therefore - for the reason given in Isa 8:6, the Assyrian flood, which is first to overflood Syria and Samaria, shall rise high enough to reach rebel Judah also (Isa 8:8).
the river - Euphrates swollen in spring by the melting of the snow of the Armenian mountains (compare Isa 8:6; Isa 7:20).
all his glory - Eastern kings travel with a gorgeous retinue.
channels - natural and artificial in the level region, Mesopotamia.