Won't the land tremble for this, And everyone mourn who dwells in it? Yes, it will rise up wholly like the River; And it will be stirred up and sink again, like the River of Egypt.
It will be noted that "River" in the first part of this verse is definitely not referred to as the "River of Egypt."  Also, the fact that Assyria is clearly in the mind of Amos throughout this prophecy adds to the probability of their being two rivers in view.  In that case, it would mean that the River (Assyria) would overflow against Israel in a manner ("as") like the well-known innundations of the Nile, "of Egypt" in that case being the identification of the river to which comparison was made, and not an identification of the first river.