Boats were commonly found in sufficient numbers on the streams themselves when an army needed them, and were impressed, or hired, to convey the troops across.

And thus we see that the actual navigation of the streams had another object besides the military one of transport from bank to bank.

Rivers are Nature's roads; and we may be sure that the country had not been long settled before a water communication began to be established between towns upon the river-courses, and commodities began to be transported by means of them.
The very position of the chief towns upon time banks of the streams was probably connected with this sort of transport, the rivers furnishing the means by which large quantities of building material could be conveniently concentrated at a given spot, and by which supplies could afterwards be regularly received from a distance.

We see in the Assyrian sculptures the conveyance of stones, planks, etc.

along the rivers, as well as the passage of chariots, horses, and persons across them.