You could also have the canals running directly through the city (or connecting inside it in a variety of ways). Keeps the water flowing through, so it stays fresher, basically. From Sumerian archaeology (albeit very little's been done on this aspect), harbours in the cities could well have been placed a bit like market places - wherever there was convenient space and a couple of canals (or more) met, say. Water transport was just so vital for bulky, heavy or large cargoes there (e.g. nearly all timber had to be imported), it's arguable their canals and waterways were more important than the roads. Rulers seemed always to comment on having improved, or "built" (usually meaning something nearer "rebuilt" or "repaired" in many cases, given how many different rulers claimed to have "built" the same thing over time), with rather less emphasis on roadworks, beyond making them safe for travel (i.e. keeping the bandits away). That's probably too historically/archaeologically "real" for this setting, however 😁!

Happy I could help a little!

For a "proper" Sumerian settlement though, you need some canals passing through it, and maybe a bit less city planning 😉!

You can certainly get an effect like that just using the normal DD3 symbols and drawing tools. I did something of the sort for Wyvern Citadel in the Community Atlas in 2021. The Forum topic on that's here, which gives an idea as to how I arrived at the final concept. That's shown on this shot of the ground level of the fortress (which shows the cliff lines the clearest):

There are higher res versions of all the maps in my Gallery, while you can pick up copies of the Atlas FCW files for the drawings here.

Glad the shaded relief concept has helped - and very nicely executed too!

In case you haven't seen it, there is this Annual issue that deals specifically with watercolour-look map designs using CC3+ too. You may also get more ideas on this theme by searching through posts on the Forum by Lillhans, who was for some time our resident expert on creating this type of drawing style.

Shaded relief might be the way to go to be more convincing on the higher or more rugged terrain. There's this Cartographer's Annual from 2008 that would help in that regard, if you have it, or if not, try this free PDF tutorial by HadrianVI from 2017, elsewhere on this Forum.