Make a map sized 32x32 using Sunken Ruins tileset. Set the initial cliff level to 3-4 and initial water level to shallow water.
Firstly, untick the Enforce Water Height Limits.
Step 1 – Making the base for the river
After creating the map, you see a map full of water. Select „Increase one” tool and raise the whole map map. This looks something wierd to do, but its not.
Step 2 – Making the river
Now, select lower tool and start carving the river itself. Lower the terrain until you see water popping out. Make a nice curved river.
TIP: use smooth tool on the shores to get rid of squariness.
If you dont use this tehnique and simply lower the terrain you get something like this. Pretty squared and not natural eh?
Step 3 – Making some hills
For hills, use the raise tool. Make some medium sized hills around the river. The map isnt very big, so little hills are better than big ones. If you want to use this tehnique on a bigger map, Obiusly bigger mountains give a better effect.
Step 4 – Adding trees
Pick some Canopy and Ruins trees and use them on the little hills you created. Leave the shores untouched, because we need them for doodads.
Step 5 – Enviroment
To give the map a jungle like looking, select some eviromental doodads like bushes, cactails, rocks and lily pads and use them to create a jungle. Apply them to the forest, as well on the water itself. Shrub is one of my favorite doodad, when it comes to making jungles. Use it on the trees to achieve the jungle look. (Vines are also good).
Step 6 – Final Touch
As you can see, there is something missing. All the jungle rivers tend to be green instead of blue. Its because of their muddy base. Set the water tinting to dark green. Much better!
Also, I add some wild boars, running wild in the spooky jungle…Probably chased by those nasty murlocs.
TIP: Using rain weather effects gives the jungle more natural feeling.
Optional Step - Making the river uncrossable by ground units
To make it uncrossable, select the doodads and find pathing blocker (ground). Then apply it to the both shores of the river.