I see mudbricks as lower "level" than wood. Wood is an exhaustable resource, and biome-dependant. To my mind the construction quality goes: mudbrick => wood = > stone
Rivers will be used when boats are implemented, which may be awhile.
yeah true, regarding the process mudbricks are easier than wood. I was expressing it wrong. I meant that mud is in reality also dependant from the environment. As I said, Babylon could use it in large quantities, with two rivers in the area and a hot climate it offered the perfect solution for buildings. Also with burning mud/clay to ceramic it had a good point. In Egypt and Crete it was different. So they changed to wood or combined wood and mud as material.
So Rivers are a great place for the future :)
Well I can imagine that ships will take a while to implement, take your time :D