I've tried to line these up so you can see how the river is shaping up in one go. Not sure how it will display in different browsers...
Here I've started expanding the Mssúma river floodplain. It was bothering me that it was so uniform and narrow. I don't think it would be in a real world. So I pushed it back in a few spots, and added areas where the elevation is high enough that they end up as islands when the river is in full flood. Not that they are necessarily "hills" as such, just enough of a rise to avoid the flooding. Of course, this would vary from year to year. I remember reading a bit about the Sikh wars and I seem to recall all the towns and villages being up on mounds or hilltops.
In the bottom picture I've added another lake. This lake is there all year round but during the floods it expands to over 5 or 6 times its size! I've actually gone a bit further than this, sketching in islands and ox-bow lakes as well as secondary channels. I've also started penciling in some lesser tributaries. Hopefully I'll be able to show you these in a day or two.
Part of my reason for adding the lake is to give a reason for the sákbe road to curve to the west like it does. Why wouldn't it go as straight as possible across the river bend? And there are not enough lakes shown on the large maps anyway. What are there - three, maybe four, in the whole map set?
I've also started to think about how fiefs might be distributed in this new terrain, and who owns what. Well, we know the Emperor "owns" everything, but who are the fief-holders. These will include the temples as well as the clans and nobles. I'll have to look up where each province is administered from as well.