And it happened under the shadow of a great rock, in a cleft, green-grown and sheltered, where the road runs beside the noisy, stony, rapid, unnavigable river.
"The Literary Sense"
E. Nesbit
I am led to form this opinion, partly from having seen no shipping at the wharfs, and partly because the Adour, though here both wide and deep, is rendered unnavigable to vessels of any size, by a shallow or bar at its mouth.
"The Campaigns of the British Army at Washington and New Orleans 1814-1815"
G. R. Gleig
Moreover, it comes then in such heavy storms that for some hours, or even days, the streams are so swollen as to be not only impassable by waggons, but also unnavigable, because, although there is plenty of water, the current is too violent.
"Impressions of South Africa"
James Bryce