Mixed land/water trade routes?

Puttering around with trade routes still, I’ve decided to use Dwimmermount as my example.

This is a little stream-of-thought.

Given the demand of markets based on their population, I note Adamas is not well-served by it’s environs, and (by my reckoning, at least) has a trade deficit - that is, if each market is trading to each of it’s trade partners based on the overall ratio of the target market demand to the overall demand of it’s trading partners, Adamas isn’t getting enough trade into it to meet it’s demand.

The easy answer, since Adamas is on a river, is “off map markets”. We’re well within the 60 hex range of water trade for a Class II market off-map along the Lanis or Fyris rivers. Retep City is in the same boat, though landlocked, and is a hex off the map edge.

That little curve on the Vagar River…hex…15xx where it takes a right after coming south (the hex markers on the map in the PDF are damnably hard to read)

A little stronghold right there equipped to offload river barges onto wagons could make it to Retep City from Adamas.

~21 hexes of river, then another ~7 hexes of land travel is well within the travel budget for a Class II.

There’s got to be some historical basis on this sort of a thing?

What sort of stronghold & garrison would it take to secure that trade? Base it on the amount of trade coming through perhaps (take the amount in stone, translate it back to population via demand-per-family, then stronghold & garrison size would be determined by that false population number?) Also; what does a river barge merchant look like on the MS&C table;pg145?

Is the profit involved from trade something worth spending on a stronghold+garrison (maybe it’s paid for by a merchant cartel rather than the domain ruler…?)

How much would something like this mess up any assumptions in ACKS about trade routes, if one did this?

It seems like it’d eventually become it’s own domain, as the activity at the “market hub” would tend to attract workers and therefore settlers; but once it’s an official domain, it’s technically no longer a valid trade route.

Or is this all too gamey?

Makes sense to me. I’d say work out some kind of formula for converting sea-miles into land miles (Is the trade route distance ratio consistent?) with a penalty because switching between them is a nuisance.