enough erosion and sediment that the water level is more deeply buried.

I'm no geologist, hydrologist, or botanist, and I'm sure there is enough variability in the world that both interpretations have correct instances, and at the end of the day this is a fictional, magically created world so the real world mechanics are less pressing, but that's how it works in my brain. Also it just looks nicer than a forest with straighter borders, and that's what really matters.

#3 - Swamps
This picture gives a much better look at what I mean by Swamp vs Marsh vs Wetlands. The center of this image is dominated by swamp, big open areas of water with a few trees sticking out. The borders are marked with reeds. There are a few islands in this big swamp lake which are mostly marked as Wetlands, no reeds. The areas outside the Swamp are mostly Marshes, where the trees and reeds are intermixed.

Overall, I'm still working on how I want this stuff to look, and the much bigger issue of scaling that we're about to get to in #4. The Devouring Marsh is a lovely little hellhole of difficult to navigate terrain. Someone wanting to cross from one side to the other would have to carry a boat with them, which gets very awkward when the ground is soft and the vegetation is overgrown. To be more efficient, you'd want to travel by boat for as much area as possible, but may the gods help anyone whose boat is tipped or sunk. </3

#4 - Problems of scale and information
The maps I make use a scale of 10px to the mile. A single, small, swamp tree might be 14px wide and 21px tall, which means that any details that show up on the map are going to have to be on the scale of miles across. In this image, there's a big lake. Overall it's ~310x310, that is 31 miles across in both directions. That's half the width of Lake Michigan. I don't actually want my swamp lake to be that big, but it is difficult to indicate terrain features unless they are quite large.

In fact, doing some quick and dirty math, the Devouring Marsh is larger in area than any real world wetlands. The Pantanal is the world's largest wetlands/flooded grasslands and is roughly 65,000² miles. The Devouring Marsh is roughly 78,000² miles.

Lastly we have an issue of information availability. When our PCs have a map of the area at hand, they'll get a really good idea of what is around them. That's super useful when playing our games, but it does reveal a ton of information that characters most certainly wouldn't have access too. Figuring out what part of the Devouring Marsh might be crossable or where waterways might lead would be highly specialized information that was gained at the cost of many lives. This info would be held in the hands of hardened locals, and wouldn't be communicable to other people. How could you possibly instruct someone on how to navigate an area teeming with life and growth, but no good landmarks and no GPS? 

Yet if we plop a map in front of the players, they're instantly going to see that there's a big ol' circular lake in the middle of the marsh, and that lake has a circular island in the middle of it, and boy doesn't that look interesting? Maybe something's there? We should check that out. Players will see it and be interested, but characters would have no way of knowing. You'd have to be a flying creature to even be aware such a thing existed. 

So how do we detail the terrain in a way that doesn't reveal the secrets of our world? I'm still working on the answer, but my placeholder solution is to give players bad maps that don't show those details, or to block out the inside of the swamp with darkness and say "nobody knows what's happening in the swamp beyond 5 miles from the border".

That's it for now, and as always, details posted here are subject to change before final publications. These are the in-progress notes and ideas, and are likely to get updates. 

gl hf
Neal